Background: The aim of this study was to examine the accumulation of chronic physical diseases in Older-Age Bipolar Disorder (OABD) as well as in individuals from the general aging population over a 3-year period. Methods: This prospective longitudinal study compared 101 patients with OABD receiving outpatient care (DOBi cohort) with 2545 individuals from the general aging population (LASA cohort). The presence of eight major chronic diseases was asked at baseline and 3-year follow-up. Total number of diseases was the main outcome measure. Self-rated health (SRH, scale 1-5) was examined as a secondary outcome. Multilevel linear modelling of change was performed to estimate and test the observed change in both samples. Results: At baseline, the number of chronic diseases was lower (b= -0.47, p<0.01) and self-rated health comparable (b=0.27, p=0.13) in DOBi than in LASA. Over 3 years the number of chronic diseases increased faster in DOBi than in LASA (b=0.51 versus b=0.35, p(interaction)=0.03). When corrected for employment, depressive symptoms, waist circumference, smoking, and alcohol use, this difference was no longer significant. SRH decreased faster in DOBi than in LASA (b=-0.24 versus b=-0.02, p(interaction)=0.04). Limitations: Information on chronic diseases was collected using self-report. Conclusions: A faster accumulation of chronic physical diseases and a faster decline in health perception was observed in OABD than in participants from the general population. The observed differences could partly be attributed to baseline differences in psychosocial, lifestyle, and health behaviour factors. Our findings urgently call for the use of integrated care in BD.