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- Chen, Qi, et al.
(författare)
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Maternal pre-pregnancy body mass index and offspring attention deficit hyperactivity disorder : a population-based cohort study using a sibling-comparison design
- 2014
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Ingår i: International Journal of Epidemiology. - Oxford, United Kingdom : Oxford University Press. - 0300-5771 .- 1464-3685. ; 43:1, s. 83-90
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Tidskriftsartikel (refereegranskat)abstract
- Background: High maternal pre-pregnancy body mass index (BMI) is associated with increased risk of offspring attention deficit hyperactivity disorder (ADHD). However, the role of unmeasured familial confounding for this association remains unclear.Methods: We conducted a population-based cohort study via linkage of Swedish national and regional registers to investigate maternal pre-pregnancy BMI (underweight: BMI <18.5; overweight: 25≤ BMI <30; obesity: BMI ≥30) in relation to offspring ADHD. We followed 673 632 individuals born in Sweden between 1992 and 2000, with prospectively collected information on maternal pre-pregnancy BMI, until they received an ADHD diagnosis or ADHD medication, death, emigration or 31 December 2009. Hazard ratios (HRs) were estimated by Cox proportional hazards models. Stratified Cox proportional hazards models were applied to data on full siblings to control for unmeasured familial confounding.Results: At the population level, pre-pregnancy overweight/obesity was associated with increased risk of offspring ADHD (HR(overweight) = 1.23, 95% CI = 1.18-1.27, P = 0.01; HR(obesity) = 1.64, 95% CI = 1.57-1.73, P = 0.01), after adjustment for measured covariates. In full sibling comparisons, however, previously observed associations no longer remained (HR(overweight) = 0.98, 95% CI = 0.83-1.16, P = 0.82; HR(obesity) = 1.15, 95% CI = 0.85-1.56, P = 0.38).Conclusions: The results suggested that the association between maternal pre-pregnancy overweight/obesity and offspring ADHD could be ascribed to unmeasured familial confounding.
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- Obel, C., et al.
(författare)
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Is maternal smoking during pregnancy a risk factor for Hyperkinetic disorder? : Findings from a sibling design
- 2011
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Ingår i: International Journal of Epidemiology. - : Oxford University Press (OUP). - 0300-5771 .- 1464-3685. ; 40:2, s. 338-345
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Tidskriftsartikel (refereegranskat)abstract
- Background Studies have consistently shown that pregnancy smoking is associated with twice the risk of hyperactivity/inattention problems in the offspring. An association of this magnitude may indicate behavioural difficulties as one of the most important health effects related to smoking during pregnancy. However, social and genetic confounders may fully or partially account for these findings. Methods A cohort including all singletons born in Finland from 1 January 1987 through 31 December 2001 was followed until 1 January 2006 based on linkage of national registers. Data were available for 97% (N = 868 449) of the population. We followed singleton children of smoking and non-smoking mothers until they had an International Classification of Diseases, 10th revision, diagnosis of hyperkinetic disorder (HKD) or to the end of the observation period. We used sibling-matched Cox regression analyses to control for social and genetic confounding. Results We found a much smaller association between exposure to maternal smoking during pregnancy and risk of HKD in children using the sibling-matched analysis [hazards ratio (HR) = 1.20, 95% confidence interval (CI) 0.97-1.49] than was observed in the entire cohort (HR 2.01, 95% CI 1.90-2.12). Conclusions Our findings suggest that the strong association found in previous studies may be due to time-stable familial factors, such as environmental and genetic factors. If smoking is a causal factor, the effect is small and less important than what the previous studies indicate.
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- Obel, Carsten, et al.
(författare)
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Smoking during pregnancy and hyperactivity-inattention in the offspring—comparing results from three Nordic cohorts
- 2009
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Ingår i: International Journal of Epidemiology. - : Oxford University Press (OUP). - 0300-5771 .- 1464-3685. ; 38:3, s. 698-705
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Tidskriftsartikel (refereegranskat)abstract
- Background Prenatal exposure to smoking has been associated with Attention Deficit Hyperactivity Disorder (ADHD) in a number of epidemiological studies. However, mothers with the ADHD phenotype may ‘treat’ their problem by smoking and therefore be more likely to smoke even in a society where smoking is not acceptable. This will cause genetic confounding if ADHD has a heritable component, especially in populations with low prevalence rates of smoking since this reason for smoking is expected to be proportionally more frequent in a population with few ‘normal’ smokers. We compared the association in cohorts with different smoking frequencies. Methods A total of 20 936 women with singleton pregnancies were identified within three population-based pregnancy cohorts in Northern Finland (1985–1986) and in Denmark (1984–1987 and 1989–1991). We collected self-reported data on their pre-pregnancy and pregnancy smoking habits and followed the children to school age where teachers and parents rated hyperactivity and inattention symptoms. Results Children, whose mothers smoked during pregnancy, had an increased prevalence of a high hyperactivity-inattention score compared with children of nonsmokers in each of the cohorts after adjustment for confounders but we found no statistical significant difference between the associations across the cohorts. Conclusion The estimated association was not strongest in the population with the fewest smokers which does not support the hypothesis that the association is entirely due to genetic confounding.
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- Sundström, Johan, Professor, 1971-, et al.
(författare)
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Risk factors for subarachnoid haemorrhage : a nationwide cohort of 950 000 adults
- 2019
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Ingår i: International Journal of Epidemiology. - : Oxford University Press. - 0300-5771 .- 1464-3685. ; 48:6, s. 2018-2025
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Subarachnoid haemorrhage (SAH) is a devastating disease, with high mortality rate and substantial disability among survivors. Its causes are poorly understood. We aimed to investigate risk factors for SAH using a novel nationwide cohort consortium.METHODS: We obtained individual participant data of 949 683 persons (330 334 women) between 25 and 90 years old, with no history of SAH at baseline, from 21 population-based cohorts. Outcomes were obtained from the Swedish Patient and Causes of Death Registries.RESULTS: During 13 704 959 person-years of follow-up, 2659 cases of first-ever fatal or non-fatal SAH occurred, with an age-standardized incidence rate of 9.0 [95% confidence interval (CI) (7.4-10.6)/100 000 person-years] in men and 13.8 [(11.4-16.2)/100 000 person-years] in women. The incidence rate increased exponentially with higher age. In multivariable-adjusted Poisson models, marked sex interactions for current smoking and body mass index (BMI) were observed. Current smoking conferred a rate ratio (RR) of 2.24 (95% CI 1.95-2.57) in women and 1.62 (1.47-1.79) in men. One standard deviation higher BMI was associated with an RR of 0.86 (0.81-0.92) in women and 1.02 (0.96-1.08) in men. Higher blood pressure and lower education level were also associated with higher risk of SAH.CONCLUSIONS: The risk of SAH is 45% higher in women than in men, with substantial sex differences in risk factor strengths. In particular, a markedly stronger adverse effect of smoking in women may motivate targeted public health initiatives.
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- van Raalte, Alyson, et al.
(författare)
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More variation in lifespan in lower educated groups: evidence from 10 European countries
- 2011
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Ingår i: International Journal of Epidemiology. - : Oxford University Press (OUP). - 0300-5771 .- 1464-3685. ; 40, s. 1703-1714
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Tidskriftsartikel (refereegranskat)abstract
- Background Whereas it is well established that people with a lower socio-economic position have a shorter average lifespan, it is less clear what the variability surrounding these averages is. We set out to examine whether lower educated groups face greater variation in lifespans in addition to having a shorter life expectancy, in order to identify entry points for policies to reduce the impact of socio-economic position on mortality. Methods We used harmonized, census-based mortality data from 10 European countries to construct life tables by sex and educational level (low, medium, high). Variation in lifespan was measured by the standard deviation conditional upon survival to age 35 years. We also decomposed differences between educational groups in lifespan variation by age and cause of death. Results Lifespan variation was higher among the lower educated in every country, but more so among men and in Eastern Europe. Although there was an inverse relationship between average life expectancy and its standard deviation, the first did not completely predict the latter. Greater lifespan variation in lower educated groups was largely driven by conditions causing death at younger ages, such as injuries and neoplasms. Conclusions Lower educated individuals not only have shorter life expectancies, but also face greater uncertainty about the age at which they will die. More priority should be given to efforts to reduce the risk of an early death among the lower educated, e.g. by strengthening protective policies within and outside the health-care system.
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- Yang, Fei, et al.
(författare)
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Moist smokeless tobacco (Snus) use and risk of Parkinson's disease
- 2017
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Ingår i: International Journal of Epidemiology. - : Oxford University Press (OUP). - 0300-5771 .- 1464-3685. ; 46:3, s. 872-880
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Cigarette smoking is associated with a lower risk of Parkinson's disease. It is unclear what constituent of tobacco smoke may lower the risk. Use of Swedish moist smokeless tobacco (snus) can serve as a model to disentangle what constituent of tobacco smoke may lower the risk. The aim of this study was to determine whether snus use was associated with a lower risk of Parkinson's disease.METHODS: Individual participant data were collected from seven prospective cohort studies, including 348 601 men. We used survival analysis with multivariable Cox regression to estimate study-specific relative risk of Parkinson's disease due to snus use, and random-effects models to pool estimates in a meta-analysis. The primary analyses were restricted to never-smokers to eliminate the potential confounding effect of tobacco smoking.RESULTS: During a mean follow-up time of 16.1 years, 1199 incident Parkinson's disease cases were identified. Among men who never smoked, ever-snus users had about 60% lower Parkinson's disease risk compared with never-snus users [pooled hazard ratio (HR) 0.41, 95% confidence interval (CI) 0.28-0.61]. The inverse association between snus use and Parkinson's disease risk was more pronounced in current (pooled HR 0.38, 95% CI 0.23-0.63), moderate-heavy amount (pooled HR 0.41, 95% CI 0.19-0.90) and long-term snus users (pooled HR 0.44, 95% CI 0.24-0.83).CONCLUSIONS: Non-smoking men who used snus had a substantially lower risk of Parkinson's disease. Results also indicated an inverse dose-response relationship between snus use and Parkinson's disease risk. Our findings suggest that nicotine or other components of tobacco leaves may influence the development of Parkinson's disease.
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