Future prevalence of WHO grade 2 impairment in relation to incidence trends in leprosy: An exploration

Objectives: To explore the relationship between leprosy incidence trends and the future prevalence of World Health Organization (WHO) grade 2 impairment caused by leprosy. Methods: Three scenarios were defined to estimate incidences and prevalences of leprosy impairment beyond 2000, assuming 6%, 12% and 18% annual declines in case detection rate respectively, and 6% impairment among new patients. Case detection data from 1985 to 2000 were used for projecting leprosy incidences up to 2020. To estimate future prevalences of WHO grade 2 impairment, the survival of existing and new impaired individuals was calculated. Results: In the 6% scenario, 410 000 new patients will be detected in 2010 and 250 000 in 2020. The number of people living with WHO grade 2 impairment in these years will be 1.3 and 1.1 million, respectively. The 12% scenario predicts that 210 000 new patients will be detected in 2010 and 70 000 in 2020. The grade 2 prevalences will be 1.2 and 0.9 million, respectively. In the 18% scenario, the incidence will be 110 000 in 2010 and 20 000 in 2020, and the grade 2 prevalences will be 1.1 and 0.8 million, respectively. Conclusions: Declines in numbers of people living with grade 2 impairment lag behind trends in leprosy incidence. The prevalence of people with grade 2 decreases much slower than leprosy incidence and case detection in all three scenarios. This implies that a substantial number of people will live with impairment and will need support, training in self-care and other prevention of disability interventions in the next decades.

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