Comorbid health outcomes in patients with schizophrenia: an umbrella review of systematic reviews and meta-analyses

There is no comprehensive umbrella review exploring the connection between schizophrenia and various health outcomes. Therefore, we aimed to systematically review existing meta-analyses about schizophrenia-associated comorbid health outcomes and validate the evidence levels. We performed an umbrella review of meta-analyses of observational studies to explore comorbid health outcomes in individuals with schizophrenia. Searches were conducted across PubMed/MEDLINE, EMBASE, ClinicalKey, and Google Scholar up to September 5, 2023, targeting meta-analyses of observational studies related to comorbid health outcomes in individuals with schizophrenia. We applied AMSTAR2 for data extraction and quality assessment, adhering to PRISMA guidelines. Evidence credibility was evaluated and categorized by evidence quality. Our protocol was registered with PROSPERO (CRD42024498833). Risk and protective factors were analyzed and presented through equivalent odds ratios (eRR). In this umbrella review, we analyzed 9 meta-analyses, including 88 original articles, covering 21 comorbid health outcomes with over 66 million participants across 19 countries. Patients with schizophrenia showed significant associations with multiple health outcomes, including asthma (eRR, 1.71 [95% CI, 1.05-2.78], class and quality of evidence [CE] = non-significant), chronic obstructive pulmonary disease (1.73 [1.25-2.37], CE = weak), pneumonia (2.63 [1.11-6.23], CE = weak), breast cancer of female patients (1.31 [1.04-1.65], CE = weak), cardiovascular disease (1.53 [1.12-2.11], CE = weak), stroke (1.71 [1.30-2.25], CE = weak), congestive heart failure (1.81 [1.21-2.69], CE = weak), sexual dysfunction (2.30 [1.75-3.04], CE = weak), fracture (1.63 [1.10-2.40], CE = weak), dementia (2.29 [1.19-4.39], CE = weak), and psoriasis (1.83 [1.18-2.83] CE = weak). Our study underscores the imperative for an integrated treatment approach to schizophrenia, highlighting its broad impact across respiratory, cardiovascular, sexual, neurological, and dermatological health domains. Given the predominantly non-significant to weak evidence levels, further studies are needed to reinforce our understanding.