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Study objective: To investigate age, period, and cohort effects an functional status.
Design: A prospective cohort study with measurements in 1981, 1990, and 1996.
Setting: Three municipalities in north east Finland.
Participants: A regionally representative sample of 19 to 63 year old men and women was drawn from the census data in 1979, of which 758 men and 1033 women initially aged 39-63 years entered the study in 1980 and completed the follow up in 1996 (90.9% of the alive cohort).
Measurements and main results: Functional status was determined based on self estimated disabilities (difficulties or not able) to walk 2 km, climb several flights of stairs, and run 100 m. The age adjusted odds of disability in stair climbing and running were lower among the men and the women in 1990 and 1996 than among the men and the women in 1981. There was a declining trend in the odds of disability with succeeding birth cohorts among both the men (odds ratios (OR) 0.79 and 95% confidence intervals (Cl) 0.70 to 0.88 for stair climbing and OR 0.88 and 95% Cl 0.78 to 0.98 for running) and the women (OR 0.85 and 95% Cl 0.77 to 0.93 for stair climbing and OR 0.85 and 95% Cl 0.76 to 0.94 for running). No statistically significant differences in walking disability were found between the study periods or the study cohorts.
Conclusions: The findings depict an improved time trend in functional status in the study population, with implications for future health and social care planning.
Functional status decline represented by inability to perform the usual activities of daily life is a growing health problem among elderly persons. The magnitude of this problem is likely to become substantially greater with the continuing increase in longevity and in the size of the older population age groups in the developed countries. (1) In Finland, life expectancy at birth increased between 1966 and 1999 by eight years among the men and by seven years among the women. In addition, the population projection for 2000-2030 suggests that the proportion of people 65 years and older increases from 15% to 26%. (2)
There is conflicting evidence regarding what gains longevity has meant in health and functioning of the aging populations. Fries (3) suggests that because of healthier lifestyle behaviours, morbidity is compressed into a shorter period before death. In contrast, Schneider and Guralnik (4) argue that the age of onset of morbidity is unchanged, and older persons therefore remain functionally disabled and in poor health for a longer period of time. An important concern for future health and social care planning is whether more recent cohorts of older people are in better or worse health and functioning than previous cohorts.
Longitudinal studies provide the only method for directly studying age related changes in functional status. Several studies among older persons have examined functional status as a predictor of various health outcomes, (5-8) or related it to previously measured risk factors for functional status decline. (9-16) Other studies have estimated transition probabilities or average changes in functional status between two time points. (17-19) Relatively few studies have compared the functional status of similar age groups at two time points, (20-24) and even fewer studies have analysed age related changes in functional status at two or more time points, taking into account the age, period, and cohort effects. (25,26)
The purpose of this study was therefore to analyse 16 year changes in functional status of middle aged and elderly men and women, taking into account the age, period, and cohort effects.
A systematic and representative sample of community based residents aged 19-63 years was drawn from the 1979 census data of a medium size industrial town and two rural municipalities in north east Finland. The result was a sample of 6787 men and women, of whom 5259 (77.5%) answered the baseline survey and formed a study cohort in 1980. According to national census data from the Central Statistical Office of Finland, a total of 340 men and 150 women (9.3% of the study cohort) died between the baseline survey on 1 March 1980 and the follow up survey on 30 September 1996.
The study population consisted of all the men and women who were both alive and between the ages of 55 and 79 years in 1996 (n=1969).
A self administered, postal survey provided data on socio-demographic status, perceived health, chronic conditions, functional status, physical activity, smoking, and alcohol consumption. The questionnaire items have proved to be valid in terms of their relations to the existence of chronic diseases, (27) prediction of coronary heart disease risk, (28) use of physician and hospital services, (29,30) and decreased risk of all cause (29,31,32) and cardiovascular disease (31,32) mortality among middle aged and elderly persons.
The baseline questionnaire was sent to the study cohort at the beginning of 1980. Follow up questionnaires requesting similar information, but with a narrower scope and additional questions on functional status, were sent to all members of the cohort, irrespective of their places of residence in Finland, in 1981, 1990, and to the older members of the cohort in 1996. The response rates for these surveys, after two requests, were 88.0%, 85.4%, and 90.9% of the alive cohort, respectively. A total of 1791 (758 men and 1033 women) responded to the follow up questionnaire in 1996. Of the 178 non-respondents, 133 (6.7% of the alive cohort in 1996) failed to return the questionnaire after two requests, 29 (1.5%) refused to respond, seven (0.3%) did not respond because of a severe health restriction, and nine (0.5%) could not be contacted because of unknown address. The study design of the 16 year prospective follow up study carried out in north east Finland during 1980-1996 is shown in figure 1.
The ethics committee of the Urho Kaleva Kekkonen Institute for Health Promotion Research approved the study.
Functional status …