Somatic and psychiatric comorbidity in the general elderly population: results from the ZARADEMP Project

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.

A stratified random sample of 4803 individuals aged > or =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.

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).

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.