Self-rated health in a longitudinal perspective: A 9-year follow-up twin study

Objectives. This study first considers age and cohort explanations for age-related changes in mean values and variance in self-rated health. Second, it evaluates the contributions of genes and environments to self-rated health measured longitudinally. Methods. Subjects were participants in the Swedish Adoption/Twin Study of Aging. Self-rated health assessments were collected in four waves over a 9-year follow-up period, from one or both members of 788 twin pairs. Linear mixed effect models were used to test for differences in means and variances. Structural equation modeling provided estimates of genetic and environmental components of variance and contributions to stability. Results. Changes in means and variance within cohorts seem to reflect illness. Earlier-born cohorts are more variable and have lower self-rated health. These cohort differences were not explained by childhood socioeconomic status. Correlations between time points reflect both environmental and genetic factors. Discussion. Both genes and environments contribute to self-rated health longitudinally, and both age and cohort effects are seen. Age-related changes in self-rated health can be attributed to illness. Cohort differences are most likely attributable to socially mediated and individual-specific environmental factors.