Based on a systematic review of the literature, we summarized the scientific evidence concerning occurrence, causes, and consequences of multimorbidity (the coexistence of two or more chronic diseases) in elderly people¹. Findings from the review showed that the prevalence of multimorbidity in older persons ranges from 55% to 98%. In cross-sectional studies, older age, female gender, and low socioeconomic status are factors associated with multimorbidity. These findings are also confirmed by longitudinal studies. The major consequences of multimorbidity are disability and functional decline, poor quality of life, and high health care costs. The results found on multimorbidity and mortality risk were inconsistent.

The few studies already available on multimorbidity have focused on quantifying the phenomenon. Despite some conceptual differences, the common denominator in all the definitions is the number of chronic diseases occurring concurrently. However, patients are more than the sum of their diseases, and the use of a quantitative definition fails to catch the patterns of disease, potentially leading to inadequate care management. It would be beneficial for advancements in the field to develop analytical methods to describe how and why diseases co-occur in the population, to detect the biological mechanisms and to explore specific pathways leading to disease clusters².

1. Marengoni A, Angleman S, Melis R, Mangialasche F, Karp A, Garmen A, et al. Aging with multimorbidity: a systematic review of the literature. Ageing Res Rev 2011; 10(4):430-439.
2. Marengoni A, Fratiglioni L. Disease clusters in older adults: rationale and need for investigation. J Am Geriatr Soc (Letter) 2011; 59(12):2395-2396.