The burden of multimorbidity in institutionalized elderly is poorly investigated. We examined the associations of the type of multimorbidity (i.e., physical, mental or both) with the number of hospitalizations and emergency department (ED) visits in nursing home (NH) residents.

This is a cross-sectional study among NH residents. Information on residents’ health, number of hospitalizations in the last 12 months and hospital department of admission (having been seen in ED vs. non) was recorded by NH staff of 175 French NHs (data was collected in 2011). Participants were screened for the presence of several mental (e.g., dementia) and physical conditions (e.g., diabetes).

Data on hospitalization was available for 6076 NH residents. Compared to having no diseases, the concomitant presence of ≥ 2 physical conditions was the multimorbidity type more strongly associated with both the number of hospitalizations (incidence rate ratio (IRR) =1.93; 95% confidence interval (CI) =1.57 − 2.37) and ED visits (odds ratio (OR)= 1.79; 95% CI=1.24 − 2.58). The presence of a mental condition appeared to moderate the associations between physical conditions and hospitalizations, since the estimate effects were lower among people who had both physical and mental conditions, compared to those with only physical conditions. For example, compared to people with ≥ 2 physical conditions, those with multiple physical and mental conditions had lower IRR (IRR = 0.84; 95% CI=0.75 − 0.95) for the number of hospitalizations.

Mental diseases in very old and multimorbid NH residents probably moderate the associations between physical diseases and hospitalizations. To what extent this represents either a mirror of better clinical practice in NHs or the under-recognition from the NH staff of symptoms leading to justifiable hospitalizations remains unclear.