Multimorbidity in Thailand: Disease burden, mortality, and geographic distribution

Abstract

Multimorbidity, defined as the coexistence of two or more chronic conditions, poses a significant health challenge in Thailand, particularly during a period of sustained health transition marked by rising prevalence of non-communicable diseases. This thesis explores the patterns, risk factors, spatial distribution, and impact on mortality of multimorbidity among Thai adults, and investigates prevention and management strategies for multimorbidity in Southeast Asia, including Thailand. A systematic review was conducted to assess multimorbidity prevalence in Southeast Asia and its association with education levels. Data from the Thai Cohort Study were analysed using prevalence-based and latent class analysis, logistic regression, spatial analysis, and survival analysis to examine disease clustering, socio-demographic and lifestyle risk factors, geographic distribution, and mortality disparities. A narrative synthesis was conducted to summarise prevention and management strategies. The systematic review revealed multimorbidity prevalence in Southeast Asia ranging from 3.2% to 72.6% among individuals aged 15 years and above. Analysis of Thai Cohort Study data revealed an overall prevalence of multimorbidity of 10%. Metabolic syndrome components including obesity, hyperlipidaemia and hypertension were major drivers of multimorbidity. Age and gender disparities were observed, with higher prevalence among adults aged 60 years and older and among men. Lifestyle factors such as diet (fast food, p-trend = 0.0446; instant food, p-trend = 0.0313) and sleep duration (more than 8 h, AOR = 1.29, 95% CI 1.07-1.55; less than 6 h, AOR = 1.24, 95% CI 1.09-1.41) were positively associated with multimorbidity, while regular exercise including housework (p-trend = 0.0034) was protective. Spatial analysis highlighted higher prevalence in developed areas such as Bangkok and Central Thailand. Latent class analysis identified four clusters: Relatively healthy (87.32%, reference), Metabolic syndromes (10.20%), Cardiometabolic disorders (1.53%), and Multi-system conditions (0.95%). Older age was associated with an increased risk of belonging to the Metabolic syndromes (p-trend = 0.0314), Cardiometabolic disorders (p-trend = 0.0354), or Multi-system conditions (p-trend = 0.0445) clusters. Male gender was also associated with an increased risk of these clusters, while higher education and frequent housework (Cardiometabolic disorders, p-trend = 0.0025) were associated with a lower risk. Central Thailand showed a high age-adjusted prevalence of the Cardiometabolic disorders class (1.47%). Survival analysis indicated a 43% higher risk of death for multimorbid individuals compared to non-multimorbid participants, with age, sleep duration, smoking, and alcohol consumption further increasing mortality risk. This thesis fills research gaps regarding multimorbidity in Thailand and Southeast Asia by providing detailed evidence on prevalence, clustering, socio-demographic and lifestyle determinants, spatial distribution, and mortality impact. The findings highlight the need for targeted prevention and management strategies focusing on metabolic syndrome, age, gender, and lifestyle factors. Tailored healthcare resource allocation in areas with high multimorbidity prevalence is essential to improve outcomes and reduce mortality. Despite increasing research, practical applications in the region remain limited, emphasizing the importance of evidence-based policy, objective data collection, and integrated interventions to alleviate the burden of multimorbidity.