Global Trends in the Incidence, Prevalence and Disability-Adjusted Life Years of Leprosy from 1990 to 2019: An Age-Period-Cohort Analysis Using the Global Burden of Disease Study 2019
Background: Leprosy is a neglected tropical disease, with approximately 200,000 new cases reported worldwide every year. Although there are numerous studies on the epidemiology of leprosy, the age, period, and cohort effects remain poorly understood.
Objective: We present an overview of trends in leprosy incidence, prevalence and disability-adjusted life years worldwide from 1990 to 2019 and associations with age, period, and birth cohort. Data for analysis were obtained from the Global Burden of Disease Study 2019.
Methods: We described incident case, prevalent case, age-standardised incidence, prevalence and disability-adjusted life years rates of leprosy from 1990 to 2019. Subsequently, we calculated overall annual percentage changes, annual percentage changes, and the relative risks of period and cohort using an age-period-cohort model.
Results: From 1990 to 2019, the global age-standardized incidence rate of leprosy decreased from 1.48 per 100,000 to 0.65 per 100,000. Additionally, countries with low Socio-Demographic Index (SDI) demonstrated higher age-standardised incidence, prevalence and disability-adjusted life years rate. The age-standardised incidence, prevalence and disability-adjusted life years rate were significantly higher in males compared to females. Furthermore, the impact of age on leprosy increased with age, peaking at 25–35 years, with the highest prevalence rates observed in the 35–40 age group. Notably, the peak age of leprosy onset increases with SDI. Both the period and cohort effects on leprosy incidence and prevalence showed decreasing trend in middle SDI, low-middle SDI and low SDI countries in recent 30 years and birth cohort later than 1905. However, unfavorable period and cohort effects were noted in high SDI regions.
Conclusion: Leprosy incidence, prevalence and disability-adjusted life years have significantly decreased globally, but remain high in areas with lower SDI. Developing regions should increase public awareness of leprosy risk factors, develop effective control policies to better manage and prevent the disease.