Genetic influences underlying self-rated health in older female twins

To examine the genetic and environmental sources of variation in self-rated health (SRH) in older female twins and to explore the roles of morbidity, functional limitation, and psychological well-being as mediators of genetic and environmental effects on SRH.

Cross-sectional analysis of twin data.

Research laboratory.

One hundred two monozygotic and 115 dizygotic female twin pairs aged 63 to 76.

SRH was categorized as good, average, or poor. Morbidity was described using a physician-assessed disease-severity scale together with information about the presence of diabetes mellitus and cancer. Maximal walking speed measured over 10 m was used to assess physical functional limitation; the Mini-Mental State Examination and the Center for Epidemiologic Studies Depression Scale were used to characterize psychological well-being. The contributions of genetic and environmental (defined as familial (shared by siblings) or nonshared (unique to each sibling)) effects were assessed using univariate and multivariate structural equation modeling of twin data.

SRH did not have its own specific genetic effect but shared a genetic component in common with the genetic components underlying liability to disease severity, maximal walking speed, and depressive symptoms. It accounted for 64% of the variation in SRH, with environmental effects accounting for the remaining variation.

The current results suggest that there are no specific genetic effects on SRH but rather that genetic influences on SRH are mediated through genetic influences affecting chronic diseases, functional limitation, and mood.