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Psychosomatic Medicine 65:771-777 (2003)
© 2003 American Psychosomatic Society

ORIGINAL ARTICLES

Functional Decline From Age 80 to 85: Influence of Preceding Changes in Tiredness in Daily Activities

Kirsten Avlund, OT, PhD, Agnes N. Pedersen, MD, PhD and Marianne Schroll, MD, DMedSc

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{at}socmed.ku.dk


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 ACKNOWLEDGMENTS
 REFERENCES
 
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.

Key Words: functional decline, • disability, • tiredness, • changes, • longitudinal design.

Abbreviations: 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.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
METHODS
 RESULTS
 DISCUSSION
 ACKNOWLEDGMENTS
 REFERENCES
 
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 11/2-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.


   METHODS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
RESULTS
 DISCUSSION
 ACKNOWLEDGMENTS
 REFERENCES
 
The study is based on data from the prospective aging studies of 75-, 80- and 85 year-old people at the Center of Preventive Medicine, Glostrup University Hospital, Denmark. The base-line study population included two groups of 75 year-old people: 1) a random sample of 410, 75 year-old men and women born in 1914 (participation rate 72) who took part in the Danish part of the NORA Study (Nordic Research on Aging) (30) and a sample of 338, 75 year-old men and women who had participated in the 70 year-old study 5 years earlier (12). The study took place in 1989 and included a health examination and a home visit with interviews about functional ability and psychosocial factors. The surviving participants from both study groups (N=559) were invited to take part in the 5-year follow-up study (in 1994) when they were 80 years old. This study used the same procedures and methods as the base-line study. Altogether 432 persons agreed to participate in both the home visit and the health examination (participation rate 77%). To select an initially nondisabled cohort we excluded 158 persons reporting need of help in at least one of the following activities: rising from a chair or bed, walking indoors, getting outdoors, walking outside in nice weather, walking outside in poor weather, and managing stairs (N=274). In addition, 48 persons were excluded because of missing values on some of the variables of interest (N = 226). The 10-year follow-up study (85 year-old study) involved five different home visits with focus on 1) functional ability and psychosocial factors, 2) physiological factors and health, 3) psychological factors, 4) oral health, and 5) nutritional status. From 5- to 10-year follow-up, 55 persons had died and 35 surviving subjects did not want to participate. After exclusions the study population for the present investigation consisted of 136 older adults in the analyses among the survivors, 191 persons in the analyses including the deceased as part of a disability pattern and 226 in the analyses with mortality and nonparticipation for other reasons as outcomes.

The protocols in all three surveys were approved by the Ethical Committee of Science in the county of Copenhagen.

Variables
The key determinant variable, tiredness in daily activities, was measured at age 75 and 80 by the Mob-T Scale (31). We asked whether the participants felt tired after performing the following six activities: 1) rising from a chair or bed, 2) walking indoors, 3) getting outdoors, 4) walking out of doors in nice weather, 5) walking out of doors in poor weather, 6) managing stairs. We distinguish persons who did not feel tired and persons who felt tired in one or more of the activities. Changes in tiredness from age 75 to 80 was measured as: 1) Sustained no tiredness, 2) not tired at age 75 - tired at age 80, 3) tired at age 75 - not tired at age 80, 4) sustained tiredness.

The outcome measure, functional ability, was measured at age 80 and 85 by a validated scale (the Mob-H Scale) about need of help in the same activities as in the Mob-T Scale (31). The scale is dichotomized into persons who manage all activities without help (maximum score) and those who need help in one or more activities. Functional decline from age 80 to 85 was measured as 1) sustained no need of help in mobility, 2) need of help at age 85, alive, 3) need of help at age 85 or dead during the follow-up period, assuming that death is part of a general decline pattern, 4) dead during the follow-up period. Figure 1 shows the sequence of the measurements.



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  		Fig. 1. Stability and change in tiredness from age 75 to 80 as predictor of functional decline and death from age 80 to 85.

 
The construct validity of the Mob-T and the Mob-H scales has been accepted by Rasch’ item analysis (31). The scales are reliable (32) and functional ability as measured by the scales was strongly associated with diagnosed diseases (33, 34) , isometric muscle strength (35), simple function tests (35, 36) HREF="#R36-132296">, and postural balance (37).

Covariates
All analyses were adjusted by sex. The following covariates, nearly all measured at the 75 year-old survey, were included as potential confounders, because they were related to functional decline in the study population in earlier analyses with the outcome measured at age 75 or 80 (13, 38–41).

Sociodemographic factors
Individual income: low (only compulsory old age pension), high (both compulsory old age pension and other income sources), and housing tenure: owners, renters, other (most of these are institutionalized).

Social relations measured by 1) Telephone contact with children and friends: weekly and less often. 2) Social participation (three items about a) paying visits to others, b) receiving visits at home and c) participating in social activities outside the home: range 0 to 3, 0 to 1 vs. 2 to 3 points). 3) Membership of club for retired people: Yes, no.

Physical activity measured by the question: "How often do you perform the following activities? - Gardening, active sports, go for walks?" Weekly vs. less often.

Cognitive function measured by a trained psychologist in the 75-year study by the intelligence and memory tests Digit Span, Digit Symbol, Word Fluency, Visual Reproduction, and Raven’s Progressive Matrices (42). Based on factor analysis, these five variables were combined into one measure of cognitive function (41) that expresses the mean factor score for the cognitive function tests. In the present analysis the third with the poorest cognitive function is categorized as having ’poor cognitive function’. This cut point was arbitrarily chosen, but use of other cut points did not essentially change the results.

Depressive symptoms was measured by the Center for Epidemiological Studies Depression Scale (CES-D) based on 20 items, each rated from 0 (rarely or none of the time) to 3 (most of the time), total range 0 to 60. A cut-off score of 16 was used to distinguish individuals with and without depressive symptoms (43, 44).

Chronic disease (13) was measured by the project physician in connection with the medical examination (at the 75 year-old study) by an open question: "Do you suffer from any longstanding illness..."? If the answer was positive, questions were asked about type, localization, duration, medical diagnosis etc. The answers were checked further by asking whether the participant currently or in the past suffered from any of 26 listed impairments, by questions about previous and current use of drugs and by an objective health examination. At the end of the examination day the answers were coded in accordance with WHO ICD-8 (34, 36) . In the present paper we distinguish persons with 0 to 1 vs. 2 to 7 chronic diseases.

Incidence of disease between age 75 and 80 was measured by the following question in the 80-year-old survey: "Did a physician tell you that you have got a new long-standing condition or chronic disease within the last 5 years?" Yes/no. The answers to this question were checked by the project physician as in the 75 year-old survey.

Statistical Analysis
We used three indicators of functional decline: 1) functional decline from age 80 to 85, but alive at age 85 (N = 136), 2) functional decline from age 80 to 85, including the dead (N = 191), and 3) died during the follow-up period (N = 226). In addition we performed the same analyses with nonparticipation at the 85-year survey as outcome measure. Logistic regression analyses were used for all analyses. The first step in the analyses was to test whether the covariates were related to the outcome measures and to changes in tiredness at the bivariate level by chi-square tests. The covariates found to be individually related to either changes in tiredness and/or to one of the outcome measures (p < .20) were then incorporated as independent variables in the logistic regression analyses to determine whether the association between changes in tiredness and functional decline/death was influenced by these factors. The SAS procedure PROBIT was used for all logistic regression analyses.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
DISCUSSION
 ACKNOWLEDGMENTS
 REFERENCES
 
Table 1 demonstrates that about one third of the old persons had sustained good functional ability over the 5 years of follow-up; 13% of the men and 32% of the women deteriorated but stayed alive and 32%/17% of the men/women died.


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  		TABLE 1. Functional Decline, Death and Nonparticipation at 5-Year Follow-up Among 80-Year-Old nondisabled Men and Women
 
Table 2 shows large variations in changes and stability in self-reported tiredness from age 75 to 80. The largest proportion of both men and women had sustained no tiredness from age 75 to 80. About one fifth recovered from tiredness to no tiredness while fewer developed tiredness during the period. 19% of the men and 29% of the women had sustained tiredness from age 75 to 80.


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  		TABLE 2. Changes in Tiredness in Daily Activities Between Age 75 and 80 Among Men and Women
 
The bivariate analyses showed that social participation and depressive symptoms were related to changes in tiredness from age 75 to 80 (p < .05), and that sex (p < .05), housing tenure (p < .20), depressive symptoms (p < .05), incidence of disease (p < .20) were related to at least one of the outcome measures. Consequently these covariates were incorporated in the multivariate logistic regression analyses.

Table 3 shows the associations between changes in tiredness from age 75 to 80 and the three outcomes: 1) functional decline from age 80 to 85, still alive; 2) functional decline from age 80 to 85, including the dead, and 3) dead between age 80 and 85. Columns 2 to 4 show the associations between changes in tiredness in daily activities and functional decline among the survivors. The result of the logistic regression analysis was that there was 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. In addition, women had a larger risk of decline.


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  		TABLE 3. Changes in Tiredness in Daily Activities From Age 75 to 80 as Determinant of Functional Decline From age 80 to 85, Death and Nonparticipation. Results of logistic regression analysisc
 
Columns 5 to 7 demonstrate the associations between changes in tiredness in daily activities and functional decline, including the dead. Persons who developed tiredness from age 75 to 80 tended to have a somewhat larger risk of functional decline and persons with sustained tiredness from age 75 to 80 were at significantly larger risk of functional decline from age 80 to 85. This result was not attenuated when adjusted by the covariates. In addition, persons with incidence of disease from age 75 to 80 had larger risk of functional decline.

When mortality was used as outcome measure (columns 8–10) we found the same patterns of associations: Persons with sustained tiredness from age 75 to 80 had a larger risk of dying (marginally significant). In addition, men and persons with incident diseases from age 75 to 80 had larger risks of mortality. We repeated the crude analyses in a population that included those who participated in the 80-year survey but who had not answered the question about incident disease (N = 274). This gave essentially the same results.

The odds ratios of sustained tiredness from age 75 to 80 on nonparticipation in the 85 year-old survey was 1.3 (CI: 0.5,3.4), the odds ratios of development of tiredness was 1.1 (CI: 0.3,3.4) and of recovery from tiredness: 1.6 (CI: 0.6,4.2) (not in table).


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
ACKNOWLEDGMENTS
 REFERENCES
 
The main finding is that sustained tiredness from age 75 to age 80 was significantly related to functional decline from age 80 to 85, when adjusted by the covariates. We have earlier shown that tiredness in daily activities measured at one point in time is a strong determinant of functional decline (12–14), hospitalization (45), home help (45) and mortality (29). In addition to confirming findings from these studies, we have now demonstrated that the results were equally strong in an old-old population, and that functional decline in old age was more influenced by sustained tiredness over many years than by newly developed tiredness. Thus we have identified a subgroup of independent elderly people who are at risk of becoming disabled.

Tiredness in daily activities may reflect early signs of disability, ie, early signs of difficulties doing daily activities. And seen this way tiredness in daily activities may be regarded as part of The Disablement Process (1), which explains the functional consequences of diseases as a progression from disease through impairments and functional limitations to disability and internal and external factors which accelerate or delay the process. Following this model the questions in the Mob-T Scale and the Mob-H Scale can be regarded as part of a disability pattern in which the single items describe tiredness or need of help in some basic daily activities. It is then plausible that the pathway goes from early signs of disability (tiredness in mobility activities) to actual disability (need of help in mobility). Other studies have shown that those with restricted mobility at base-line had a higher prevalence of difficulties in ADL later on (46–48) and significantly higher rates of both institutionalization and mortality than did those who were mobile (46). The ability to remain mobile is fundamental to overall functioning and plays an important role in the performance of complex strenuous activities such as shopping, housekeeping and food preparation (48).

There is strong evidence that the dimensions in The Disablement Process contribute to tiredness in daily activities. We have found that tiredness in daily activities (measured by the Mob-T Scale) is related to 1) physiological factors, eg, chronic diseases (33, 34); high blood pressure (33); glucose intolerance (33); poor aerobic work capacity (49); poor muscle strength (35); poor balance (37); functional limitations (34–36); 2) psychological factors, eg, cognitive function (41), depressed mood and poor well-being (40); 3) social factors, eg, no education (12, 40); weak social relations (40); and 4) behavioral factors, eg, no physical activity (34, 35, 40). However, when we adjusted the association between tiredness and functional decline by several of these factors in the present and earlier studies, they did attenuate the association, but not so much that this explained the strong associations. It is, however, possible that tiredness in daily activities captures factors that we have not been able to adjust for in the analyses. These factors may be the underlying aging-related physiological decline with a loss of reserve capacity that has not yet caused frank disability, the full array of illnesses in a person and possibly even symptoms of disease as yet undiagnosed but present in a preclinical stage. It is possible that a progressive, but undetected decline in function occurs as a result of disease progression and/or as a result of aging-related biologic changes. This early decline would be a preclinical stage of disability which might show as tiredness in daily activities as an indicator of the speed and direction of functional decline.

The study has both strengths and limitations. The analyses presented here include a relatively small number of subjects. This meant that we could not examine for possible gender differences in patterns of associations between tiredness in daily activities and functional decline. We took this into account by controlling for gender in the multivariate analysis. This did not change the results.

In the present study population of participants who were nondisabled at age 80, the response rate at age 85 was relatively high (84–85%) and tiredness was not related to nonparticipation at follow-up. Consequently we do not believe that the loss to follow-up due to nonparticipation influenced the results in other ways than to make the sample smaller.

With regard to loss to follow-up because of deaths, we found that the associations between tiredness in daily activities and the outcomes were in the same direction for all three outcome measures. This means that exclusion of the dead from the analyses does not result in bias, but in insecure estimations of the associations. This problem is of course of more importance in studies among very old people with many deaths and with long follow-up periods. Consequently we think it has been appropriate to combine the persons who died and those who stayed alive with functional decline in the present study.

The findings may seem surprising having in mind the various patterns of functional change among elderly populations. Rudberg et al. (50) showed an extremely heterogeneous pattern of transitions between different levels of functional ability in a study using four waves of data over a 6-year period. Ferrucci et al. (51) described onset of severe disability among old populations as being progressive (over a period of 2 or more years) or more abrupt or catastrophic. The present results indicate that sustained tiredness in daily activities influences functional decline over a period of 5 years, no matter what kinds of changes take place in between.

We want to underline that the present results are based on an outcome measure that defines a person as having decline if she/he goes from being without help in six mobility activities to being in need of help in one or more of these activities. We chose this cut point because it is highly relevant both for the elderly persons to be independent in their basic daily activities and for those who provide health care to the elderly people. As a result, our findings only pertain to development of disability from a previously disability-free status and do not address other changes in disability status, eg, from ‘some’ to more severe disability. However, functional decline are measured in multiple ways in various studies and it is open for future studies to examine whether the present findings will be the same when other measures of functional decline are used.

It is a strength of the study that the analyses included a measure of chronic diseases and incidence of diseases checked by a physician, cognitive function (measured by a trained psychologist), and well-validated measures of depressive symptoms, tiredness in daily activities (The Mob-T Scale) and actual disability (The Mob-H Scale). To our knowledge no other studies have included tiredness as a category in a measure of functional ability. This measure was originally developed in order to be able to show more variations in functional ability among the relatively well-functioning elderly people (31). But it is possible that tiredness in daily activities reflects both a certain kind of difficulties doing daily activities plus, on top of that, a general feeling of tiredness. We repeated the analyses in Table 3 with general tiredness as a determinant, measured at age 80 by the question: "Have you been hampered by tiredness during the last 14 days?" The results were in the same direction as with tiredness in daily activities, but the odds ratios were smaller, eg, the odds ratio of general tiredness on the combined variable ‘functional decline including the dead from age 80 to 85' was 1.7 (CI: 0.8, 3.4).

We do think it gives more precise information to use a measure of changes in tiredness in daily activities as determinant instead of just using a measure of the determinant at one point. This has made it possible to detect that sustained tiredness for a long time has larger effect on functional decline than newly developed tiredness. As with the outcome measure we are aware of the various patterns of functional change in elderly populations in and out of difficulties doing daily activities (50) and in and out of feelings of tiredness (52). This lack of knowledge about short-term freedom from tiredness or tiredness with short duration is a limitation of the study. However, as with the outcome measure we want to underline, that the present results indicate that sustained tiredness in daily activities from age 75 to 80 influenced functional decline, no matter what kinds of changes took place in between.

Implications
The present study indicates that sustained tiredness in daily activities is an important risk factor for functional decline, even in a very old population. Consequently questions about tiredness in daily activities may be used to identify nondisabled individuals at high risk of functional decline. By eliminating unnecessary efforts toward persons with little likelihood of decline, this strategy of targeted interventions offers clinicians and investigators an efficient approach to decrease the burden of disability in older adults. It is plausible that this group would benefit more from preventive interventions than persons with substantial disability. Crimmins and Saito (53) showed that persons with mild disability were more likely to improve, and Avlund et al. (22) demonstrated that persons who felt tired in their daily activities were more likely to improve than persons in need of help to their daily activities.

The present results indicate that it is important to take these early signs of functional decline seriously, especially if complaints about tiredness in daily activities are continuous, as these people are at a higher risk of becoming dependent of help than others. It is recommended to include this measure of early disability in the preventive work among the elderly as a "trigger" which may prompt referral to further geriatric evaluation, effective intervention and adequate follow-up.


   ACKNOWLEDGMENTS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 ACKNOWLEDGMENTS
REFERENCES
 
The support for this research was provided by research grants from the Danielsen Foundation, the Wedell-Wedellsborg Foundation, The Velux Foundation, and the Interministerial Committee of Applied Research on Aging.

Received for publication July 10, 2002.


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 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 ACKNOWLEDGMENTS
 REFERENCES
 

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