EINO HEIKKINEN, JUKKA JOKELA, AND MARJA JYLHÄ
Questions about age-related and age-dependent changes in functional abilities have been a focus of gerontological research for several decades (e.g. Katzet al., 1963; Katz, 1983; Lawton, 1972, 1990; Kane and Kane, 1981; Fillenbaum, 1985; Applegateet al., 1990). The prevalence of chronic conditions increases with advancing age. Only a minority, about 15 per cent, of 75-80-year-olds are healthy in terms of clinically diagnosed diseases (see Svanborg, 1988; Waters et al., 1989; Jylhäet al., 1992). From this point of view the old saying 'ipsa senectus morbus est' suggesting that old age equals disease seems to be true. On the other hand about one-half of 75-80-year-olds regard themselves as healthy (e.g. Shanaset al., 1968; Heikkinenet al., 1983; Jylhäet al., 1992). There are presumably several reasons for this discrepancy. The criteria for good health may change with age, elderly people may adapt to certain symptoms which they accept as the normal consequences of ageing, and not all diseases cause functional limitations capable of reducing an individual's ability to cope with the routines of daily living. Among elderly people the level of functional abilities in particular seems to modulate their perceptions of health (e.g. Jylhäet al., 1986).
The relationship between life expectancy and functional abilities has recently aroused debate amongst the scientific community in the field of ageing research. Some researchers assume that the health and functional abilities of elderly people will improve along with the rectagularization of mortality ( Fries, 1980, 1989; Laslett, 1989). This, they argue, will lead to a shortened period of serious disability with more and more people dying around the age of 85, which has been suggested as the 'natural life-expectancy' of human beings ( Fries, 1980, 1989). The research evidence does not, however, explicitly support this hypothesis. On the contrary there are findings which suggest that the period of disability in the closing years of life is lengthening with the increase in life expectancy (e.g. Guralnik, 1991; Rooset al., 1993) and that natural life expectancy of 85 years is only a hypothetical construct.
The level of functional abilities is associated with autonomy, independence,