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| 2. |
- Arkkola, Tuula, et al.
(författare)
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Relationship of maternal weight status and weight gain rate during pregnancy to the development of advanced beta cell autoimmunity in the offspring : a prospective birth cohort study
- 2011
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Ingår i: Pediatric Diabetes. - : WILEY. - 1399-543X .- 1399-5448. ; 12:5, s. 478-484
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Tidskriftsartikel (refereegranskat)abstract
- Objective: This study set out to examine how maternal initial body mass index (BMI) and weight gain during pregnancy associate with advanced beta cell autoimmunity in the offspring. Subjects: A population-based birth cohort of 4093 children with increased human leukocyte antigen (HLA)-conferred susceptibility to type 1 diabetes (T1D) and their mothers were recruited between 1997 and 2002 in two university hospital regions in Finland. Methods: The children were monitored for T1D-associated autoantibodies at 3- to 12-month intervals. Advanced beta cell autoimmunity was defined as repeated positivity for islet cell antibodies and at least one of the other three autoantibodies (antibodies to insulin, glutamate decarboxylase and islet antigen 2). Mothers were asked to record the results of the weight measurements during their first and last visits to the antenatal clinic. The initial BMI and weight gain rate were calculated for each woman. Results: Altogether, 175 children developed advanced beta cell autoimmunity or T1D during the follow-up. Maternal BMI before pregnancy or weight gain during pregnancy was not associated with the end-point. Maternal vocational education was associated with child's smaller risk of developing advanced beta cell autoimmunity.
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- Dominicus, Annica, 1976-
(författare)
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Latent variable models for longitudinal twin data
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Longitudinal twin data provide important information for exploring sources of variation in human traits. In statistical models for twin data, unobserved genetic and environmental factors influencing the trait are represented by latent variables. In this way, trait variation can be decomposed into genetic and environmental components. With repeated measurements on twins, latent variables can be used to describe individual trajectories, and the genetic and environmental variance components are assessed as functions of age. This thesis contributes to statistical methodology for analysing longitudinal twin data by (i) exploring the use of random change point models for modelling variance as a function of age, (ii) assessing how nonresponse in twin studies may affect estimates of genetic and environmental influences, and (iii) providing a method for hypothesis testing of genetic and environmental variance components. The random change point model, in contrast to linear and quadratic random effects models, is shown to be very flexible in capturing variability as a function of age. Approximate maximum likelihood inference through first-order linearization of the random change point model is contrasted with Bayesian inference based on Markov chain Monte Carlo simulation. In a set of simulations based on a twin model for informative nonresponse, it is demonstrated how the effect of nonresponse on estimates of genetic and environmental variance components depends on the underlying nonresponse mechanism. This thesis also reveals that the standard procedure for testing variance components is inadequate, since the null hypothesis places the variance components on the boundary of the parameter space. The asymptotic distribution of the likelihood ratio statistic for testing variance components in classical twin models is derived, resulting in a mixture of chi-square distributions. Statistical methodology is illustrated with applications to empirical data on cognitive function from a longitudinal twin study of aging.
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| 6. |
- Murphy, A., et al.
(författare)
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Using multi-level data to estimate the effect of social capital on hazardous alcohol consumption in the former Soviet Union
- 2014
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Ingår i: European Journal of Public Health. - : Oxford University Press (OUP). - 1101-1262 .- 1464-360X. ; 24:4, s. 572-577
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Tidskriftsartikel (refereegranskat)abstract
- Background: Hazardous alcohol consumption is a leading cause of mortality in the former Soviet Union (fSU), but little is known about the social factors associated with this behaviour. We set out to estimate the association between individual- and community-level social capital and hazardous alcohol consumption in the fSU. Methods: Data were obtained from Health in Times of Transition 2010, a household survey of nine fSU countries (n = 18 000 within 2027 communities). Individual-level indicators of social isolation, civic participation, help in a crisis and interpersonal trust were aggregated to the community level. Adjusting for demographic factors, the association of individual- and community-level indicators with problem drinking (CAGE) and episodic heavy drinking was estimated using a population average model for the analysis of multi-level data. Results: Among men, individual social isolation [odds ratio (OR) = 1.20], community social isolation (OR = 1.18) and community civic participation (OR = 4.08) were associated with increased odds of CAGE. Community civic participation (OR = 2.91) increased the odds of episodic heavy drinking, while community interpersonal trust (OR = 0.89) decreased these odds. Among women, individual social isolation (OR = 1.30) and community civic participation (OR = 2.94) increased odds of CAGE. Conclusion: Our results provide evidence of the role of some elements of social capital in problem drinking in the fSU, and highlight the importance of community effects. The nature of civic organizations in the fSU, and the communities in which civic participation is high, should be further investigated to inform alcohol policy in the region.
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| 7. |
- Virtanen, S. M., et al.
(författare)
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Age at introduction of new foods and advanced beta cell autoimmunity in young children with HLA-conferred susceptibility to type 1 diabetes
- 2006
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Ingår i: Diabetologia. - Natl Publ Hlth Inst, Dept Hlth Promot & Chron Dis Prevent, Helsinki 00300, Finland. Tampere Univ, Tampere Sch Publ Hlth, FIN-33101 Tampere, Finland. Tampere Univ Hosp, Res Unit, Tampere, Finland. London Sch Hyg & Trop Med, Dept Epidemiol & Populat Hlth, Med Stat Unit, London WC1, England. Finnish Canc Registry, Helsinki, Finland. Univ Helsinki, Dept Publ Hlth, Helsinki, Finland. : SPRINGER. - 0012-186X .- 1432-0428. ; 49:7, s. 1512-1521
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis: Evidence for the role of infant feeding in the development of beta cell autoimmunity is inconsistent. We set out to study the effects of breastfeeding and of age at introduction of supplementary foods on the development of beta cell autoimmunity. Subjects and methods: A prospective birth cohort of 3,565 infants with HLA-DQB1-conferred susceptibility to type 1 diabetes was recruited between 1996 and 2001 from two university hospital areas in Finland. Blood samples were collected at 3- to 12-month intervals to measure antibodies against islet cells, insulin, glutamate dehydroxylase and islet antigen 2. The families kept a record on the age at introduction of new foods, and for each visit completed a structured dietary questionnaire. The endpoint was repeated positivity for islet cell antibodies together with at least one of the other three antibodies. Results: The overall or exclusive duration of breastfeeding was not associated with the risk of developing the endpoint. An early age at introduction of fruits and berries (<= 4 months) was related to increased risk of developing positivity for the endpoint (hazard ratio [95% CI] for earliest tertile 2.02 [1.03-3.95] and for midtertile 1.97 [1.06-3.64] compared with latest tertile > 4 months). Also, introducing roots between 3 and 3.9 months (midtertile) was related to increased risk of the endpoint (hazard ratio [95% CI] for the earliest tertile 1.04 [0.57-1.90] and for midtertile 1.82 [1.19-2.79] compared with latest tertile). These associations were independent of several putative socio-demographic and perinatal confounding factors. Conclusions/interpretation: Our findings suggest that an early age at introduction of fruits and berries and roots associates independently with beta cell autoimmunity, contradicting earlier findings from smaller birth cohort studies.
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