Trends and inequalities in multimorbidity from 2001/2002 to 2019/2020: A population-based study in British Columbia.

Background: Multimorbidity is a significant challenge for health care systems worldwide. There are limited data, particularly in a Canadian context, on multimorbidity prevalence and incidence, and how these differ by multimorbidity complexity, sex, age, and neighbourhood income quintile.

Methods: This study included administrative data from residents of British Columbia, Canada, from 2001/2002 to 2019/2020. This study analyzed trends in the prevalence and incidence of multimorbidity (two or more conditions) and complex multimorbidity (five or more conditions) by sex, age, and neighbourhood income quintile. This study also identified the most prevalent disease combinations.

Results: More than 25% of adults and 60% of seniors met criteria for multimorbidity in 2019/2020. From 2001/2002 to 2019/2020, age-standardized multimorbidity prevalence increased annually by an average of 1.5% in females and 2.9% in males, and incidence decreased by 3.3% in females and 1.1% in males. Complex multimorbidity prevalence increased annually by an average of 4.8% in females and 5.7% in males, and incidence increased by 1.1% in females and 2.2% in males. Younger age groups had higher average annual increases in multimorbidity prevalence and incidence. Multimorbidity risk was higher in lower income quintiles, relative to higher income quintiles, and these disparities were larger for complex, relative to standard, multimorbidity. Highly prevalent single diseases tended to form the most prevalent disease combinations, and the most prevalent disease combinations varied by income quintile.

Interpretation: These findings suggest that the burden and complexity of multimorbidity continue to rise in British Columbia. Population trends in multimorbidity have important implications for projecting future disease burden and health care planning.