This article will examine the generalizability of markers of aging across samples and cultures and the genetic and environmental influences on them.
As part of two studies, 18 demographic, cognitive, physiological, personality, and behavioral variables were available from 459 twin pairs ranging in age from 40 to 90 years. Twelve markers of aging were identified using stepwise regression. Factor analysis of the markers produced four factors: general knowledge, fluid abilities, cardiovascular functioning, and well-being.
Analysis of twin similarity for the factors suggested that genetic and environmental influences varied greatly. Significant age differences in heritability were found for three of the four factors.
Results indicate one aging theory cannot account for changes in all markers of aging. Aging of various systems occurs as a result of different combinations of genetic and environmental influences.