A cross-sectional study of shift work, sleep quality and cardiometabolic risk in female hospital employees.

OBJECTIVES: Investigating the potential pathways linking shift work and cardiovascular diseases (CVD), this study aimed to identify whether sleep disturbances mediate the relationship between shift work and the metabolic syndrome, a cluster of CVD risk factors. DESIGN: Cross-sectional study. SETTING: A tertiary-level, acute care teaching hospital in Southeastern Ontario, Canada. PARTICIPANTS: Female hospital employees working a shift schedule of two 12 h days, two 12 h nights, followed by 5 days off (n=121) were compared with female day-only workers (n=150). PRIMARY AND SECONDARY OUTCOME MEASURES: Each of the seven components of the Pittsburgh Sleep Quality Index (PSQI) was measured. Of these, PSQI global score, sleep latency and sleep efficiency were examined as potential mediators in the relationship between shift work and the metabolic syndrome. RESULTS: Shift work status was associated with poor (>5) PSQI global score (OR=2.10, 95% CI 1.20 to 3.65), poor (≥2) sleep latency (OR=2.18, 95% CI 1.23 to 3.87) and poor (≥2) sleep efficiency (OR=2.11, 95% CI 1.16 to 3.84). Although shift work was associated with the metabolic syndrome (OR=2.29, 95% CI 1.12 to 4.70), the measured components of sleep quality did not mediate the relationship between shift work and the metabolic syndrome. CONCLUSIONS: Women working in a rapid forward rotating shift pattern have poorer sleep quality according to self-reported indicators of the validated PSQI and they have a higher prevalence of the metabolic syndrome compared with women who work during the day only. However, sleep quality did not mediate the relationship between shift work and the metabolic syndrome, suggesting that there are other psychophysiological pathways linking shift work to increased risk for CVD.

Hypotheses for mechanisms linking shiftwork and cancer.

Shift work has been associated with various adverse health outcomes. In particular, there has been a recent flourish in investigating potential cancer risk associated with working night shifts and other shift schedules. Epidemiologic studies have revealed generally weak associations due to several methodological challenges such as lack of standard classifications of shift or night work. The field also has been hindered by a lack of clarity about the possible mechanisms by which shiftwork could have an effect on cancer risk. One possible mechanism is reduced production of melatonin caused by exposure to light at night. Although there is a growing body of evidence that provides some support for this mechanism, several other mechanisms also make sense from a biological point of view. Further, the relatively weak magnitude of the associations between light at night and melatonin level suggests that multiple factors may be operating along the pathway between shift work and adverse health consequences (including cancer risk). Here we propose four additional mechanisms that should be considered for a comprehensive investigation of these potential pathways. These are: phase shift; sleep disruption; lifestyle factors (such as poor quality diets, less physical activity and higher BMI); and lower vitamin D. Consideration of all these mechanisms is necessary in order to design effective preventative workplace strategies. In developed countries, approximately 20% of the population undertake shiftwork and, while we are unlikely to be able to eliminate shiftwork from current work practices, there are aspects of shiftwork that can be modified and there may be facets of individual susceptibility that we may be able to identify and target for prevention.

A population-based case-control study of Selective Serotonin Reuptake Inhibitors (SSRIs) and breast cancer: the impact of duration of use, cumulative dose and latency.

BACKGROUND: Selective serotonin reuptake inhibitors (SSRIs), a popular class of antidepressants, may increase breast cancer risk by stimulating the secretion of prolactin, a potential tumour promoter. We evaluated the effects of duration of SSRI use, cumulative dose, and latency on the risk of breast cancer by conducting a population-based case-control study utilizing Saskatchewan health databases. METHODS: Cases included 1,701 women with primary invasive breast cancer diagnosed from 2003 to 2006, and controls consisted of 17,017 women, randomly selected from the population registry. Use of SSRIs was compiled using the Saskatchewan prescription database. Unconditional logistic regression was conducted to evaluate the impact of duration of combined SSRI use (total number of prescriptions dispensed), cumulative dose (total dosage received) and timing of use (two or more years, two to seven years and more than seven years prior to index date) on the risk of breast cancer. RESULTS: Overall, SSRI use was not associated with an increased risk of breast cancer regardless of our definition of cumulative use (total number of prescriptions dispensed and total dosage). In addition, our results indicate that prolonged SSRI use does not have a latent effect on breast cancer risk. Also, our findings are not suggestive of an increased risk of breast cancer with the use of individual SSRIs. CONCLUSIONS: Our study improved upon most previous studies by having a longer follow-up period, a larger sample size of long-term SSRI users and consideration of risk during specific exposure time windows that take latency into account. Given the potential health benefits of using SSRIs, our results suggest that the issue of breast cancer risk may no longer be a concern for women requiring long-term SSRIs.

A systematic review of several potential non-genetic risk factors for multiple sclerosis.

We reviewed the literature published in the English language to determine the weight of evidence for several potential non-genetic risk factors for multiple sclerosis, including solar ultraviolet radiation (UVR), sex hormones and dietary fat/fatty acids. We ranked the plausibility of each factor and graded the methodological rigour of case-control and cohort studies to determine whether there was a sufficient number of high-quality studies to weigh the evidence. Based on our criteria, the plausibility for solar UVR and sex hormones is good and fair for dietary fat/fatty acids. However, the body of epidemiologic evidence is insufficient for these three sets of risk factors. We did not find a sufficient number of methodologically rigorous studies to weigh the evidence for any of the potential risk factors we examined.

Oncogenic human papillomavirus infection and cervical lesions in aboriginal women of Nunavut, Canada.

BACKGROUND: The high rate of cervical cancer among aboriginal women of northern Canada has prompted the search for more aggressive methods to augment Papanicolaou (Pap) screening in this population. Nearly all cervical cancers result from oncogenic human papillomavirus (HPV) infections. This has generated interest for incorporating HPV testing into the current screening program. GOALS: To determine the prevalence of oncogenic HPVs in Nunavut, and to assess the association between HPV and squamous intraepithelial lesions (SIL). STUDY DESIGN: A cross-sectional study was conducted on the Pap-screened populations in 19 communities of Nunavut, Canada. Liquid-based cytology was used to screen for SIL. HPV testing was performed using the Hybrid Capture II assay. Correlates of HPV infection and SIL were assessed by logistic regression with control for potential confounders. RESULTS: In 1290 women ages 13 to 79 years, the prevalence rate was 26% for oncogenic HPV and 6.9% for SIL. The odds ratio for the association between HPV and SIL was 37.9 (95% CI, 17.7-80.8) after multivariate adjustment. This association increased markedly with increasing viral load. More than 90% of the women with squamous intraepithelial lesions had positive test results for HPV. More than 75% of the women who had positive test results for HPV but negative test results for SIL were younger than 30 years. CONCLUSION: The results of this study form the basis for further evaluation of the role that liquid-based cytology and HPV testing plays and will contribute to the strategy for cervical cancer prevention in Nunavut.

Organochlorines and breast cancer risk by receptor status, tumor size, and grade (Canada).

OBJECTIVE: We evaluated the association between organochlorines and breast cancer subtype defined by the tumor characteristics: estrogen receptor status, progesterone receptor status, tumor size, and grade. METHODS: A case-control study was conducted from 1995 to 1997 in Kingston and Toronto, Canada. Breast adipose tissue, taken from 217 cases and 213 biopsy controls frequency-matched on age, was analysed for 14 polychlorinated biphenyl (PCB) congeners and 10 pesticides. RESULTS: Adjusting for age, geometric means of several organochlorines differed by estrogen receptor status and tumor grade (p < 0.05). Odds ratios (ORs) for each organochlorine relative to the common control group for breast cancers of differing subtype were compared using polytomous logistic regression. Although the ORs did not differ significantly by subtype, the ORs of PCBs and p, p'-1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) were higher with risk of estrogen receptor-negative breast cancer than estrogen receptor-positive breast cancer. One of the most extreme differences was with DDE, where the OR for the association with risk of estrogen receptor-negative breast cancer was 2.4 (95% confidence interval (CI) 1.0-5.4) in the uppermost tertile relative to the lowest, whereas the corresponding OR for risk of estrogen receptor-positive breast cancer was 1.1 (95% CI 0.6-1.9). PCBs also tended to be more strongly positively associated with risk of larger and higher-grade tumors. CONCLUSIONS: The association between organochlorines and breast cancer risk did not significantly differ by subtype, but many PCBs were more strongly associated with tumors of poor prognosis.

Feeling your body or feeling badly: evidence for the limited validity of the Somatosensory Amplification Scale as an index of somatic sensitivity.

OBJECTIVE: The Somatosensory Amplification Scale (SSAS) purports to measure the extent to which individuals are sensitive to their bodies. The present study examined the psychometric properties of the SSAS in two studies with university students. METHODS: Participants completed the SSAS, various cross-sectional measures of somatic and psychological distress, longitudinal measures of somatic symptoms, daily hassles and mood, and participated in a heartbeat detection task (Study 2 only). RESULTS: The SSAS was correlated with cross-sectional measures of somatic symptom reporting, but not with somatic symptoms reported on a daily basis nor with an index of interoceptive sensitivity. The SSAS was also correlated with several indices of general distress including anxious and depressive symptoms, daily hassles, and negative emotionality. CONCLUSION: Taken together, the results suggest that the SSAS is more likely an index of negative emotionality and general distress than a valid measure of somatic sensitivity per se.

Cancer mortality among males in relation to exposures assessed through a job-exposure matrix.

To identify potential associations between workplace exposures and cancer mortality risks, job titles collected from 1965 to 1971 for 58,678 men (a subset of a large representative sample of the Canadian workforce) were transformed into probable chemical exposures using a job-exposure matrix developed in Montreal. Mortality follow-up was determined through computerized record linkage with the National Mortality Database in Canada for 1965-1991. Cancer mortality risk was evaluated at two levels of exposure, any and substantial, using Poisson regression controlling for age, calendar period, and social class. Among the 58,678 men, 3,160 died of cancer. Using a liberal reporting criterion, relative risk (RR) >1.0, five or more exposed cancer deaths, p < or = 0.100, several potential associations were identified, including: lung cancer and any exposure to abrasives dust (RR = 2.84), prostate cancer and any exposure to calcium carbonate (RR = 2.46), and prostate cancer and substantial exposure to metallic dust (RR = 2.13).

Breast adipose tissue concentrations of polychlorinated biphenyls and other organochlorines and breast cancer risk.

Numerous studies have examined the relationship between organochlorines and breast cancer, but the results are not consistent. In most studies, organochlorines were measured in serum, but levels in breast adipose tissue are higher and represent cumulative internal exposure at the target site for breast cancer. Therefore, a hospital-based case-control study was conducted in Ontario, Canada to evaluate the association between breast cancer risk and breast adipose tissue concentrations of several organochlorines. Women scheduled for excision biopsy of the breast were enrolled and completed a questionnaire. The biopsy tissue of 217 cases and 213 benign controls frequency matched by study site and age in 5-year groups was analyzed for 14 polychlorinated biphenyl (PCB) congeners, total PCBs, and 10 other organochlorines, including p,p'-1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene. Multiple logistic regression was used to assess the magnitude of risk. While adjusting for age, menopausal status, and other factors, odds ratios (ORs) were above 1.0 for almost all organochlorines except five pesticide residues. The ORs were above two in the highest concentration categories of PCB congeners 105 and 118, and the ORs for these PCBs increased linearly across categories (Ps for trend < or =0.01). Differences by menopausal status are noted especially for PCBs 105 and 118, with risks higher among premenopausal women, and for PCBs 170 and 180, with risks higher among postmenopausal women. Clear associations with breast cancer risk were demonstrated in this study for some PCBs measured in breast adipose tissue.

Surveillance of potential associations between occupations and causes of death in Canada, 1965-91.

OBJECTIVE: To detect unsuspected associations between workplace situations and specific causes of death in Canada. METHODS: An occupational surveillance system was established consisting of a cohort of 457,224 men and 242,196 women employed between 1965 and 1971, constituting about 10% of the labour force in Canada at that time. Mortality between 1965 and 1991 has been determined by computerised record linkage with the Canadian mortality database. Through regression analysis, associations between 670 occupations and 70 specific causes of death were measured. RESULTS: There were almost 116,000 deaths among men and over 26,800 deaths among women. About 28,000 comparisons were made between occupations and specific causes of death. With various reporting criteria, several potential associations were highlighted, including: infectious disease mortality among barbers and hairdressers; laryngeal cancer among male metal fitters and assemblers; lung cancer among female waiters; breast cancer among female metal fitters and assemblers; brain cancer among female nursing assistants and male painters; and ischaemic heart disease among female inspectors and foremen and among male taxi drivers and chauffeurs. CONCLUSIONS: When excess risk of mortality is apparent, the intention of this occupational surveillance system is to spark further studies to gain aetiological knowledge.

Improved disease reporting: a randomized trial of physicians.

OBJECTIVES: To determine if a heightened, passive surveillance system increases the number of physicians reporting two notifiable diseases during a six-month period. METHODS: We conducted a randomized trail among 145 community-based primary care physicians in two counties in Eastern Ontario. Intervention group physicians received a three-part intervention aimed at improving their communication with the health unit to whom all physicians are mandated to report notifiable diseases. The control group physicians remained part of the usual disease reporting system. The outcome was assessed by a relative risk comparing the number of physicians reporting among the intervention group to that in the control group. RESULTS: Seventy physicians received the intervention and 75 physicians were in the control group. The relative risk for the number of physicians reporting at least one case was 5.9 (95% CI 2.6-13.2). CONCLUSIONS: The intervention had an impact on reporting of notifiable diseases by physicians.

Breast cancer and organochlorines: a marker for susceptibility?

The incidence of breast cancer is increasing and despite extensive research efforts, the etiology of this disease is largely unknown. Most women exhibit no known risk factors except for their age and sex. It has recently been postulated that the increased breast cancer incidence might be attributed to exposure to environmental carcinogens such as the organochlorine compounds. In this article, the scientific literature with respect to this possibility is reviewed and alternative hypotheses, which may in part explain the possible role of organochlorine compounds in the etiology of breast cancer, are presented.

The relationship between dietary fat intake and risk of colorectal cancer: evidence from the combined analysis of 13 case-control studies.

The objective of this study was to examine the effects of the intake of dietary fat upon colorectal cancer risk in a combined analysis of data from 13 case-control studies previously conducted in populations with differing colorectal cancer rates and dietary practices. Original data records for 5,287 cases of colorectal cancer and 10,470 controls were combined. Logistic regression analysis was used to estimate odds ratios (OR) for intakes of total energy, total fat and its components, and cholesterol. Positive associations with energy intake were observed for 11 of the 13 studies. However, there was little, if any, evidence of any energy-independent effect of either total fat with ORs of 1.00, 0.95, 1.01, 1.02, and 0.92 for quintiles of residuals of total fat intake (P trend = 0.67) or for saturated fat with ORs of 1.00, 1.08, 1.06, 1.21, and 1.06 (P trend = 0.39). The analysis suggests that, among these case-control studies, there is no energy-independent association between dietary fat intake and risk of colorectal cancer. It also suggests that simple substitution of fat by other sources of calories is unlikely to reduce meaningfully the risk of colorectal cancer.

Quality of life among persons with multiple sclerosis and their caregivers.

For those with a chronic illness, suffering may result not only from physical limitations, but also from the psychosocial consequences of having a chronic condition. Few studies have described the psychosocial characteristics of the physically disabled. Even more rare are population-based studies of quality of life (QOL) among persons with multiple sclerosis (MS) and their caregivers. We conducted a large survey of persons with MS and their caregivers in Ontario using self-completed mailed questionnaires. The objectives included describing satisfaction with QOL and determining relationships between QOL as a whole and several other factors, such as demographic characteristics and measures of physical disability. Response rates were 83% for those with MS and 72% for their caregivers. Based on 697 respondents with MS, mean age was 48 years, 70% were women, and 75% were married. While 24% experienced no mobility restrictions, the majority required some type of aid or a wheelchair for getting around. Health received the lowest satisfaction rating among the six components of QOL, while finances received a relatively low satisfaction rating from the 345 caregivers. Less satisfaction with several QOL components was evident for those with MS compared with the disabled in the Canadian general population, and for caregivers compared with the able-bodied general population. Poorer QOL as a whole among those with MS was associated with unemployment, MS symptoms of moderate or worse, fatigue, mobility limitations on stairs, a disease course other than stable, and was most strongly related to interference by MS in social activities. Among caregivers, poorer QOL as a whole was associated with being a spouse, longer duration of caregiving, moderate or worse MS symptoms in the care recipient, and most strongly related to a care recipient's current MS disease course of other than stable. Through an understanding of the satisfaction with QOL of persons with MS and caregivers, and the relationships with other important factors, autonomy and home care may be supported and prolonged, while preventing unnecessary institutionalization.

The efficacy of nonopioid analgesics for postoperative dental pain: a meta-analysis.

The evidence for the efficacy of nonopioid analgesics in the dental pain model was examined by conducting a meta-analysis. Studies were obtained by searching the literature from August 1996 back to 1975 using the terms pain, analgesics, and dentistry. This led to the review of 294 articles, of which 33 studies met the inclusion criteria. Pain scale results were transformed into a common percent scale and converted to N-weighted means with differences in efficacy considered significant using a 95% confidence interval. Collectively, therapeutic doses of the nonsteroidal anti-inflammatory drugs (NSAIDs) commonly used in dentistry were significantly more efficacious than the combination of acetaminophen (600 or 650 mg) with codeine (60 mg). Similarly, specific doses of each of diflunisal, flurbiprofen, ibuprofen, and ketorolac were significantly more efficacious than the commonly used acetaminophen-codeine combination. These quantitative results show that particular NSAIDs may be more efficacious than the acetaminophen-codeine combination for relief of postoperative dental pain.

Assistance arrangements and use of services among persons with multiple sclerosis and their caregivers.

A large population-based survey of persons with multiple sclerosis (MS) and their caregivers was conducted in Ontario using self-completed mailed questionnaires. The objectives included describing assistance arrangements, needs, and use of and satisfaction with services, and comparing perceptions of persons with MS and their caregivers. Response rates were 83% and 72% for those with MS and caregivers, respectively. Based on 697 respondents with MS whose mean age is 48 years, 70% are female, and 75% are married. While 24% experience no mobility restrictions, the majority require some type of aid or a wheelchair for getting around. Among 345 caregivers, who have been providing care for 9 years on average, the majority are spouses. Caregivers report providing more frequent care than do persons with MS report receiving it, particularly for the following activities of daily living: eating, meal preparation, and help with personal finances. Caregivers also report assistance of longer duration per day than do care recipients with MS. Frequency and duration of assistance are positively associated with increased MS symptom severity and reduced mobility. Generally there is no rural-urban disparity in service provision, utilization or satisfaction, and although there is a wide range of service utilization, satisfaction is consistently high. Respite care is rarely used by caregivers. Use of several services is positively associated with increased severity of MS symptoms and reduced mobility. Assistance arrangements and use of services, each from the point of view of persons with MS and their caregivers, must be taken into account in efforts to prolong home care and to postpone early institutionalization of persons with MS.

Congenital anomalies among the offspring of fire fighters.

A case-control study has been conducted to determine the association between employment as a fire fighter and congenital heart defects among the offspring. Cases were fathers of all children born between 1979 and 1986 in Ontario, Canada, who were diagnosed with a cardiac congenital anomaly during the first year of life (n = 9340). Matched controls (n = 9340), defined as fathers whose child did not have a congenital anomaly, were randomly selected from the Ontario birth certificate file. In order to identify those fathers who had been employed as a fire fighter, the cases and controls were linked to a cohort of Metropolitan Toronto fire fighters. Eleven cases and nine controls worked as fire fighters, giving an odds ratio of 1.22 (95 percent confidence interval 0.46-3.33). This study had sufficient power to detect the level of risk reported in one previous study; however, these results do not support a hypothesis of elevated risk of cardiac congenital anomalies among the offspring of fire fighters.

Occupational risk factors for prostate cancer: results from a case-control study in Montréal, Québec, Canada.

A population-based case-control study of cancer and occupation was carried out in Montréal, Canada. Between 1979 and 1986, 449 pathologically confirmed cases of prostate cancer were interviewed, as well as 1,550 cancer controls and 533 population controls. Job histories were evaluated by a team of chemist/hygienists using a checklist of 294 workplace chemicals. After preliminary evaluation, 17 occupations, 11 industries, and 27 substances were selected for multivariate logistic regression analyses to estimate the odds ratio between each occupational circumstance and prostate cancer with control for potential confounders. There was moderate support for risk due to the following occupations: electrical power workers, water transport workers, aircraft fabricators, metal product fabricators, structural metal erectors, and railway transport workers. The following substances exhibited moderately strong associations: metallic dust, liquid fuel combustion products, lubricating oils and greases, and polyaromatic hydrocarbons from coal. While the population attributable risk, estimated at between 12% and 21% for these occupational exposures, may be an overestimate due to our method of analysis, even if the true attributable fraction were in the range of 5-10%, this represents an important public health issue.

Smokers are unaware of the filter vents now on most cigarettes: results of a national survey.

OBJECTIVE: To evaluate awareness and knowledge of cigarette filter ventilation in a national probability sample of smokers of Ultra-light, Light, and regular cigarettes. DESIGN: Random-digit-dialling and computer-assisted telephone interviewing was used on a probability sample of daily cigarette smokers (ages 18 and above). SUBJECTS AND SETTING: 218 Smokers of Ultra-light cigarettes, 360 smokers of Light cigarettes, and 210 smokers of Regular cigarettes living in the continental United States. MAIN OUTCOME MEASURES: Percentage of respondents indicating knowledge of the presence of filter vents and the consequences of behavioural blocking of vents. RESULTS: Many smokers had not heard about or seen the filter holes: 43% (95% CI = 36 to 50%) of smokers of Ultra-lights, 39% (95% CI = 34 to 44%) of smokers of Lights, and 47% (95% CI = 40 to 54%) of smokers of Regulars. About two in three smokers either did not know of the existence of rings of small holes on the filters of some cigarettes, or did not know that blocking increases tar yields: 69% (95% CI = 63 to 75%) of Ultra-lights, 66% (95% CI = 61 to 71%) of Lights, and 69% (95% CI = 63 to 75%) of Regulars. CONCLUSIONS: Smokers are generally unaware of the presence and function of filter vents-a major design feature subject to behavioural blocking by smokers and now present on most cigarettes in the United States. Smokers and policy-makers need to be informed about the presence of filter vents and how vent blocking increases tar and nicotine yields from ostensibly very low-yield cigarettes.