Original article
Somatic and psychiatric comorbidity in the general elderly population: Results from the ZARADEMP Project

https://doi.org/10.1016/j.jpsychores.2008.03.002Get rights and content

Abstract

Objective

In a representative sample of the elderly population in a southern European city, we tested the hypothesis that there is an association between general somatic and general psychiatric morbidity.

Methods

A stratified random sample of 4803 individuals aged ≥55 years was selected for the baseline study in the ZARADEMP Project. The elderly were assessed with standardized Spanish versions of instruments, including the Geriatric Mental State (GMS)–AGECAT. Psychiatric cases were diagnosed according to GMS–AGECAT criteria, and somatic morbidity was documented with the EURODEM Risk Factors Questionnaire.

Results

General comorbidity clustered in 19.9% of the elderly when hypertension was removed from the somatic conditions category, with 33.5% of the sample remaining free from both somatic and psychiatric illnesses. General comorbidity was associated with age, female gender, and limited education, but did not increase systematically with age. The frequency of psychiatric illness was higher among the somatic cases than among noncases, and the frequency of somatic morbidity among the psychiatric cases was higher than among noncases. This association between somatic and psychiatric morbidity remained statistically significant after controlling for age, gender, and education [odds ratio (OR)=1.61; confidence interval (CI)=1.38–1.88]. Most somatic categories were associated with psychiatric illness, but after adjusting for demographic variables and individual somatic illnesses, the association remained statistically significant only for cerebrovascular accidents (CVAs) (OR=1.47; CI=1.09–1.98) and thyroid disease (OR=1.67; CI=1.10–2.54).

Conclusion

This is the first study to document that there is a positive and statistically significant association between general somatic morbidity and general psychiatric morbidity in the (predominantly) elderly population. CVAs and thyroid disease may have more weight in this association.

Introduction

Pioneer studies by authors such as Eastwood and Trevelyan [1] have found that psychiatric and somatic illnesses tend to “cluster” in a limited group of individuals in the general population. The first author speculated about vulnerability to illness, and research in this area was considered “the main task for epidemiology in the field of psychosomatic medicine” [2]. Since then, a considerable number of studies have shown associations between somatic and psychiatric morbidity, both in studies of psychiatric patients identified from inpatient registers [3] and in studies of patients recognized in different medical settings [4], [5]. Furthermore, the negative consequences of coexisting psychiatric morbidity and somatic illness have been documented in a number of reports [6], [7]. While some authors argue that the association between somatic and psychiatric morbidity is now well established, they also underline the fact that previous research has been conducted primarily in clinical samples and/or in a restrictive range of physical or mental conditions [8]. Important population comorbidity studies have been recently conducted by Ormel et al. [9] and Baune et al. [10], but the former focused on heart conditions and the latter focused on depression.

The relevance of studying general comorbidity has been recently shown in the World Mental Health Surveys reported by Scott et al. [8]. Conjoint psychiatric conditions were more strongly associated with several chronic physical conditions than were single mental disorders. Nonetheless, this important survey, similarly to the study by Eastwood and Trevelyan [1], was carried out in predominantly individuals. Therefore, the statement of Eastwood [11] suggesting that the association between general psychiatric morbidity and general somatic morbidity has not been convincingly shown in the elderly population is still valid. Given the relationships between comorbidity and frailty described in the elderly, as well as the negative consequences [12], studies in the older population should become a research priority. Minor psychiatric morbidity, which frequently goes undetected and has been shown to have a negative outcome [13], [14], [15], must be included in new inquiries, and the influence of a specific age group in the association should also be explored. Moreover, in inquiries about general medical comorbidity, the relative weight of specific medical conditions should be studied, since different patterns of association have been reported according to physical disease [10].

Finally, inquiries in new sociocultural settings may give clues to the influence of environmental factors, including factors related to service provision [16]. Roca-Benasar et al. [17] failed to confirm that, in a Spanish island, the frequency of general medical comorbidity in subjects diagnosed with International Classification of Diseases, Tenth Revision (ICD-10) mental disorders was significantly higher than that in respondents without psychiatric diagnosis. Furthermore, Braam et al. [18], in a cross-national European study, found a consistent association of physical illness with depression, but differences between countries were also suggested.

The present study is part of the ZARADEMP Project, an epidemiological inquiry that aims to document in the elderly community the prevalence, incidence, and risk factors of dementia, depression, and psychiatric morbidity, as well as their association with somatic morbidity [19]. The main objective in this study was to try to confirm in a southern European elderly population the tendency of general psychiatric morbidity and general somatic morbidity (specifically conditions considered to be risk factors for dementia) to cluster in some individuals, and to find support for the general hypothesis that there is a positive association between them. If this was confirmed, other objectives were: (a) to document the influence of demographic characteristics in the association, and (b) to explore which specific somatic conditions have more weight in the association.

Section snippets

Background, design overview, sampling, and instruments

The site of the study was Zaragoza, a capital concentrating 622,371 inhabitants (fifth city in the country) or 51% of the population of the historical kingdom of Aragón. The objectives and general methodology of the ZARADEMP Project have been described in more detail in a previous article [19]. It is a longitudinal epidemiological study with three waves, and Wave I (ZARADEMP I) is relevant for this report. It is the baseline cross-sectional study that intended to document the prevalence and

Results

Reliable information related to psychiatric illness was collected in the full sample, and complete information related to somatic illness was collected for 4227 individuals. Demographic characteristics in these patients did not differ significantly from those in the full sample (Table 1). Some data regarding the following somatic illnesses were incomplete or unreliable: hypertension, 426 individuals; angor pectoris, 57 individuals; myocardial infarction, 79 individuals; CVA, 145 individuals;

Discussion

To our knowledge, this is the first study to confirm in the (predominantly) elderly population the clustering of general somatic morbidity and general psychiatric morbidity reported in classical studies in nonelderly adult samples [1]. If hypertension, a condition compatible with a good quality of life, were removed from the somatic conditions, this comorbidity would be found in 19.9% of the elderly, and, at the other extreme, 33.5% of them would be free from either somatic or psychiatric

Acknowledgments

This work was supported by grants 94-1562, 97-1321E, 98-0103, 01-0255, 03-0815, and G03/128 from the Fondo de Investigación Sanitaria and the Spanish Ministry of Health, Instituto de Salud Carlos III, Red de Enfermedades Mentales (REM-TAP Network; Madrid, Spain); CIBERSAM CB07/09/0016 from the Spanish Ministry of Health, Instituto de Salud Carlos III; CICYT SAF93-0453 from the Dirección General de Investigación Científica y Técnica, Secretaría General de Universidades, Madrid, Spain; and

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