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- Berhan, Yonas, 1970-
(författare)
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Epidemiological studies of childhood diabetes and important health complications to the disease
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background and aims: The overall aim of this thesis was to increase knowledge regarding the occurrence of childhood onset T1D and T2D in Sweden and in relation to that describe and elucidate important aspects on two grave complications to diabetes; end-stage renal disease (ESRD) and mortality. The two first studies included in this thesis aimed to describe and analyze the cumulative incidence of childhood onset T1D in Sweden and to assess the occurrence of undetected T2D in Swedish children. The aim with the third study was to describe the cumulative incidence of ESRD, and to analyze how ESRD risk differs with age at-onset and sex. The aim of the fourth study was to show how parental socioeconomic status (SES) affects all cause mortality in Swedish patients with childhood onset T1D.Study populations: The foundation for the studies on T1D was data from the Swedish Childhood Diabetes Registry (SCDR). When studying ESRD we also included adult onset T1D cases from the Diabetes Incidence Study in Sweden (DISS). The study on T2D was a population-based screening study where BMI was measured in 5528 school-children and hemoglobin A1c was measured in children with overweight according to international age and sex specific BMI cut-offs. To study ESRD and mortality, we linked the SCDR to various nationwide registers containing individual information on SES, mortality and ESRD.Results: The incidence rates of childhood onset T1D has continued to increase in Sweden 1977–2007. Age- and sex-specific incidence rates varied from 21.6 (95% CI 19.4–23.9) during 1978–1980 to 43.9 (95% CI 40.7– 47.3) during 2005–2007. Cumulative incidence by birth-cohorts has shifted to a younger age at-onset over the first 22 years of incidence registration. From the year 2000 there was a significant reverse in this trend (p<0.01). In contrast to the increase of T1D, we found no evidence of undetected T2D among Swedish school children. Despite a relatively high incidence in T1D in Sweden there is low cumulative incidence of ESRD, 3.3% at maximum 30 years of duration. We found difference between the sexes regarding long-term risk of developing ESRD that was dependent on the age at onset of T1D. When analyzing how socioeconomic status affects mortality in different age at death groups, we found that having parents that received income support increased mortality up to three times in those who died after 18 years of age.Conclusion: The incidence of childhood onset T1D continued to increase in Sweden 1978-2007. Between the years 1978-1999 there was a shift to a younger age at-onset, but from the year 2000 there is a change in this shift indicating a possible trend break. The prevalence of T2D among Swedish children up to 12 years of age is probably very low. There is still a low cumulative incidence of T1D associated ESRD in Sweden. The risk of developing ESRD depends on age at-onset of T1D, and there is a clear difference in risk between men and woman. Excess mortality among subjects with childhood onset T1D still exists, and low parental socioeconomic status additionally increased mortality in this group.
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| 2. |
- Persson, Emma, 1981-
(författare)
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Causal inference and case-control studies with applications related to childhood diabetes
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis contributes to the research area of causal inference, where estimation of the effect of a treatment on an outcome of interest is the main objective. Some aspects of the estimation of average causal effects in observational studies in general, and case-control studies in particular, are explored.An important part of estimating causal effects in an observational study is to control for covariates. The first paper of this thesis concerns the selection of minimal covariate sets sufficient for unconfoundedness of the treatment assignment. A data-driven implementation of two covariate selection algorithms is proposed and evaluated.A common sampling scheme in epidemiology, and when investigating rare events, is the case-control design. In the second paper we study estimators of the marginal causal odds ratio in matched and independent case-control designs. Estimators that, under a logistic regression model, utilize information about the known prevalence of being a case is examined and compared through simulations.The third paper investigates the particular situation where case-control sampled data is reused to estimate the effect of the case-defining event on an outcome of interest. The consequence of ignoring the design when estimating the average causal effect is discussed and a design-weighted matching estimator is proposed. The performance of the estimator is evaluated with simulation experiments, when matching on the covariates directly and when matching on the propensity score.The last paper studies the effect of type 1 diabetes mellitus (T1DM) on school achievements using data from the Swedish Childhood Diabetes Register, a population-based incidence register. We apply theoretical results from the second and third papers in the estimation of the average causal effect within the T1DM population. A matching estimator that accounts for the matched case-control design is used.
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