Defining aging as deterioration of the ability required for the activities of daily living with increasing age, we developed a formula for estimating the age of aging. In 1994 and 1995, a questionnaire survey was conducted for 11, 592 individuals (4, 885 men, mean age 61.6, standard deviation 14.6; and 6, 677 women, mean age 63.2, standard deviation 14.8) who were members of 7 cohorts (5 community-based cohorts and 2 cohorts of examiners at a health-promotion center). The questionnaire included three groups of questions related to medical treatment, aging-related symptoms, and personal care (ADL; Activities of Daily Living) and household management (IADL: Instrumental ADL). Multiple regression analysis was made by sex and age group (over 65 years old, under 65 years old) using age as a dependent variable and the three question categories as explanatory variables. Using multiple regression analysis by question category, five items were abstracted from each of the three groups, so that a total of 15 items were abstracted from all questions. Five items were then abstracted from the 15 by multiple regression analysis, and the predicted aging age for an individual is estimated using this statistical model from the results of the questionnaire survey. The predicted aging age is significantly associated with age (r=0.40-0.49, p=0.0001). The difference between the predicted aging age and age is greater among the older or younger people. The expected predicted aging age is estimated using regression analysis of the predicted aging age on age. Aging level indices by sex and age groups were determined by the difference between the expected predicted aging age and age.
We are planning to carry out an epidemiological study on the risk factor for aging using the aging level indices in seven cohorts.
