Longitudinal insights into comorbidity patterns and burden among middle-aged and older adults with diabetes in China: a nine-year cohort study using CHARLS.

Background: China has the largest diabetic population, accounting for over a quarter of global cases. As a chronic condition frequently accompanied by comorbidities, diabetes requires research on the patterns and burdens of associated conditions, particularly within primary care settings. We aim to provide longitudinal insights into the evolution of comorbidity patterns and burdens among China's diabetic population, examining trends and influencing factors. Methods: We used longitudinal data in five waves (2011-20) of the China Health and Retirement Longitudinal Study (CHARLS). We classified comorbidities into three categories based on their aetiological relationship with diabetes: traditional concordant (TCC), non-traditional concordant (NCC), and discordant (DC). We used generalised estimating equation (GEE) models to identify factors influencing comorbidity burden. Results: Between 2011 and 2020, the prevalence of diabetes among individuals aged ≥45 years in China increased from 6.3% to 17.6%, while diabetes-related comorbidities rose from 5.3% to 16.9%. The most prevalent comorbidities in 2020 were hypertension (68.3%) and dyslipidemia (62.3%). The average number of conditions per diabetic patient increased by 1.5, and the Charlson comorbidity index (CCI) increased by 50%. At the final follow-up, 65.4% of patients had TCC, 92.4% had NCC, and 75.9% had DC. GEE analysis showed that the number (β = 0.034; P = 0.009) and CCI (β = 0.041; P = 0.021) of comorbidities increase with age. Diabetes control was significantly associated with a decrease in both the numbers (β = -0.720; P < 0.001) and CCI of TCC (β = -0.951; P < 0.001), a modest but significant reduction in NCC numbers (β = -0.134; P = 0.021) without a corresponding decrease in its CCI, and no significant association with DC. Conclusions: The increasing comorbidity burden in diabetic patients highlights the need for primary care-centred interventions tailored to comorbidity types. Targeted management of diabetes is instrumental in reducing the severity of comorbidities within the TCC pattern.