Objective: To analyze whether functional decline from age 80 to 85 is influenced by changes in self-reported tiredness in daily activities in the preceding 5-year period.
Method: A prospective study of 226 75-year-old men and women with 5- and 10-year follow-up in the Western part of Copenhagen County. Tiredness in daily activities was measured at age 75 and 80 by a validated scale. Changes in tiredness from age 75 to 80: 1) Sustained no tiredness, 2) not tired–tired, 3) tired–not tired, 4) sustained tiredness. Functional decline from age 80 to 85:1) Sustained no need of help; 2) need of help at age 85, alive; 3) need of help at age 85 or dead; 4) dead.
Results: The analyses among the survivors showed a slight tendency to an association between having sustained tiredness or development of tiredness from age 75 to 80 and functional decline from age 80 to 85. Persons with sustained tiredness from age 75 to 80 were at significantly larger risk of functional decline and mortality from age 80 to 85. These results were not attenuated when adjusted by the covariates.
Conclusion: The results in the present study indicate that it is important to take continuous complaints about tiredness in daily activities seriously, because this is an early sign of functional decline.
ADL = activities of daily living;, Mob-T = mobility-tiredness;, Mob-H = mobility-help;, CES-D = Center for Epidemiological Studies Depression Scale;, WHO ICD-8 = World Health Organization International Classification of Diseases-8.
During the last decade public health professionals and clinicians have shown increasing interest in primary prevention of disability among older people who are not disabled (1, 2). In this group of people it might be useful to identify individuals at high risk for functional decline before it occurs by characterizing an early functional state that is associated with later disability.
During the last 10 years a few examples of such early functional states have been demonstrated. These studies showed that poor performance on tests of physical skills are highly predictive of subsequent disability among nondisabled older persons living in the community (3–6). However, under some circumstances, eg, at the general practitioner or at preventive home visits self-report measures have the advantage of requiring less training, less equipment, and less time to administer than performance measures (7). A few studies have shown that self-reported difficulty with ADL (8, 9) and self-report of modification of method of doing a task are independent risk factors of incident disability (10, 11).
In addition to these findings, analyses from Danish and Nordic prospective studies in three different study populations showed that self-reported tiredness in daily activities was strongly related to functional decline. The findings were consistent with follow-ups from age 70 to 75 (12), from age 75 to 80 (13), and with a 1½-year follow-up in two age groups (75 and 80 year olds) (14). However, these studies still leave some unsolved questions:
1. We do not know whether tiredness in daily activities is related to functional decline up to even older ages. Although it is well known that older persons are more likely to decline in function than younger old persons (15, 16), persons aged 80 or more may also be seen as exceptional because they have lived beyond normal life expectancy and in some ways may appear to be a “biological elite”(17). Consequently, factors that predict functional decline may differ for young-old and old-old adults. It has been demonstrated that life satisfaction (18), perceived control (17), and social relations (19, 20) had different effects on mortality among young-olds and old-olds.
2. In the three referred studies (12–14) tiredness in daily activities was measured at one point in time and functional decline from that point of time to follow-up. Two of the studies (12, 13) showed rather large changes in self-reported tiredness over a 5-year period. It is possible that it is the preceding changes that make the difference for subsequent functional decline rather than just tiredness measured at one point in time.
3. All longitudinal studies of old people deal with a considerable selection problem due to large losses to follow-up because of death or nonparticipation for other reasons (21). This may influence the results, especially if functional decline is used as outcome measure, since the most disabled are those who die during follow-up or those who do not participate for other reasons (22, 23). The majority of longitudinal studies about functional decline has restricted the analysis to the survivors (4, 24), thereby disregarding the possible selection problem. Some studies included the dead in the group of most disabled and found that various diseases, education, physical activity (25) and social relations (26) had the same effect on functional decline in the analyses with and without the dead. Other studies demonstrated that socioeconomic position, health (27), and social participation (28) were significantly associated with onset of disability, but only slightly related to mortality. So, the results are contradictory. It seems plausible that some factors are related either to functional decline among those alive or to mortality, while other factors may be related to both functional decline and death. We have earlier shown that tiredness is strongly related to mortality (22, 29). Consequently we believe that tiredness influences functional decline among the living and mortality in the same way and that we would underestimate the true results if we excluded the dead from the analysis of associations between tiredness and functional decline.
The purpose of the present study is to analyze whether functional decline from age 80 to 85 is influenced by changes in self-reported tiredness in daily activities in the preceding 5-year period. Possible selection problems were considered in the following way: First, three outcome measures: 1) functional decline among the survivors, 2) functional decline, including death, assuming that death is part of a general decline pattern, and 3) death were used. Second, we analyzed whether changes in tiredness was related to nonparticipation.
From the Department of Social Medicine, Institute of Public Health, University of Copenhagen (K.A.); Center of Preventive Medicine, Glostrup University Hospital (K.A., M.S.); Danish Veterinary and Food Administration (A.N.P.); and the Department of Geriatric Medicine, Bispebjerg Hospital (M.S.), Copenhagen, Denmark.
Address reprint requests to: Kirsten Avlund, Department of Social Medicine, Institute of Public Health, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark. Email: K.Avlund@socmed.ku.dk
Received for publication July 10, 2002; revision received December 9, 2002.