Table 5.

Methods for calculating YLDs attributable to onchocerciasis-associated epilepsy (OAE)

The disability weight associated with epilepsy depends on the disease severity (see Table 3). We calculated a weighted mean disability weight for epilepsy across the different severity levels, weighting the health state-specific disability weights by the proportion of cases in that health state (Table 4). The proportion of cases in each health state is derived from clinical data of epilepsy severity and frequency in an onchocerciasis hyperendemic area [44]. We assume that the weighted mean disability weights are also applicable to OAE. We multiplied the weighted mean disability weights with the number of prevalent OAE cases to calculate total YLDs attributable to OAE, independently for the various areas. Two types of sensitivity analyses were performed to demonstrate the range in estimates yielded by varying one disability weight value at a time (Additional file 2: Figure S1 and S2). Total YLDs attributable to OAE for 2015 in areas with suspected/reported OAE: 0.336 × 117 000 = 39 300 (95% CI: 16800–148 200) This total estimation of YLDs is based on areas where OAE has been reported or suspected (same 18 areas as stated before). Total YLDs attributable to OAE for 2015 in areas where the presence of OAE has not yet been investigated: 0.336 × 264 000 = 88 700 (95% CI: 36 600–401 500) This total estimation of YLDs is based on onchocerciasis-endemic areas previously under the APOC mandate where OAE has not been reported or suspected.