Increased mortality from somatic multimorbidity in patients with schizophrenia: a Danish nationwide cohort study

Objective To investigate the association of single- and multimorbidity with mortality rates in patients with schizophrenia compared to the general population. Method A nationwide cohort study including residents in Denmark between 1995 and 2015. The cohort was dichotomously divided by a diagnosis of schizophrenia. Somatic diseases included infections, cancer, endocrine, neurologic, cardiovascular, respiratory, digestive, skin, musculoskeletal, and urogenital diseases. Hazard ratios (HRs) and population attributable fractions (PAFs) were calculated. Results The cohort included 30 210 patients with schizophrenia [mean age (SD) = 32.6 (11.4), males = 57.2%], and 5 402 611 from the general population [mean age (SD) = 33.0 (14.5), males = 50.4%]. All number of somatic diseases were associated with an increased mortality in schizophrenia [HR = 16.3 (95% CI = 15.4-17.3) for 1 disease to 21.0 (95% CI = 19.1-23.0) for >= 5 diseases], using the general population with no somatic disease as reference. Across all somatic diseases, patients with schizophrenia showed a HR > 2, compared to the general population, and respiratory (PAF = 9.3%), digestive (PAF = 8.2%), and cardiovascular (PAF = 7.9%) diseases showed largest contributions to death. Conclusions Patients with schizophrenia showed higher mortality on all levels of multimorbidity, and a doubled mortality rate across all somatic diseases, compared to the general population. The findings suggest that the clusters and trajectories of symptoms associated with schizophrenia is the main driver of the excess mortality.