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Previous case-control studies suggest that recreational physical activity protects against preeclampsia. Using a prospective design, the authors estimated the risk of preeclampsia for pregnant women according to level of physical activity, taking other variables that influence risk into consideration. The data set comprised 59,573 pregnancies from the Norwegian Mother and Child Cohort Study (1999–2006). Information on physical activity and other exposures was extracted from questionnaire responses given in pregnancy weeks 14–22, whereas diagnosis of preeclampsia was retrieved from the Medical Birth Registry of Norway. Estimation and confounder control was performed with multiple logistic regression. About 24% of pregnant women reported no physical activity, and 7% reported more than 25 such activities per month. The adjusted odds ratio was 0.79 (95% confidence interval: 0.65, 0.96) for preeclampsia when comparing women who exercised 25 times or more per month with inactive women. The association appeared strongest among women whose body mass index was less than 25 kg/m2 and was absent among women whose body mass index was higher than 30 kg/m2. These results suggest that the preventive effect of recreational physical activity during pregnancy may be more limited than has been shown in case-control studies and may apply to nonobese women only. [ABSTRACT FROM AUTHOR]

The authors investigated the shape, sex- and age-dependency, and possible confounding of the association between birth weight and systolic blood pressure (SBP) in 197,954 adults from 20 Nordic cohorts (birth years 1910–1987), one of which included 166,249 Swedish male conscripts. Random-effects meta-regression analyses were performed on estimates obtained from age- and sex-stratified analyses within each of the cohorts. There was an inverse association between birth weight and SBP, irrespective of adjustment for concurrent body mass index. The association was linear for males, but for females with a birth weight greater than 4 kg, SBP increased with birth weight (p p p = 0.005) when birth weight was less than or equal to 4 kg. The estimated effect of birth weight on SBP at age 50 years was −1.52 mmHg/kg (95% confidence interval: −2.27, −0.77) in men and −2.80 mmHg/kg (95% confidence interval: −3.85, −1.76) in women. Exclusion of the Swedish conscripts produced nearly identical results. This meta-analysis supports the evidence of an inverse birth weight-SBP association, regardless of adjustment for concurrent body size. It also reveals important heterogeneity in the shape and strength of the association by sex and age. [ABSTRACT FROM AUTHOR]

Asthma is a heterogeneous outcome and how the condition should be measured to best capture clinically relevant disease in epidemiologic studies remains unclear. We compared three methods of measuring asthma in the Danish National Birth Cohort (n>50.000). When the children were 7 years old, the prevalence of asthma was estimated from a self-administered questionnaire using parental report of doctor diagnoses, ICD-10 diagnoses from a population-based hospitalization registry, and data on anti-asthmatic medication from a population-based prescription registry. We assessed the agreement between the methods using kappa statistics. Highest prevalence of asthma was found using the prescription registry (32.2%) followed by the self-report (12.0%) and the hospitalization registry (6.6%). We found a substantial non-overlap between the methods (kappa = 0.21-0.38). When all three methods were combined the asthma prevalence was 3.6%. In conclusion, self-reported asthma, ICD-10 diagnoses from a hospitalization registry and data on anti-asthmatic medication use from a prescription registry lead to different prevalences of asthma in the same cohort of children. The non-overlap between the methods may be due to different abilities of the methods to identify cases with different phenotypes, in which case they should be treated as separate outcomes in future aetiological studies.