| 1. |
- Björk, Jonas, et al.
(författare)
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An efficient sampling strategy for selection of biobank samples using risk scores
- 2017
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Ingår i: Scandinavian Journal of Public Health. - : SAGE Publications. - 1403-4948 .- 1651-1905. ; 45:17_suppl, s. 41-44
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Tidskriftsartikel (refereegranskat)abstract
- Aim: The aim of this study was to suggest a new sample-selection strategy based on risk scores in case-control studies with biobank data. Methods: An ongoing Swedish case-control study on fetal exposure to endocrine disruptors and overweight in early childhood was used as the empirical example. Cases were defined as children with a body mass index (BMI) ≥18 kg/m2 (n=545) at four years of age, and controls as children with a BMI of 1/217 kg/m2 (n=4472 available). The risk of being overweight was modelled using logistic regression based on available covariates from the health examination and prior to selecting samples from the biobank. A risk score was estimated for each child and categorised as low (0-5%), medium (6-13%) or high (≥14%) risk of being overweight. Results: The final risk-score model, with smoking during pregnancy (p=0.001), birth weight (p<0.001), BMI of both parents (p<0.001 for both), type of residence (p=0.04) and economic situation (p=0.12), yielded an area under the receiver operating characteristic curve of 67% (n=3945 with complete data). The case group (n=416) had the following risk-score profile: low (12%), medium (46%) and high risk (43%). Twice as many controls were selected from each risk group, with further matching on sex. Computer simulations showed that the proposed selection strategy with stratification on risk scores yielded consistent improvements in statistical precision. Conclusions: Using risk scores based on available survey or register data as a basis for sample selection may improve possibilities to study heterogeneity of exposure effects in biobank-based studies.
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| 2. |
- Malmqvist, Ebba, et al.
(författare)
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Maternal Exposure to Air Pollution and Birth Outcomes.
- 2011
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Ingår i: Environmental Health Perspectives. - : Environmental Health Perspectives. - 1552-9924 .- 0091-6765. ; 119, s. 553-558
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Tidskriftsartikel (refereegranskat)abstract
- Background: The knowledge about air pollution effects on birth weight, prematurity and small for gestational age [SGA] in low-exposure areas is insufficient. Objectives: The aim of this birth cohort study was to investigate if low-level exposure to air pollution was associated with prematurity and foetal growth and if there are gender specific effects. Method: We combined high quality registry information on 81110 births with individually modeled exposure data at residence for nitrogen oxides [NOx] and proximity to roads with differing traffic density. The data were analyzed by using logistic and linear regression with and without potential confounders. Results: An increased risk for babies being SGA was observed when highest and lowest NOx quartiles were compared, adjusting for maternal age, smoking, gender and year of birth. After additional adjustment for maternal country of origin and parity (which were highly intercorrelated), the increase was no longer statistically significant. However, in subgroup analysis when highest and lowest NOx quartiles were compared, there was still an increased risk for SGA for baby girls Odds Ratio [OR] 1.12 (95% Confidence Interval [CI] 1.01, 1.24), and also if mothers had not changed residency during pregnancy OR 1.09 (95% CI 1.01, 1.18). The confounders with the greatest impact on SGA were parity and country of origin. Concerning prematurity, the prevalence was lower in the three higher NOx exposure quartiles compared to the lowest category. Conclusion: For future studies on air pollution effects on birth outcomes careful control of confounding is crucial.
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| 3. |
- Martinsson, Matilda, et al.
(författare)
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Intrauterine exposure to perfluorinated compounds and overweight at age 4 : A case-control study
- 2020
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- Aims The aims were to investigate the association between maternal serum levels of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS) and perfluorononanoic acid (PFNA) in early pregnancy and overweight in the child at 4 years and to assess potential heterogeneity in exposure effect between strata with different levels of other risk factors for overweight. Methods We used a case-control design and included 354 cases (ISO-BMI ≥ 18 kg/m2) and 2 controls per case (ISO-BMI ≤17 kg/m2) from child health care centers in Malmö, Sweden. Controls were selected stratified on risk scores for overweight in a propensity score framework. Maternal serum levels were analyzed in biobanked samples collected by routine around gestational week 14. Logistic regression was used to estimate odds ratios between quartiles of maternal serum levels and child overweight at age 4. Results There were no consistent monotonic exposure-response relationships. We found some significant odds ratios in specific quartiles but these were regarded as spurious findings. The absence of an effect was consistent over risk strata. Conclusions We did not find evidence of an association between maternal serum levels of PFOS, PFOA, PFHxS and PFNA in early pregnancy and child overweight at age 4. The level of other risk factors for overweight did not affect children’s susceptibility to prenatal PFAS exposure.
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