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The association between rate of change in cognitive function and longevity was investigated with data from the Dutch Longitudinal Study Among the Elderly. A group of 211 Dutch persons aged 65-84 years at baseline (1955-1957) was reexamined twice during an 8-year follow-up period, after which mortality was ascertained through 1983. Cognitive function was assessed based on an adaptation of the Wechsler Memory Scale. Rate of change in cognitive function during the 8 years of follow-up was determined by regression on time for each individual. Cognitive function declined significantly over the 8-year period (mean yearly change, -0.28 units; 95% confidence interval -0.34 to -0.22). The rate of decline in cognitive function was strongly associated with subsequent survival time in the ages 70 years and over, with those with a large decline having a short survival time. No association could be demonstrated in the age group 65-69 years. Adjustment for potential confounders did not affect the magnitude of the association. These findings suggest that the rate of decline of cognitive function is an independent predictor of longevity in older persons.

Weight change, subsequent survival time and cause of death are reported from the Dutch Longitudinal Study among the Elderly. Data consist of a national sample of persons aged 65-99 years. Six hundred and fifty-eight subjects were examined in the baseline years 1955-1957 and were re-examined 5 years later. Vital status and cause of death were ascertained for 604 of these subjects through 1983. Those subjects who experienced a decline in body mass index (BMI, kg/m(2)) during the period of observation, were likely to be in poorer health and have a shorter survival time than those subjects with stable weight, regardless of initial BMI. Weight gain was associated with shorter survival time only in the age group 65-74 and in those with heart disease. Weight loss, on the other hand, was most likely to result in decreased survival time among those ultimately dying of stroke, pneumonia/influenza or heart disease. As such, weight loss may be an indicator of the severity of disease. The noted associations remained, even when those surviving less than two years were omitted from the analyses. Thus, in longer survivors, weight loss may be associated with decreased vitality and decreased ability to survive once a disease becomes apparent.

The burden of human suffering and the costs of money, manpower and material for the treatment and maintaining of disabled and/or chronically ill--particularly ageing and old--people are increasing immensely. Primary prevention--if possible--is therefore urgently needed in this field of health and social care. Prospective longitudinal epidemiological research may provide an important tool to learn more and better about the causes and development of many processes of malfunctioning and the incidence of disabling conditions at higher ages. For several reasons not many major extensive surveys of this kind have been undertaken so far, although a few are now underway. A very brief overview is presented of some main follow-up surveys, primarily where predictors of disability and longevity are involved. Comparability is difficult, results are sometimes conflicting. Good objective health, high scores on certain intelligence and memory tests seem to be good predictors for longevity, good subjective health more or less. In a Dutch survey disabilities with respect to activities of daily life were more strongly related to survival time in women than in men. Some variables indicating the use of health care services correlated all negatively with survival. The complexity of variables to predict better at high age the risks of disabilities, and survival time, requires a.o. sophisticated longitudinal studies, upon the results of which to base an adequate policy response.

Surveys conducted in several countries corroborate the wellknown fact that a large proportion of old-age people take drugs (frequently different types at the same time). The situation in the Netherlands serves as an example in the article.