ABSTRACT.
Objectives.
Chronic diseases are important predictors of self-rated health (SRH). This study investigated whether multimorbidity has a synergistic or cumulative impact on SRH. Moderation by gender and age was examined.
Methods.
Data originated from the Longitudinal Aging Study Amsterdam (N = 2,046, aged 57–98 years). We assessed the presence of lung disease, cardiac disease, peripheral atherosclerosis, stroke, diabetes mellitus, arthritis, and cancer. SRH was measured with the question “How is your health in general?” including 5 response categories. Generalized ordered probit models were applied; possible synergism was examined by testing for nonlinearity of the association.
Results.
The association between multimorbidity and SRH was nonlinear in that the effect of having a single disease was larger than the added effects of co-occurring diseases. However, from the second disease onward, each additional co-occurring disease caused cumulative declines in SRH. Only in the oldest old (85+), the impact of a single disease was similar to that of co-occurring diseases. Results were similar for men and women.
Discussion.
Our findings help to improve understanding of the impact multimorbidity has on SRH: Having a single disease increases the chance of poor health more than each co-occurring disease, indicating some overlap between diseases or adaptation to declining health.
