Sex and age-specific multimorbidity profiles among working-age inpatients in China: a comparative network analysis

Background: Multimorbidity substantially increases health and economic burdens, and reduces productivity in working-age individuals. We conducted a study using data from 393,170 working-age inpatients (18–59 years) in Shaanxi, China, collected from 1998 to 2018. We aimed to identify multimorbidity profiles by sex and age and explore multimorbidity patterns using network analysis. Methods: The sampling technique in our study involved forming two cohorts—blood donor and non-blood donor groups—from Shaanxi Province, China, based on age, sex, and region using a 1:1 matching method, resulting in 393,170 inpatient hospitalisation records for the working-age population. A total of 223,524 logistic regressions were conducted to explore statistically significant multimorbidity patterns, combined with network analysis, to create sex-specific and age-sex-stratified multimorbidity networks, identifying hub diseases with the most distinct multimorbidity patterns. Results: Our study found that 46.61% of working-age inpatients had multimorbidity in the baseline hospitalisation dataset, with a higher prevalence in males (51.40%) than in females (41.46%). Males exhibited more complex multimorbidity networks with 1,233 unique multimorbidity patterns compared to 881 in females. Unemployment was associated with a higher multimorbidity risk (OR = 1.09, 95%CI: 1.02–1.15) in males, but had the opposite effect in females (OR = 0.93, 95%CI: 0.89–0.98). Hub diseases common to both sexes included liver diseases, dyslipidemia, fluid/electrolyte/acid–base balance disorders, type-2 diabetes mellitus, hypertension, heart failure, atherosclerosis, and gastritis/duodenitis. Hub diseases’ associated patterns accounted for 66.44% of patterns in males and 58.63% in females. With age, both sexes experienced an increase in multimorbidity proportion and network complexity. Males shifted from respiratory, infectious/parasitic and genitourinary disease-associated patterns to endocrine/nutritional/metabolic and circulatory disease-associated patterns. Females experienced a similar shift, with a notable increase in musculoskeletal/connective tissue disease-associated patterns. Digestive disease-associated patterns remained prevalent across all ages and sexes. Conclusions: Multimorbidity networks in working-age inpatients exhibited greater complexity in males than females, growing with age. Hub diseases’ associated multimorbidity patterns dominated the network and multimorbidity patterns shifted toward endocrine/nutritional/metabolic and circulatory disease-associated patterns with age. Our study could contribute to the development of clinical interventions targeting working-age inpatient multimorbidity.