The longitudinal relation between chronic diseases and depression in older persons in the community: the Longitudinal Aging Study Amsterdam
Introduction
It is well known that chronic physical diseases may have a negative effect on psychologic well-being in older persons. In both cross-sectional and longitudinal studies different diseases have been found to be related to depressive symptomatology in older people. People with specific diseases, such as stroke, lung disease, arthritis, myocardial infarction, diabetes mellitus, and cancer, reported more depressive symptomatology compared to those who reported no chronic diseases (e.g., [1], [2], [3], [4], [5], [6]). Furthermore, there is a strong association between depressive symptomatology and the number of chronic diseases [7], [8]. Because substantial numbers of older people have a chronic disease, and comorbidity is no exception, this makes older people especially at risk for depressive symptomatology related to chronic diseases.
Because depression may complicate the assessment and treatment of chronic diseases, and vice versa, it is important to investigate how chronic diseases differentially affect depressive symptoms over time. If some diseases appear to be more likely to lead to depression than others, health professionals can be extra alert for symptoms of depression in older people with these diseases. There are many possible mechanisms by which chronic diseases can lead to depression. On the one hand, biologic mechanisms, such as structural and neurochemical changes of the brain (in stroke) or deficiencies of immune system functioning (in rheumatoid arthritis), may be the cause of depression [5], [9]. On the other hand, depression may be related to psychosocial consequences of the disease, such as physical limitations, loss of function and role, loss of independence, sense of helplessness and negative effects on interpersonal relationships [10], [11]. These mechanisms are not thought to be mutually exclusive. The working of these mechanisms might be specific to specific diseases as well as pervasive and thus independent of type of disease.
Although some diseases were shown to have a specific biologic link with depression (as in stroke), community-based studies have shown that general aspects, such as physical limitations may be more important determinants of depression than specific diagnoses [12], [13], [14]. Therefore, when examining the relation between changes in disease status and depression the explanatory role of physical limitations has to be taken into account.
Despite the important role of general disease aspects such as limitations, the physical ways in which various chronic diseases lead to depression are likely to depend on the specific disease and disease characteristics. In cross-sectional studies that compared the level of psychologic distress experienced in different diseases, people with arthritis and stroke reported the highest levels of depressive symptoms, whereas diabetic and cardiac patients reported the lowest [15], [16]. Physical limitations and the manageability of the illness trough medical and self-care efforts were thought to partly explain these differences. These results, however, are based on cross-sectional designs and, thus, do not provide evidence on a causal direction. To establish a causal direction it is needed to obtain insight into the time of onset of disease in relation to the changes in depressive symptomatology over time. Evidence from prospective community-based studies, in which the longitudinal associations between various chronic physical illnesses and depressive symptomatology are compared is lacking.
The main question addressed in this study is: do people with various chronic diseases differ in the course of depressive symptomatology across time? In addition two subquestions will be examined: can these differences be explained by physical limitations, and can these differences be observed in incident diseases (onset after baseline) as well as in prevalent diseases (present at baseline)?
Section snippets
Sample
The Longitudinal Aging Study Amsterdam (LASA) is a multidisciplinary study focusing on predictors and consequences of changes in autonomy and well-being in the aging population [17]. The sampling and data collection procedures and nonresponse have been described in depth elsewhere [18]. In short, a random sample of older adults (age 55–85 years) stratified by age and sex was drawn from the population registries of 11 municipalities in The Netherlands. The sample was originally drawn for the
Characteristics of the sample
The distribution of characteristics of the study sample is presented in Table 1. At baseline, the mean CES-D score was 7.5 (SD 7.5), with 12.9% of the respondents scoring above the cutoff of the CES-D (⩾16). Depressive symptoms show an increase over time, with a mean score of 8.0 (SD 7.8) (14.9% above cutoff) at T2, and 8.6 (SD 7.6) (17.3% above cutoff) at T3.
The seven chronic diseases measured in this study were highly prevalent among the respondents. At baseline, 43.8% reported no disease,
Discussion
The results support that there are differences in the longitudinal association between specific types of chronic diseases and depressive symptoms. The main findings will be summarized here. Cardiac disease was the only disease that showed associations with depression in all the models. Stroke, cancer, lung disease, and arthritis were all found to be associated with depressive symptoms, whereas atherosclerosis and diabetes mellitus were not. Physical limitations played a mediating role in
Acknowledgements
The Longitudinal Aging Study Amsterdam is financially supported by the Department of Policy for the Aged of the Dutch Ministry of Health, Welfare and Sports. Financial support for the present study was obtained from the Dutch Association for Scientific Research (grant 940-32-023). The authors like to thank Dr. J. Twisk for his statistical advice.
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