Comorbidity of somatic chronic diseases and decline in physical functioning:; the Longitudinal Aging Study Amsterdam.

OBJECTIVE: To assess the association of decline in physical functioning with number of chronic diseases and with specific comorbidity in different index diseases.
METHODS: A longitudinal design was employed using data from 2,497 older adults participating in the Longitudinal Aging Study Amsterdam. Logistic regression analyses were used to determine influence of chronic diseases on change in physical functioning, operationalized using the Edwards-Nunnally index.
RESULTS: Decline in physical functioning was associated with number of chronic diseases (adjusted ORs from 1.58 for 1, to 4.05 for > or =3 diseases). Comorbidity of chronic nonspecific lung disease and malignancies had the strongest exacerbating influence on decline. An exacerbating effect was also found for arthritis in subjects with diabetes or malignancies and for stroke in subjects with chronic nonspecific lung disease or malignancies. A weaker effect than expected was observed for diabetes in subjects with stroke, malignancies, cardiac disease, or peripheral atherosclerosis.
CONCLUSION: Comorbidities involving chronic diseases that share etiologic factors or pathophysiologic mechanisms appear to have a weaker negative influence on decline in physical functioning than expected. Results indicate that combinations of diseases that both influence physical functioning, but through different mechanisms (locomotor symptoms vs. decreased endurance capacity) may be more detrimental than other combinations.