Social inequalities in the provision of obstetric services in Norway 1967-2009: a population-based cohort study.

BACKGROUND: Socioeconomic (SE) inequalities have been observed in a number of adverse outcomes of pregnancy and many of the risk factors for such outcomes are associated with a low SE level. However, SE inequalities persist even after adjustment for these risk factors. Less well-off women are more vulnerable, but may also get less adequate health services. The objective of the present study was to assess possible associations between SE conditions in terms of maternal education as well as ethnic background and obstetric care. METHODS: A population-based national cohort study from the Medical Birth Registry of Norway. The study population comprised 2 305 780 births from the observation period 1967-2009. Multilevel analysis was used because of the hierarchical structure of the data. Outcome variables included induction of labour, epidural analgesia, caesarean section, neonatal intensive care and perinatal death. RESULTS: While medical interventions in the 1970s were employed less frequently in women of short education and non-western immigrants, this difference was eliminated or even reversed towards the end of the observation period. However, an excess perinatal mortality in both the short-educated [adjusted relative risk (aRR) = 2.49] and the non-western immigrant groups (aRR = 1.75) remained and may indicate increasing health problems in these groups. CONCLUSION: Even though our study suggests a fair and favourable development during the last decades in the distribution across SE groups of obstetric health services, the results suggest that the needs for obstetric care have increased in vulnerable groups, requiring a closer follow-up.

Maternal Smoking Status in Successive Pregnancies and Risk of Having a Small for Gestational Age Infant.

BACKGROUND: Smoking during pregnancy is linked to having a small for gestational age (SGA) baby. We estimated SGA risk among women who smoked persistently, quit smoking or started smoking during their first two pregnancies. METHODS: Data from the population-based Medical Birth Registry of Norway was used to evaluate self-reported smoking at the beginning and end of two successive pregnancies among 118 355 Nordic women giving birth 1999-2014. Relative risks (RR) with 95% confidence intervals (CI) of SGA in the second pregnancy were estimated using adjusted generalised linear models with non-smokers during both pregnancies serving as referent category. RESULTS: Daily smokers throughout both pregnancies had almost threefold increased SGA risk in the second pregnancy (RR 2.9, 95% CI 2.7, 3.1). Daily smokers in the first pregnancy, who abstained in the second, had a 1.3-fold increased risk (95% CI 1.1, 1.5). Intermediate risks were found among persistent daily smokers who quit by the end of the second pregnancy (RR 2.0, 95% CI 1.6, 2.4) and non-smokers in first pregnancy who smoked daily throughout their second (RR 1.8, 95% CI 1.4, 2.3). Persistently smoking women without SGA in first pregnancy, had a 2.7-fold increased risk of SGA in second pregnancy (95% CI 2.5, 3.0). CONCLUSIONS: Smoking throughout two successive pregnancies was associated with the greatest increased SGA risk compared with non-smokers, while cessation before or during the second pregnancy reduced this risk. Women who smoked in the first pregnancy without experiencing SGA are not protected against SGA in second pregnancy if they continue smoking.

Quality indicators for the referral process from primary to specialised mental health care: an explorative study in accordance with the RAND appropriateness method.

BACKGROUND: Communication between involved parties is essential to ensure coordinated and safe health care delivery. However, existing literature reveals that the information relayed in the referral process is seen as insufficient by the receivers. It is unknown how this insufficiency affects the quality of care, and valid performance measures to explore it are lacking. The aim of the present study was to develop quality indicators to detect the impact that the quality of referral letters from primary care to specialised mental health care has on the quality of mental health services. METHODS: Using a modified version of the RAND/UCLA appropriateness method, a systematic literature review and focus group interviews were conducted to define quality indicators for mental health care expected to be affected by the quality of referral information. Focus group participants included psychiatrists, psychologists, general practitioners, patient representatives and managers. The existing evidence and suggested indicators were presented to expert panels, who assessed the indicators by their validity, reliability, sensitivity and feasibility. RESULTS: Sixteen preliminary indicators emerged during the focus group interviews and literature review. The expert panels recommended four of the 16 indicators. The recommended indicators measure a) timely access, b) delay in the process of assessing the referral, c) delay in the onset of care and d) the appropriateness of the referral. Adjustment was necessary for five other indicators, and seven indicators were rejected because of expected confounding factors reducing their validity and sensitivity. CONCLUSIONS: The quality of information relayed in the referral process from primary care to specialised mental health care is expected to affect a wide range of dimensions defining high quality care. The expected importance of the referral process for ensuring 'timely access'-one of the six aims of high-quality health care defined by the Institute of Medicine-is highlighted. Exploring the underlying mechanisms for the potential impact of referral information on patient outcomes is recommended to enhance quality of care. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01374035 (28 April 2011).

Socio-economic risk factors for preterm birth in Norway 1999-2009.

AIMS: Preterm birth is a major cause of perinatal mortality and morbidity and is strongly associated with socio-economic factors. The objective of this study was to examine the associations of maternal education, marital status and ethnicity with preterm birth and to determine the extent to which such associations can be explained by the established risk factors of maternal age, parity and smoking. METHODS: This was a register-based cohort study with data from the Medical Birth Registry of Norway 1999-2009 and Statistics Norway. The sample included all singleton spontaneous births in Norway from 1999 to 2009 (n=494,073). The main outcome measure was preterm birth (gestational age <37 weeks). RESULTS: Low maternal education and single motherhood were associated with preterm birth. After adjustment for the established risk factors, the excess risks were reduced, but remained statistically significant. The relative risk for low education was reduced from 1.50 to 1.36 and for single motherhood from 1.50 to 1.28. Women from Asia had a higher risk of preterm birth than Norwegian-born women (relative risk 1.29) with minor effects of adjustment. CONCLUSIONS SEVERAL SOCIO-ECONOMIC RISK FACTORS ARE ASSOCIATED WITH PRETERM BIRTH IN NORWAY IN ADDITION TO THE ESTABLISHED RISK FACTORS, PRENATAL HEALTH CARE SHOULD FOCUS ON HIGH-RISK GROUPS DEFINED BY MATERNAL EDUCATION, MARITAL STATUS AND ETHNICITY.

Can 'early programming' be partly explained by smoking? Results from a prospective, population-based cohort study.

BACKGROUND: Numerous studies have focused the association between low birthweight and later disease. Our objective was to study the association between birthweight and later adult smoking and thereby explore a possible mechanism for the association between low birthweight and later adult disease. METHODS: We studied associations between birthweight of women (n=247704) born in 1967-1995 and smoking habits at the end of their pregnancy 13-42 years later in a prospective, population-based cohort study from The Medical Birth Registry of Norway. Similarly, the association between birthweight of men (n=194393) and smoking habits of their partners were assessed. Finally, we studied the relation between smoking habits of the participating women and the cause specific death of their mothers (n=222808). RESULTS: Twenty per cent of women with birthweight less than 2000 g were adult daily smokers compared with 11% with birthweight 4000-4499 g [relative risk=1.8, 95% confidence interval 1.4, 2.2]. Similarly, we found an association between men's birthweight and their partners smoking habits. Mothers of smoking women had doubled risk of dying from lung cancer and from cardiovascular disease compared with mothers of non-smoking women. CONCLUSIONS: Being born with low birthweight is associated with smoking in adulthood. Associations of adult smoking with partners' birthweight and mothers' smoking-related causes of death suggest a shared smoking environment, and may account for some of the established association between birthweight and later cardiovascular disease.

Symptom trajectories of post-COVID sequelae in patients with acute Delta or Omicron infection in Bergen, Norway.

Introduction: A substantial proportion of the over 700 million COVID-19 cases world-wide experience long-term symptoms. The objectives of this study were to compare symptom trajectories and risk factors for post-COVID-19 condition after Delta and Omicron infection. Methods: This study consecutively recruited patients with SARS-CoV-2 infection from November 2021 to March 2022. We recorded demographics, comorbidities, vaccination status, sick leave, and 18 symptoms during acute infection and after 4 months. The primary outcome measures were symptoms during acute infection and after 4 months. Secondary outcome measures were work and school absenteeism. Results: We followed a cohort of 1,374 non-hospitalized COVID-19 patients in Bergen, Norway, at three time points. The median age was 39.8 years and 11% were children <16 years. Common acute upper respiratory symptoms waned during follow-up. Fatigue remained common from acute infection (40%) until after 4 months (37%). Four months post-infection, patients reported increased frequencies of dyspnea (from 15% during acute illness to 25% at 4 months, p < 0.001), cognitive symptoms (from 9 to 32%, p < 0.001) and depression (from 1 to 17%, p < 0.001). Patients infected with Omicron reported less dyspnea (22% versus 27%, p = 0.046) and smell/taste problems (5% versus 19%, p < 0.001) at 4 months follow-up than those with Delta infection. Comorbidities and female sex were risk factors for persistent dyspnea and cognitive symptoms. Ten percent reported sick leave after acute illness, and vaccination reduced the risk of absenteeism (adjusted risk ratio: 0.36, 95% confidence interval: 0.15, 0.72, p = 0.008). Conclusion: At 4 months, home-isolated patients infected with Omicron reported overall comparable symptom burden, but less dyspnea and smell/taste problems than Delta infected patients. Several acute symptoms waned during follow-up. It is worrying that dyspnea, neurocognitive symptoms, and particularly depression, increased significantly during the first 4 months after acute infection. Previous vaccination was protective against prolonged sick leave.

Patient experiences with interventions to reduce surgery cancellations: a qualitative study.

BACKGROUND: The cancellation of planned surgery harms patients, increases waiting times and wastes scarce health resources. Previous studies have evaluated interventions to reduce cancellations from medical and management perspectives; these have focused on cost, length of stay, improved efficiency, and reduced post-operative complications. In our case a hospital had experienced high cancellation rates and therefore redesigned their pathway for elective surgery to reduce cancelations. We studied how patients experienced interventions to reduce cancellations. METHODS: We conducted a comparative, qualitative case study by interviewing 8 patients who had experienced the redesigned pathway, and 8 patients who had experienced the original pathway. We performed a content analysis of the interviews using a theory-based coding scheme. Through a process of coding and condensing, we identified themes of patient experience. RESULTS: We identified three common themes summarizing patients' positive experiences with the effects of the interventions: the importance of being involved in scheduling time for surgery, individualized preparation before the hospital admission, and relationships with few clinicians during their hospital stay. CONCLUSIONS: Patients appreciated the effects of interventions to reduce cancellations, because they increased their autonomy. Unanticipated consequences were that the telephone reminder created a personalized dialogue and centralization of surgical preparation and discharge processes improved continuity of care. Thus apart from improving surgical logistics, the pathway became more patient-centered.

Self-reported smoking status and plasma cotinine concentrations among pregnant women in the Norwegian Mother and Child Cohort Study.

INTRODUCTION: Underreporting of smoking in epidemiologic studies is common and may constitute a validity problem, leading to biased association measures. In this prospective study, we validated self-reported tobacco use against nicotine exposure assessed by plasma cotinine in the Norwegian Mother and Child Cohort Study (MoBa). METHODS: The study was based on a subsample of 2,997 women in the MoBa study who delivered infants during the period 2002-2003. Self-reported tobacco use (test variable) and plasma cotinine concentrations (gold standard) were assessed at approximately gestational week 18. RESULTS: Daily smoking was reported by 9% of the women, occasional smoking by 4%, and nonsmoking by 86% of the women. Sensitivity and specificity for self-reported smoking status were calculated using a cotinine cut-off estimated from the study population (30 nmol/l). Plasma cotinine concentrations ≥30 nmol/l were found in 94% of self-reported daily smokers, 66% of occasional smokers, and 2% of nonsmokers. After the numbers of self-reported nonsmokers with cotinine concentrations above the cut-off limit were added, the daily smoking prevalence increased from 9 to 11%. The sensitivity and specificity for self-reported daily smoking, using 30 nmol/l as the cut-off concentration, were 82 and 99%, respectively. DISCUSSION: These findings suggest that self-reported tobacco use is a valid marker for tobacco exposure in the MoBa cohort.

A biobank of primary teeth within the Norwegian Mother and Child Cohort Study (MoBa): a resource for the future.

The Norwegian Mother and Child Cohort Study (MoBa) is a prospective population-based cohort study including >100 000 pregnancies and following the children through childhood, using questionnaires and collecting biological samples. The aim of MoBa is to test specific aetiological hypotheses by estimating the association between exposure and disease, aiming at prevention. A biobank for exfoliated primary teeth collected from the children participating in MoBa has been established (MoBaTooth Biobank). Samples of tooth tissues from the primary dentition can give information about exposure to toxic and essential elements during fetal life and early infancy. Prenatally and postnatally formed tooth tissues permanently document early exposures unlike other biomarkers, as teeth form incrementally at a known rate. Results from tooth analyses will be coupled with corresponding information in the multiple questionnaires and data from analysis of other biological samples collected by MoBa. Invitations to donate one or more teeth are sent to all mothers/children in the period 2008-2016, when the child is 6.75 years old. By August 2011, 7400 participants had been recorded into the MoBaTooth database donating altogether 9798 teeth (1.3 teeth per child). The response rate was 24%, but there is a lag of >1 year in the response. Data from the tooth biobank can supply MoBa with important additional information on the uptake of trace elements during fetal life and early infancy. This information can illuminate possible causal factors of health and disease in the future.

A new pathway for elective surgery to reduce cancellation rates.

BACKGROUND: The cancellation of planned surgeries causes prolonged wait times, harm to patients, and is a waste of scarce resources. To reduce high cancellation rates in a Norwegian general hospital, the pathway for elective surgery was redesigned. The changes included earlier clinical assessment of patients, better planning and documentation systems, and increased involvement of patients in the scheduling of surgeries. This study evaluated the outcomes of this new pathway for elective surgery and explored which factors affected the outcomes. METHODS: We collected the number of planned operations, performed operations, and cancellations per month from the hospital's patient administrative system. We then used Student's t-test to analyze differences in cancellation rates (CRs) before and after interventions and a u-chart to analyze whether the improvements were sustained. We also conducted semi-structured interviews with employees of the hospital to explore the changes in the surgical pathway and the factors that facilitated these changes. RESULTS: The mean CR was reduced from 8.5% to 4.9% (95% CI for mean reduction 2.6-4.5, p < 0.001). The reduction in the CR was sustained over a period of 26 months after the interventions. The median number of operations performed per month increased by 17% (p = 0.04). A clear improvement strategy, involvement of frontline clinicians, introduction of an electronic scheduling system, and engagement of middle managers were important factors for the success of the interventions. CONCLUSION: The redesign of the old clinical pathway contributed to a sustained reduction in cancellations and an increased number of performed operations.

Sustainability of healthcare improvement: what can we learn from learning theory?

BACKGROUND: Changes that improve the quality of health care should be sustained. Falling back to old, unsatisfactory ways of working is a waste of resources and can in the worst case increase resistance to later initiatives to improve care. Quality improvement relies on changing the clinical system yet factors that influence the sustainability of quality improvements are poorly understood. Theoretical frameworks can guide further research on the sustainability of quality improvements. Theories of organizational learning have contributed to a better understanding of organizational change in other contexts. To identify factors contributing to sustainability of improvements, we use learning theory to explore a case that had displayed sustained improvement. METHODS: Førde Hospital redesigned the pathway for elective surgery and achieved sustained reduction of cancellation rates. We used a qualitative case study design informed by theory to explore factors that contributed to sustain the improvements at Førde Hospital. The model Evidence in the Learning Organization describes how organizational learning contributes to change in healthcare institutions. This model constituted the framework for data collection and analysis. We interviewed a strategic sample of 20 employees. The in-depth interviews covered themes identified through our theoretical framework. Through a process of coding and condensing, we identified common themes that were interpreted in relation to our theoretical framework. RESULTS: Clinicians and leaders shared information about their everyday work and related this knowledge to how the entire clinical pathway could be improved. In this way they developed a revised and deeper understanding of their clinical system and its interdependencies. They became increasingly aware of how different elements needed to interact to enhance the performance and how their own efforts could contribute. CONCLUSIONS: The improved understanding of the clinical system represented a change in mental models of employees that influenced how the organization changed its performance. By applying the framework of organizational learning, we learned that changes originating from a new mental model represent double-loop learning. In double-loop learning, deeper system properties are changed, and consequently changes are more likely to be sustained.

The Western Norway mental health interface study: a controlled intervention trial on referral letters between primary care and specialist mental health care.

BACKGROUND: Referral letters are the main communication means between Primary and Specialised Mental Health Care. However, studies of referral letters reveal that they lack important information, and how this lack of information affects the care for patients is unknown. This study aims to explore if and to what degree the quality of referral letters within Mental Health Care for adults can be improved and the potential improvement's impact on defined patient, professional and organisational related outcomes. METHODS AND DESIGN: A controlled study with pre and post test will be prepared and accomplished to explore the correlation between the content of referral letters and outcomes of the care for the referred patients. The study is performed in accordance with the guideline of the Medical Research Council on development and evaluation of complex interventions. Using a mixed method design, a stepwise model will be conducted: Firstly, process and outcome measures will be developed and tested. Secondly, by these measures, the results from an intervention group of General Practitioners (GPs) who receive a complex quality improvement intervention will be compared with results from a control group who perform "care as usual". Compliance to the introduced guideline will be measured as a mediator. DISCUSSION: The Western Norway Mental Health Interface Study is among the first trials to evaluate the impact of the quality of referral letters on the organization of care. This study will provide information that will be usable for healthcare managers and clinicians in both Primary and Specialised Care settings. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01374035.

In utero exposure to tobacco smoke and subsequent reduced fertility in females.

BACKGROUND: Animal studies have shown that in utero exposure to chemicals in tobacco smoke reduces female fertility, but epidemiological findings have been inconsistent. METHODS: We examined the association between in utero exposure to tobacco smoke and female fertility among women in the Norwegian Mother and Child Cohort Study, enrolled from 1999 to 2007. Around the 17th week of pregnancy, participants reported how long they took to conceive (time to pregnancy), and whether their mother smoked while pregnant with the participant. This analysis included 48 319 planned pregnancies among women aged 15-44 years. We estimated fecundability odds ratios (FORs) using a discrete-time survival analysis, adjusting for age, education and adult tobacco smoking. RESULTS: The adjusted FOR for in utero exposure to tobacco smoke among all subjects was 0.96 [95% confidence interval (CI): 0.93, 0.98], among subjects reporting no adult tobacco smoking or passive exposure it was 0.96 (95% CI: 0.93, 0.99) and among subjects reporting adult tobacco smoking or passive exposure it was 0.95 (95% CI: 0.91, 0.99). We performed a probabilistic sensitivity analysis to estimate the effect of exposure and outcome misclassification on the results, and, as expected, the association became more pronounced after taking misclassification into account. CONCLUSIONS: This large cohort study supports a small-to-modest association between in utero exposure to tobacco smoke and reduced fertility.

Young people and their GP: a register-based study of 1717 Norwegian GPs.

BACKGROUND: Internationally, there has been a call to improve the youth-friendliness of health services. In surveys, 60-90% of young people report having contact with a GP at least once a year. Regular contact with the GP can be assumed to be an indicator of a youth-friendly health service. The aim of the current study was to identify associations between a high consultation rate with young people (15-24 years) on the one hand and GP characteristics, patient list characteristics and practice profiling factors on the other. METHODS: A cross-sectional national register-based study from 2002-04 in Norwegian general practice. Data on 1717 GPs, their practice populations and a sample of 316 773 consultations with young people were used to estimate differences between GPs, using one-way analysis of variance and logistic regression. RESULTS: The mean annual consultation rate with young people was 1.4 (95% confidence interval 1.4-1.5) and 2.2 (2.1-2.2) for the age groups 15-19 and 20-24, respectively. List characteristics indicating free capacity-a shorter patient list, a growing patient list and a high access for persons not on the patient list-were associated with a high youth consultation rate. Young age of the GP, low educational level among the list population and a high rate of interdisciplinary activity by the GP were also associated with a high youth consultation rate. CONCLUSIONS: GPs seem to assign especially low priority to young people when workload is high or free capacity low. Increased awareness of these mechanisms and greater interdisciplinary cooperation could increase the youth-friendliness of general practice.

Self-selection and bias in a large prospective pregnancy cohort in Norway.

Self-selection in epidemiological studies may introduce selection bias and influence the validity of study results. To evaluate potential bias due to self-selection in a large prospective pregnancy cohort in Norway, the authors studied differences in prevalence estimates and association measures between study participants and all women giving birth in Norway. Women who agreed to participate in the Norwegian Mother and Child Cohort Study (43.5% of invited; n = 73 579) were compared with all women giving birth in Norway (n = 398 849) using data from the population-based Medical Birth Registry of Norway in 2000-2006. Bias in the prevalence of 23 exposure and outcome variables was measured as the ratio of relative frequencies, whereas bias in exposure-outcome associations of eight relationships was measured as the ratio of odds ratios. Statistically significant relative differences in prevalence estimates between the cohort participants and the total population were found for all variables, except for maternal epilepsy, chronic hypertension and pre-eclampsia. There was a strong under-representation of the youngest women (<25 years), those living alone, mothers with more than two previous births and with previous stillbirths (relative deviation 30-45%). In addition, smokers, women with stillbirths and neonatal death were markedly under-represented in the cohort (relative deviation 22-43%), while multivitamin and folic acid supplement users were over-represented (relative deviation 31-43%). Despite this, no statistically relative differences in association measures were found between participants and the total population regarding the eight exposure-outcome associations. Using data from the Medical Birth Registry of Norway, this study suggests that prevalence estimates of exposures and outcomes, but not estimates of exposure-outcome associations are biased due to self-selection in the Norwegian Mother and Child Cohort Study.

Smoking during pregnancy from 1999 to 2004: a study from the Medical Birth Registry of Norway.

BACKGROUND: The aims of the study were to describe changes in smoking habits and evaluate secular trends among all Norwegian pregnant women during the period 1999-2004. We wanted to investigate whether there was a general decline in smoking habits among pregnant women. We also wanted to identify population subgroups with diverging trends. METHODS: The Medical Birth Registry of Norway (MBR) has national coverage of all births of 16 or more gestational weeks. Since 1999, women have been asked about tobacco smoking at the beginning and at the end of pregnancy. We included records from 304,905 women giving birth in the period January 1999 through April 2004. Women born outside Norway were handled separately. The selection left a dataset containing 259,573 Norwegian-born women. RESULTS: We obtained information on smoking habits from 86% at the end of pregnancy. Among those, the daily smoking prevalence was reduced from 17.3% in 1999-2001 to 13.2% in 2002-2004. Higher smoking prevalence was found among multiparous (3+), teenage mothers, single women, and women with low educational level. CONCLUSIONS: From 1999 to 2004, a substantial decline in smoking prevalence among Norwegian pregnant women was identified in all subgroups. However, an increasing social polarisation with regard to education and smoking habits was observed in the study period. In order to reduce the smoking-related risks for unsuccessful pregnancy outcome, special attention should be paid to smoking habits among multiparous, teenage women, single women and women with low education.

Mortality after long-term sickness absence: prospective cohort study.

BACKGROUND: The study estimated the excess mortality after long-term sickness absence (LTSA), and identified socio-demographic and diagnostic risk factors of death. METHODS: Prospective cohort study during 1994-2003 in a Norwegian county with 256,654 inhabitants aged 16-62 years. A representative sample of 3386 persons with a spell of sickness absence >8 weeks was compared with the total county population with respect to all cause mortality. Comparative mortality figures (CMF) for the total sample and standardized mortality rates for diagnostic groups were calculated. RESULTS: The CMFs were 1.5 (95% CI 1.1-1.9) for the female and 2.0 (95% CI 1.7-2.4) for the male sample. Among women, persons' sickness certified with cancer contributed with 43% of all deaths and standardized mortality ratios (SMR) was 16.1 (11.2-23.2). The respective figure for the men was 27% and SMR was 8.0 (5.7-11.1). SMR for men with mental diagnoses was 1.7 (95% CI 1.1-2.9) and for 'other' (respiratory, neurological, digestive) 1.8 (95% CI 1.3-2.7). Musculoskeletal cases had not elevated SMRs. Cox proportional hazard analysis with musculoskeletal cases as reference adjusted for age and income showed very high hazard ratios (HR) for cases with cancer diagnoses. Among the men, mental and 'other' diagnoses had also HR above unity. CONCLUSION: The study verified findings from Finland and the UK of excess mortality after LTSA, also when compared with the total population of the same age. Among women, cancer cases explained all the excess mortality, whereas other cases outside the musculoskeletal group also contributed among men.

Long-term sickness absence and disability pension with psychiatric diagnoses: a population-based cohort study.

Sickness absence certified with psychiatric diagnoses is increasing in many Western countries. A substantial proportion of the sickness absentees never return to work, but ends up with a permanent disability pension (DP). This study investigated the incidence of long-term sickness absence (LTSA) with different psychiatric diagnoses, and tested predictors of the transition to permanent DP. A special objective was to explore previously reported gender differences, using a population-based cohort study. The population at risk of LTSA was 106,674 occupational active men and 89,356 women in a Norwegian county in 1994; 314 women and 203 men with LTSA >8 weeks, certified with a psychiatric diagnosis, were followed to the end of 1999, with DP as the endpoint. Diagnoses on sickness certificates, age, gender and income were used as explanatory variables in Cox regression analysis. Annual incidence of LTSA with a psychiatric diagnosis was 7.0/1000/year for women and 3.8/1000 for men; 72% of the women and 50% of the men had a diagnosis indicating depression. During follow-up, 32% of the men and 25% of the women obtained DP. Increasing age, male gender, low income and a diagnosis of psychosis or "other" increased the DP risk. Separate analysis for men indicated a different effect of age and a larger role of serious mental illness. The study verified that women more often than men had LTSA with psychiatric diagnoses, especially with depression. Men were at higher risk of transition to DP, and the study suggested some possible explanations.

Perinatal death and exposure to dental amalgam fillings during pregnancy in the population-based MoBa cohort.

OBJECTIVES: The aim was to gain knowledge regarding the risk of perinatal death related to exposure to dental amalgam fillings in the mother. DESIGN: Population-based observational cohort study. SETTING: The Norwegian Mother and Child Cohort Study, a Norwegian birth cohort of children born in 1999-2008 conducted by the Norwegian Institute of Public Health. PARTICIPANTS: 72,038 pregnant women with data on the number of teeth filled with dental amalgam. MAIN OUTCOME MEASURES: Data on perinatal death (stillbirth ≥ 22 weeks plus early neonatal death 0-7 days after birth) were obtained from the Medical Birth Registry of Norway. RESULTS: The absolute risk of perinatal death ranged from 0.20% in women with no amalgam-filled teeth to 0.67% in women with 13 or more teeth filled with amalgam. Analyses including the number of teeth filled with amalgam as a continuous variable indicated an increased risk of perinatal death by increasing number of teeth filled with dental amalgam (crude OR 1.065, 95% CI 1.034 to 1.098, p<0.001). After adjustment for potential confounders (mothers' age, education, body mass index, parity, smoking during pregnancy, alcohol consumption during pregnancy) included as categorical variables, there was still an increased risk for perinatal death associated with increasing number of teeth filled with amalgam (ORadj 1.041, 95% CI 1.008 to 1.076, p = 0.015). By an increased exposure from 0 to 16 teeth filled with amalgam, the model predicted an almost doubled odds ratio (ORadj 1.915, 95% CI 1.12 to 3.28). In groups with 1 to 12 teeth filled with amalgam the adjusted odds ratios were slightly, but not significantly, increased. The group with the highest exposure (participants with 13 or more teeth filled with amalgam) had an adjusted OR of 2.34 (95% CI 1.27 to 4.32; p = 0.007). CONCLUSION: The current findings suggest that the risk of perinatal death could increase in a dose-dependent way based on the mother's number of teeth filled with dental amalgam. However, we cannot exclude that the relatively modest odds ratios could be a result of residual confounding. Additional studies on the relationship between exposure to dental amalgam fillings during pregnancy and perinatal death are warranted.

Prenatal exposure to dental amalgam and risk of symptoms of attention-deficit and hyperactivity disorder (ADHD).

BACKGROUND: ADHD is multifactorial, including both genetic and environmental factors. The safety of amalgam used in dental treatment has been discussed due to its content of mercury and potential risks for negative neurodevelopmental consequences in the offspring. The aim of the study was to investigate possible associations between symptoms related to ADHD in children of three and five years of age and prenatal exposure to mercury from mothers' amalgam fillings. METHODS: Data from the Norwegian Mother and Child Cohort Study (MoBa) were used. Data were collected by questionnaires sent to participating women in week 17 (Q1) and 30 (Q3) of pregnancy and when the child was three (Q6) and five years of age (Q7). Information about exposure to amalgam during pregnancy was obtained from Q3. Information about symptoms related to ADHD was obtained from Q6 and Q7. Valid data were obtained for 42 163 children at three years of age and 23 392 children at five years of age. Logistic regression models, including mothers' age, education, body mass index, parity, smoking and alcohol consumption during pregnancy, were used to estimate the association between ADHD symptoms and prenatal exposure to amalgam fillings. RESULTS: No significant associations between number of teeth with amalgam filling, amalgam fillings placed or removed during pregnancy, and symptoms related to ADHD in children of three and five years of age were found. CONCLUSIONS: In a large, prospective cohort study, we found no indication of increased risk of ADHD-related symptoms in children prenatally exposed to mother's amalgam fillings.