The purpose of the Black Elderly Twin Study (BETS) is to estimate the genetic and nongenetic contributions to physical functioning in a population of black twin pairs aged 65 years and older. We propose to identify a national cohort of two populations: 2,985 black twin pairs; plus a control sample of white twin pairs from the Medicare enrollment files of the Health Care Financing Administration (HCFA). Both samples will include male-male and female-female pairs. A baseline telephone interview will be administered to all twin pairs. This interview will include the following measures of physical functioning: Katz Activities of Daily Living, Lawton and Brody Instrumental Activities of Daily Living, Rosow and Breslau Gross Mobility Functions, and Nagi Battery of Physical Performance. The interview will also measure the following factors that may influence physical functioning: specific chronic diseases, cognitive impairment, depression, social functioning, socio-economic status, and health habits (i.e. obesity, tobacco and alcohol use, sleep). In addition, a 12 month health history of all hospitalizations and out-patient visits will be retrospectively reconstructed by record linkage with Medicare computer files. With these data, three primary hypotheses concerning the physical functioning of older blacks can be tested: 1) Additive genetic effects and shared common environment influence the phenotypic variability in physical functioning as measured by each of the physical functioning instruments, 2) For each instrument, individual items measure different dimensions of physical functioning which are influenced by heredity and shared common environment, 3) The effect of specific covariates (such as chronic diseases, cognitive impairment and social function) are mediated through additive genetics, shared common environment or both acting in concert. The strength of the BETS project lies in that it is designed to enhance understanding of physical functioning in older blacks by ascertaining health status measures in a genetically informative sample: The potential contribution of heredity to physical functioning has never been studied in a large population of older U.S. blacks.
