Factors relating to nonpublication and publication bias in clinical trials in Canada: A qualitative interview study.

AIMS: This study aims to understand factors contributing to nonpublication and publication bias in clinical trials in Canada. METHODS: Qualitative interviews were conducted between March 2019 and April 2021 with 34 participants from the Canadian provinces of Alberta, British Columbia and Ontario, including 17 clinical trial investigators, 1 clinical research coordinator, 3 research administrators, 3 research ethics board members and 10 clinical trial participants. We conducted a thematic analysis involving coding of interview transcripts and memo-writing to identify key themes. RESULTS: Several factors contribute to nonpublication and publication bias in clinical trial research. A core theme was that reporting practices are shaped by incentives within the research system taht favour publication of positive over negative trials. Investigators are discouraged from reporting by experiences or perceptions of difficulty in publishing negative findings but rewarded for publishing positive findings in various ways. Trial investigators more strongly associated positive clinical trials than negative trials with opportunities for industry and nonindustry funding and with academic promotion, bonuses and recognition. Research institutions and ethics boards tended to lack well-resourced, proactive policies and practices to ensure trial findings are reported in registries or journals. CONCLUSION: Clinical trial reporting practices in Canada are shaped by incentives favouring reporting of positive over negative trials, such as funding opportunities and academic promotion, bonuses and recognition. Research institutions could help change incentives by adopting performance metrics that emphasize full reporting of results in journals or registries.

Pioglitazone use in Australia and the United Kingdom following drug safety advisories on bladder cancer risk: An interrupted time series study.

PURPOSE: National regulators in Australia and the United Kingdom issued safety advisories on the association between pioglitazone use and bladder cancer in July 2011. The Australian advisory noted that males were at higher risk of bladder cancer than females, while the UK advisory highlighted a new recommendation, suggest careful consideration in the elderly due to increasing risk with age. This study examined whether these differences in the advisories had different age- and sex-based impacts in each country. METHODS: Interrupted time series analysis was used to compare pioglitazone use (prescriptions/100000 population) in Australia and the United Kingdom for the 24 months before and 11 months after the July 2011 safety advisories (study period July 2009-June 2012). Separate models were used to compare use by sex and age group (≥65 years vs. <65 years) in each country. RESULTS: Pioglitazone use fell in Australia (17%) and the United Kingdom (24%) following the safety advisories. Use of pioglitazone fell more for males (18%) than females (16%) in Australia, and more for females (25%) than males (23%) in the United Kingdom; however, neither difference was statistically significant (Australia p = 0.445, United Kingdom p = 0.462). Pioglitazone use fell to a similar extent among older people than younger people in the United Kingdom (23% vs. 26%, p = 0.354), and did not differ between age groups in Australia (both 18%, p = 0.772). CONCLUSIONS: The results indicate that differences in the Australian and UK safety advisories resulted in substantial reductions in pioglitazone use at the population level in both countries, however, differences by sub-groups were not observed.

Comparative Safety of Smoking Cessation Pharmacotherapies During a Government-Sponsored Reimbursement Program.

INTRODUCTION: The British Columbia Ministry of Health launched a Smoking Cessation Program on September 30, 2011, providing financial coverage for smoking cessation pharmacotherapies. Although pharmacotherapies have been shown to have a moderate short-term benefit as a quitting aid, substantial cardiovascular and neuropsychiatric safety concerns have been identified in adverse-reporting databases, leading to prescription label warnings by Health Canada and the U.S. Food and Drug Administration. However, recent studies indicate these warnings may be without merit. This study examined the comparative safety of medications commonly used to aid smoking cessation. AIMS AND METHODS: Population-based retrospective cohort study using B.C. administrative data to assess the relative safety between varenicline, bupropion, and nicotine replacement therapies (NRTs). The primary outcome was a composite of cardiovascular hospitalizations. Secondary outcomes included mortality, a composite of neuropsychiatric hospitalizations, and individual components of the primary outcome. Statistical analysis used propensity score-adjusted log-binomial regression models. A sensitivity analysis excluded patients with a history of cardiovascular disease. RESULTS: The study included 116 442 participants. Compared with NRT, varenicline was associated with a 10% 1-year relative risk decrease of cardiovascular hospitalization (adjusted risk ratio [RR] = 0.90, 95% confidence interval (CI): 0.82 to 1.00), a 20% 1-year relative risk decrease of neuropsychiatric hospitalization (RR: 0.80, CI: 0.7 to 0.89), and a 19% 1-year relative risk decrease of mortality (RR: 0.81, CI: 0.71 to 0.93). We found no significant association between NRT and bupropion for cardiovascular hospitalizations, neuropsychiatric hospitalizations, or mortality. CONCLUSIONS: Compared with NRT, varenicline is associated with fewer serious adverse events and bupropion the same number of serious adverse events. IMPLICATIONS: This study addresses the need for comparative safety evidence in a real-world setting of varenicline and bupropion against an active comparator. Compared with NRT, varenicline was associated with a decreased risk of mortality, serious cardiovascular events, and neuropsychiatric events during the treatment, or shortly after the treatment, in the general population of adults seeking pharmacotherapy to aid smoking cessation. These results provide support for the removal of the varenicline boxed warning for neuropsychiatric events and add substantively to the cardiovascular safety findings of previous observational studies and randomized clinical trials.

Medications to reduce emergence coughing after general anaesthesia with tracheal intubation: a systematic review and network meta-analysis.

BACKGROUND: Emergence coughing can harm the patient following completion of surgery, but it is unclear which medication is most effective at reducing this event. We conducted a systematic review and network meta-analysis of RCTs to determine the medications' relative efficacies on decreasing moderate to severe emergence coughing after general anaesthesia. Medications studied were lidocaine (i.v., intracuff, topical, or tracheal application), dexmedetomidine, remifentanil, and fentanyl. METHODS: We searched eight different medical literature databases, conference abstracts, and article references. After screening, included citations were evaluated for bias and had their data extracted. Pooled odds ratios and 95% confidence intervals for each treatment comparison were calculated. A surface under the cumulative ranking curve analysis (SUCRA) determined the relative rank of each intervention to decrease moderate to severe emergence coughing. Subgroup analyses included severe coughing only, extubation times, type of maintenance anaesthetic, and dosages. RESULTS: The network meta-analysis included 70 studies and 5286 patients. All study medications had favourable odds in reducing moderate and severe peri-extubation coughing compared with either no medication or placebo. No single medication was favoured over another. Dexmedetomidine had the highest SUCRA rank, followed in order by remifentanil, fentanyl, and lidocaine via intracuff, tracheal/topical, and i.v. routes. Remifentanil was ranked highest for decreasing severe coughing only. Intracuff lidocaine had higher odds of prolonging extubation times compared with placebo, dexmedetomidine, fentanyl, and remifentanil. CONCLUSION: All study medications were better than placebo or no medication in reducing moderate to severe emergence cough, with dexmedetomidine ranked the most effective. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration number: CRD42018102870.

A rapid monitoring plan following a shift in coverage from brand name to biosimilar drugs for rheumatoid arthritis in British Columbia.

PURPOSE: To describe a rapid monitoring plan to assess the impacts of a shift in drug coverage for biosimilar drugs in British Columbia following the introduction of a new policy on 27 May 2019. The Biosimilars Initiative requires users of originator infliximab or etanercept to switch to biosimilar versions of those drugs to maintain coverage. We propose a signal-detection method to provide near-real-time information to policymakers on the impacts of the policy change. METHODS: The exposure will be the Biosimilars Initiative, a policy affecting patients using originator infliximab (Remicade) and etanercept (Enbrel) for approved rheumatologic or dermatologic indications. Two policy cohorts and six historical control cohorts of patients using originator infliximab or etanercept will be assembled using linked and de-identified data from the British Columbia Ministry of Health. Patients will be identified during the 6-month period before the policy anniversary. Outcomes will include medication refills and switching, hospital admissions, emergency department visits, and physician visits. Summary outcome measures, such as cumulative incidence or average quantity as applicable, will be examined daily and reported monthly for 1 year. Outcomes in the policy cohorts will be compared with historical controls using likelihood ratios. RESULTS: The results of this rapid monitoring plan will be based on analyses involving approximately 9000 patients: four infliximab cohorts of approximately 430 patients and four etanercept cohorts of approximately 1800 patients. CONCLUSIONS: Rapid monitoring results will inform ongoing policy decisions related to the Biosimilars Initiative, in terms of impacts on both patient health and health services utilization.

Identifying sequential episodes of pharmacotherapy as a method for assessing treatment failure in comparative effectiveness research.

PURPOSE: To describe and implement a novel method of measuring comparative effectiveness using sequential episodes of pharmacotherapy as a proxy for treatment failure. METHODS: Retrospective cohort study using linked deidentified data from the British Columbia Ministry of Health during a government-sponsored smoking cessation reimbursement program.Three study cohorts were created based on first use of varenicline, bupropion, or nicotine replacement therapy (NRT), for adults aged 18 or older, in the period September 30th, 2011 to March 31st, 2013. The study cohorts were analyzed for sequential episodes of pharmacotherapy, defined as re-initiating a smoking cessation pharmacotherapy after an initial episode of treatment and washout period. The statistical analysis used propensity score adjusted log-binomial regression models with one-year and two-year fixed follow-up after a 12-week washout period. A sensitivity analysis excluded the washout period. A secondary analysis investigated predictors of receiving a sequential episode of smoking cessation pharmacotherapy RESULTS: 116,442 participants of the B.C. Smoking Cessation Program were analyzed. Compared to NRT, varenicline users were 13% less likely, and bupropion users were 18% less likely, to re-start smoking cessation therapy within 1-year after an initial course of treatment. CONCLUSIONS: Sequential episodes of pharmacotherapy identified treatment failures to smoking cessation therapy. Based on sequential episodes of pharmacotherapy during a drug benefit policy of smoking cessation medications, varenicline and bupropion were more effective aids to smoking cessation than NRT. The method was also used to identify patient characteristics associated with treatment effectiveness.

A theoretical exploration of therapeutic monomania as a physician-based instrumental variable.

PURPOSE: To explore the utility of physician prescribing preference as an instrumental variable. METHODS: Expert (non-systematic) review of relevant literature on the appropriate selection of instrumental variables and theoretical exploration of individual physician and physician group prescriber preference. RESULTS: An instrumental variable must satisfy three criteria: (1) It must predict the treatment received (strength of the instrument); (2) it cannot influence the outcome other that through the treatment received (exclusion restriction); and (3) it cannot be influenced by any factor that also influences the outcome (independence assumption). Arguments in favor of prescriber preference as an instrumental variable and suggestions for how to approach specific scenarios that may be encountered are offered. CONCLUSIONS: Prescriber preference, be it of individual physicians or groups of physicians, may, under the right conditions, be powerful instrumental variables. Empiric experimental data are required to determine the appropriateness of combining propensity matching and instrumental variable analysis.

Rapid monitoring of health services utilization following a shift in coverage from brand name to biosimilar drugs in British Columbia-An interim report.

PURPOSE: We explored changes in health services utilization associated with the Biosimilars Initiative introduced in British Columbia on May 27, 2019. To maintain drug coverage, the policy requires users of originator infliximab or etanercept to transition to biosimilar versions. We present a three-month interim analysis of this initiative. METHODS: We conducted a rapid monitoring analysis to evaluate changes in health services utilization three months after the policy was introduced compared with a three-year period before the policy's introduction. Using the administrative claims data of the British Columbia Ministry of Health, we assembled three historical cohorts and one policy cohort of users of each originator drug (8 cohorts in total). Cumulative incidences of medication refills, switching, and visits to physicians were the outcome measures used to compare policy and historical cohorts. Likelihood ratios were used to quantify statistical differences between each policy cohort and its respective historical controls. Likelihood ratios above 7.1 were considered statistically significant. RESULTS: The four infliximab cohorts included 436 patients on average, mean age 56 to 59, 53% to 55% females. The four etanercept cohorts included 1826 patients on average, mean age 57 to 58, 60% to 63% females. Three months after the policy's introduction, 21% of patients treated in the policy cohorts transitioned to the biosimilar versions. Health services utilization in the policy cohorts were consistent with the historical cohorts. CONCLUSIONS: An increase in visits to physicians was expected but not detected in the first three months of the Biosimilars Initiative. The impacts of the policy will continue to be monitored.

Measuring the impact of pharmacoepidemiologic research using altmetrics: A case study of a CNODES drug-safety article.

PURPOSE: To provide an overview of altmetrics, including their potential benefits and limitations, how they may be obtained, and their role in assessing pharmacoepidemiologic research impact. METHODS: Our review was informed by compiling relevant literature identified through searching multiple health research databases (PubMed, Embase, and CIHNAHL) and grey literature sources (websites, blogs, and reports). We demonstrate how pharmacoepidemiologists, in particular, may use altmetrics to understand scholarly impact and knowledge translation by providing a case study of a drug-safety study conducted by the Canadian Network of Observational Drug Effect Studies. RESULTS: A common approach to measuring research impact is the use of citation-based metrics, such as an article's citation count or a journal's impact factor. "Alternative" metrics, or altmetrics, are increasingly supported as a complementary measure of research uptake in the age of social media. Altmetrics are nontraditional indicators that capture a diverse set of traceable, online research-related artifacts including peer-reviewed publications and other research outputs (software, datasets, blogs, videos, posters, policy documents, presentations, social media posts, wiki entries, etc). CONCLUSION: Compared with traditional citation-based metrics, altmetrics take a more holistic view of research impact, attempting to capture the activity and engagement of both scholarly and nonscholarly communities. Despite the limited theoretical underpinnings, possible commercial influence, potential for gaming and manipulation, and numerous data quality-related issues, altmetrics are promising as a supplement to more traditional citation-based metrics because they can ingest and process a larger set of data points related to the flow and reach of scholarly communication from an expanded pool of stakeholders. Unlike citation-based metrics, altmetrics are not inherently rooted in the research publication process, which includes peer review; it is unclear to what extent they should be used for research evaluation.

Multiple imputation for systematically missing confounders within a distributed data drug safety network: A simulation study and real-world example.

PURPOSE: In distributed data networks, some data sites may be systematically missing important confounders that are captured by other sites in the network (eg, body mass index [BMI]). Multiple imputation may help repair bias in these scenarios. However, multiple imputation has not been described for distributed data networks where data access restrictions prevent centralized analysis. METHODS: We conducted a simulation study and a real-world analysis using the UK's Clinical Practice Research Datalink to evaluate multiple imputation for confounders that are systematically missing from a subset of data sites in mock distributed data networks. The simulation study addressed univariate missing data, while the real-world analysis addressed multivariate missing data. Both studies were designed as retrospective cohort studies of the effect of current statin use on the risk of myocardial infarction among patients with newly treated type 2 diabetes. RESULTS: In our simulation study, multiple imputation repaired bias from missing BMI in all scenarios, with a median bias reduction of 118% in the default scenario. In our real-world study, the multiply imputed analysis (hazard ratio [HR]: 0.86; 95% confidence interval [CI], 0.69-1.08) was closer to the analysis that considered the true confounder values (HR: 0.85; 95% CI, 0.66-1.10) than the analysis that ignored them (HR: 0.93; 95% CI, 0.73-1.20). CONCLUSIONS: Multiple imputation adapted to distributed data settings is a feasible method to reduce bias from unmeasured but measurable confounders when at least one database contains the variables of interest. Further research is needed to evaluate its validity in real distributed data networks.

Extreme restriction design as a method for reducing confounding by indication in pharmacoepidemiologic research.

PURPOSE: Confounding by indication is a concern in observational pharmacoepidemiologic studies, including those that use active comparator, new user (ACNU) designs. Here, we present a method of restriction to an indication, which we call "extreme restriction," to reduce confounding in such studies. METHODS: As a case study, we evaluated the effect of proton pump inhibitors (PPIs) on hospitalization for community-acquired pneumonia (HCAP). PPI use has been associated with increased HCAP risk, but this association likely results from confounding by indication due to gastroesophageal reflux disease (GERD). Using the UK's Clinical Practice Research Datalink, we compared the risk of HCAP within 180 days between PPI users and histamine-2 receptor antagonist (H2RA) users in an ACNU cohort using Cox proportional hazard models with a time-fixed exposure definition adjusted for high-dimensional propensity score deciles. We then performed the same analysis on an "extremely-restricted" cohort of incident nonsteroidal anti-inflammatory drug (NSAID) users, some of whom received PPIs for prophylaxis. Because PPIs were given as prophylaxis in this population, confounding due to GERD should be limited. We compared effect estimates between ACNU and restricted cohorts to evaluate confounding in both analyses. RESULTS: In the ACNU cohort, PPIs were associated with an increased risk of HCAP (hazard ratio [HR]: 1.25; 95% confidence interval [CI]: 1.05, 1.47), but this association was not present in the restricted cohort (HR: 1.06; 95% CI: 0.75, 1.49). CONCLUSIONS: Restriction to a single indication for treatment may reduce confounding by indication in studies conducted in distributed data networks and other large databases.

A population-based analysis of antidiabetic medications in four Canadian provinces: Secular trends and prescribing patterns.

PURPOSE: To use the Canadian Network for Observational Drug Effect Studies (CNODES) to describe drug utilization of antidiabetic medications in four Canadian provinces. METHODS: With the use of data from CNODES, we constructed cohorts of patients with type 2 diabetes in four Canadian provinces (Manitoba, Ontario, Quebec, and Saskatchewan) who received their first-ever prescription for a noninsulin antidiabetic medication during the study period, defined as the earliest date of data availability in each province (range: 1993-1998) to the latest date of the data extraction in each province (range: 2013-2014). Prescriptions rates were calculated for all prescriptions by class and described over time. RESULTS: Across provinces, we identified 650 830 patients who initiated antidiabetic medications during the study period. In most provinces, the overall prescription rate of antidiabetic medications increased during the last two decades. Metformin particularly increased in popularity, surpassing sulfonylureas in all provinces as the most widely prescribed antidiabetic medication by the early 2000s. Thiazolidinediones grew in popularity from the onset of their availability until 2006 to 2007, at which point they rapidly declined. Dipeptidyl peptidase-4 inhibitors saw substantial growth in several provinces following their addition to provincial formularies in 2008 to 2012, while glucagon-like peptide-1 agonists experienced modest growth. Insulin prescription rates remained constant or steadily increased over the last two decades. CONCLUSIONS: CNODES can be used for cross-jurisdictional drug utilization studies. In Canada, trends in antidiabetic medication prescriptions followed changing guidelines reflecting up-to-date knowledge of drug effectiveness and safety.

Time course for blood pressure lowering of beta-blockers with partial agonist activity.

BACKGROUND: Beta-blockers are commonly used in the treatment of hypertension. We do not know whether the blood pressure (BP) lowering efficacy of beta-blockers varies across the day. This review focuses on the subclass of beta-blockers with partial agonist activity (BBPAA). OBJECTIVES: To assess the degree of variation in hourly BP lowering efficacy of BBPAA over a 24-hour period in adults with essential hypertension. SEARCH METHODS: The Cochrane Hypertension Information Specialist searched the following databases for relevant studies up to June 2020: the Cochrane Hypertension Specialised Register; CENTRAL; 2020, Issue 5; MEDLINE Ovid; Embase Ovid; the World Health Organization International Clinical Trials Registry Platform; and ClinicalTrials.gov. We also contacted authors of relevant papers regarding further published and unpublished work. The searches had no language restrictions. SELECTION CRITERIA: We sought to include all randomised and non-randomised trials that assessed the hourly effect of BBPAA by ambulatory monitoring, with a minimum follow-up of three weeks. DATA COLLECTION AND ANALYSIS: Two review authors independently selected the included trials and extracted the data. We assessed the certainty of the evidence using the GRADE approach. Outcomes included in the review were end-point hourly systolic and diastolic blood pressure (SBP and DBP) and heart rate (HR), measured using a 24-hour ambulatory BP monitoring (ABPM) device. MAIN RESULTS: Fourteen non-randomised baseline controlled trials of BBPAA met our inclusion criteria, but only seven studies, involving 121 participants, reported hourly ambulatory BP data that could be included in the meta-analysis. Beta-blockers studied included acebutalol, pindolol and bopindolol. We judged most studies at high or unclear risk of bias for selection bias, attrition bias, and reporting bias. We judged the overall certainty of the evidence to be very low for all outcomes. We analysed and presented data by each hour post-dose. Very low-certainty evidence showed that hourly mean reduction in BP and HR visually showed an attenuation over time. Over the 24-hour period, the magnitude of SBP lowering at each hour ranged from -3.68 mmHg to -17.74 mmHg (7 studies, 121 participants), DBP lowering at each hour ranged from -2.27 mmHg to -9.34 mmHg (7 studies, 121 participants), and HR lowering at each hour ranged from -0.29 beats/min to -10.29 beats/min (4 studies, 71 participants). When comparing between three 8-hourly time intervals that correspond to day, evening, and night time hours, BBPAA was less effective at lowering BP and HR at night, than during the day and evening. However, because we judged that these outcomes were supported by very low-certainty evidence, further research is likely to have an important impact on the estimate of effect and may change the conclusion. AUTHORS' CONCLUSIONS: There is insufficient evidence to draw general conclusions about the degree of variation in hourly BP-lowering efficacy of BBPAA over a 24-hour period, in adults with essential hypertension. Very low-certainty evidence showed that BBPAA acebutalol, pindolol, and bopindolol lowered BP more during the day and evening than at night. However, the number of studies and participants included in this review was very small, further limiting the certainty of the evidence. We need further and larger trials, with accurate recording of time of drug intake, and with reporting of standard deviation of BP and HR at each hour.

A Multicenter Observational Study of Incretin-based Drugs and Heart Failure.

BACKGROUND: There is concern that antidiabetic incretin-based drugs, including dipeptidyl peptidase 4 (DPP-4) inhibitors and glucagon-like peptide 1 (GLP-1) analogues, can increase the risk of heart failure. Ongoing clinical trials may not have large enough samples to effectively address this issue. METHODS: We applied a common protocol in the analysis of multiple cohorts of patients with diabetes. We used health care data from four Canadian provinces, the United States, and the United Kingdom. With the use of a nested case-control analysis, we matched each patient who was hospitalized for heart failure with up to 20 controls from the same cohort; matching was based on sex, age, cohort-entry date, duration of treated diabetes, and follow-up time. Cohort-specific hazard ratios for hospitalization due to heart failure among patients receiving incretin-based drugs, as compared with those receiving oral antidiabetic-drug combinations, were estimated by means of conditional logistic regression and pooled across cohorts with the use of random-effects models. RESULTS: The cohorts included a total of 1,499,650 patients, with 29,741 hospitalized for heart failure (incidence rate, 9.2 events per 1000 persons per year). The rate of hospitalization for heart failure did not increase with the use of incretin-based drugs as compared with oral antidiabetic-drug combinations among patients with a history of heart failure (hazard ratio, 0.86; 95% confidence interval [CI], 0.62 to 1.19) or among those without a history of heart failure (hazard ratio, 0.82; 95% CI, 0.67 to 1.00). The results were similar for DPP-4 inhibitors and GLP-1 analogues. CONCLUSIONS: In this analysis of data from large cohorts of patients with diabetes, incretin-based drugs were not associated with an increased risk of hospitalization for heart failure, as compared with commonly used combinations of oral antidiabetic drugs. (Funded by the Canadian Institutes of Health Research; ClinicalTrials.gov number, NCT02456428.).

Policy-induced selection bias in pharmacoepidemiology: The example of coverage for Alzheimer's medications in British Columbia.

PURPOSES: To assess the impact of a government-sponsored reimbursement policy for cholinesterase inhibitors (ChEIs) on trends in physician visits with a diagnosis of Alzheimer's disease (AD). METHODS: Longitudinal population-based study using interrupted time series methods. British Columbia outpatient claims data for individuals aged 65 and older were used to compute monthly AD visit rates and examine the impact of the ChEI reimbursement policy on the coding of AD. We examined trends in the number of patients with AD visits, the number of AD visits per patient, and visits with "competing" diagnoses (mental, neurological, and cerebrovascular disorders and accidental falls). Finally, we described demographic and clinical features of diagnosed patients. RESULTS: We analyzed 1.9 million AD visits. Faster growth in recorded AD visits was observed after the policy was implemented, from monthly growth of 7.5 visits per 100 000 person-months before the policy (95% confidence interval [CI], 6.1-8.9) to monthly growth of 16.5 per 100 000 person-months after the policy (95% CI, 14.8-18.3). After the implementation of the policy, we observed increased growth in the number of patients with recorded AD visits and the number of AD visits per patient, as well as a shift in diagnoses away from mental diseases and accidental falls to AD (diagnosis substitution). CONCLUSIONS: British Columbia's reimbursement policy for ChEIs was associated with a significant acceleration in Alzheimer's visits. Evaluations of health services utilization and clinical outcomes following drug policy changes need to consider policy-induced influences on the reliability of the data used in the analysis.

Ventricular tachyarrhythmia and sudden cardiac death with domperidone use in Parkinson's disease.

AIM: Domperidone is preferentially used over other antiemetic agents to treat digestive symptoms in Parkinson's disease (PD). Concerns have been raised regarding an increased risk of ventricular tachyarrhythmia and sudden cardiac death (VT/SCD) associated with domperidone in the general population. However, the risk in PD is unknown. METHODS: We conducted a multicentre retrospective cohort study using administrative databases from seven Canadian provinces and the UK Clinical Practice Research Datalink. Using a nested case-control analysis, we estimated the rate ratios (RRs) of VT/SCD associated with domperidone use compared to no use in patients newly-diagnosed with PD. VT/SCD events were identified using administrative medical records and vital statistics with a manual review of all potential cases. Meta-analytic methods were used to estimate overall effects across sites. RESULTS: Among 214 962 patients with PD, 2907 cases of VT/SCD were identified during 886 581 person-years of follow-up (incidence rate 3.28 per 1000 persons per year). Current use of domperidone was associated with a non-statistically significant 22% increased risk of VT/SCD (RR 1.22; 95% CI 0.99-1.50) compared with no use. The risk was significantly elevated in those with a history of cardiovascular disease (RR 1.38; 95% CI 1.07-1.78), but not in those without (RR 1.21; 95% CI 0.81-1.81). Dose and duration of use did not affect the magnitude of the risk. CONCLUSION: Domperidone use may increase the risk of VT/SCD in patients with PD, particularly those with a history of cardiovascular disease. This risk may be underestimated because of imprecision in identifying VT/SCD events.

Occurrence of pregnancy and pregnancy outcomes during isotretinoin therapy.

BACKGROUND: Isotretinoin, a teratogen, is widely used to treat cystic acne. Although the risks of pregnancy during isotretinoin therapy are well recognized, there are doubts about the level of adherence with the pregnancy prevention program in Canada. Our objective was to evaluate the effectiveness of the Canadian pregnancy prevention program in 4 provinces: British Columbia, Saskatchewan, Manitoba and Ontario. METHODS: Using administrative data, we identified 4 historical cohorts of female users of isotretinoin (aged 12-48 yr) for the period 1996 to 2011. We defined pregnancy using International Statistical Classification of Diseases and billing codes. One definition included only cases with documented pregnancy outcomes (high-specificity definition); the other definition also included individuals recorded as receiving prenatal care (high-sensitivity definition). We studied new courses of isotretinoin and detected pregnancies in 2 time windows: during isotretinoin treatment only and up to 42 weeks after treatment. Live births were followed for 1 year to identify congenital malformations. RESULTS: A total of 59 271 female patients received 102 308 courses of isotretinoin. Between 24.3% and 32.9% of participants received prescriptions for oral contraceptives while they were taking isotretinoin, compared with 28.3% to 35.9% in the 12 months before isotretinoin was started. According to the high-specificity definition of pregnancy, there were 186 pregnancies during isotretinoin treatment (3.1/1000 isotretinoin users), compared with 367 (6.2/1000 users) according to the high-sensitivity definition. By 42 weeks after treatment, there were 1473 pregnancies (24.9/1000 users), according to the high-specificity definition. Of these, 1331 (90.4%) terminated spontaneously or were terminated by medical intervention. Among the 118 live births were 11 (9.3%) cases of congenital malformation. Pregnancy rates during isotretinoin treatment remained constant between 1996 and 2011. INTERPRETATION: Adherence to the isotretinoin pregnancy prevention program in Canada was poor during the 15-year period of this study.

Head to head comparison of the propensity score and the high-dimensional propensity score matching methods.

BACKGROUND: Comparative performance of the traditional propensity score (PS) and high-dimensional propensity score (hdPS) methods in the adjustment for confounding by indication remains unclear. We aimed to identify which method provided the best adjustment for confounding by indication within the context of the risk of diabetes among patients exposed to moderate versus high potency statins. METHOD: A cohort of diabetes-free incident statins users was identified from the Quebec's publicly funded medico-administrative database (Full Cohort). We created two matched sub-cohorts by matching one patient initiated on a lower potency to one patient initiated on a high potency either on patients' PS or hdPS. Both methods' performance were compared by means of the absolute standardized differences (ASDD) regarding relevant characteristics and by means of the obtained measures of association. RESULTS: Eight out of the 18 examined characteristics were shown to be unbalanced within the Full Cohort. Although matching on either method achieved balance within all examined characteristic, matching on patients' hdPS created the most balanced sub-cohort. Measures of associations and confidence intervals obtained within the two matched sub-cohorts overlapped. CONCLUSION: Although ASDD suggest better matching with hdPS than with PS, measures of association were almost identical when adjusted for either method. Use of the hdPS method in adjusting for confounding by indication within future studies should be recommended due to its ability to identify confounding variables which may be unknown to the investigators.

Seasonal effects on the occurrence of nocturnal leg cramps: a prospective cohort study.

BACKGROUND: It has been anecdotally reported that nocturnal leg cramps in pregnant women are worse in summer. We analyzed population-level data to determine whether the symptom burden of nocturnal leg cramps is seasonal in the general population. METHODS: We examined time-series data for 2 independent measures of the symptom burden of leg cramps: (a) new quinine prescriptions (reflecting new or escalating treatment of leg cramps) from December 2001 to October 2007 among adults aged 50 years and older, which were obtained from linked health care databases that contain the prescribing information for the 4.2 million residents of British Columbia, Canada; and (b) the Internet search volume from February 2004 to March 2012 for the term "leg cramps" (reflecting public interest), which we obtained from Google Trends data and geographically limited to the United States and Australia. We assessed seasonality by determining how well a least-squares sinusoidal model predicted variability in the outcomes. RESULTS: New quinine prescriptions and Internet searches related to leg cramps were both seasonal, with highs in mid-summer and lows in mid-winter, and a peak-to-peak variability that was about two-thirds of the mean. Seasonality accounted for 88% of the observed monthly variability in new quinine prescriptions (p < 0.001) and 70% of the observed variability in Internet searches related to leg cramps (p < 0.001). INTERPRETATION: New quinine prescriptions and Internet searches related to leg cramps were seasonal and roughly doubled between the winter lows and summer highs. Why a disorder of peripheral motor neurons displays such strong seasonality warrants exploration.

Proton pump inhibitors and the risk of hospitalisation for community-acquired pneumonia: replicated cohort studies with meta-analysis.

OBJECTIVE: Previous observational studies suggest that the use of proton pump inhibitors (PPIs) may increase the risk of hospitalisation for community-acquired pneumonia (HCAP). However, the potential presence of confounding and protopathic biases limits the conclusions that can be drawn from these studies. Our objective was, therefore, to examine the risk of HCAP with PPIs prescribed prophylactically in new users of non-steroidal anti-inflammatory drugs (NSAIDs). DESIGN: We formed eight restricted cohorts of new users of NSAIDs, aged ≥40 years, using a common protocol in eight databases (Alberta, Saskatchewan, Manitoba, Ontario, Quebec, Nova Scotia, US MarketScan and the UK's General Practice Research Database (GPRD)). This specific patient population was studied to minimise bias due to unmeasured confounders. High-dimensional propensity scores were used to estimate site-specific adjusted ORs (aORs) for HCAP at 6 months in PPI patients compared with unexposed patients. Fixed-effects meta-analytic models were used to estimate overall effects across databases. RESULTS: Of the 4,238,504 new users of NSAIDs, 2.3% also started a PPI. The cumulative 6-month incidence of HCAP was 0.17% among patients prescribed PPIs and 0.12% in unexposed patients. After adjustment, PPIs were not associated with an increased risk of HCAP (aOR=1.05; 95% CI 0.89 to 1.25). Histamine-2 receptor antagonists yielded similar results (aOR=0.95, 95% CI 0.75 to 1.21). CONCLUSIONS: Our study does not support the proposition of a pharmacological effect of gastric acid suppressors on the risk of HCAP.