High mortality of subjects with endemic ataxic polyneuropathy in Nigeria.
Endemic ataxic polyneuropathy, a neurological syndrome that was thought to be benign, has been shown to persist in some communities in south-western Nigeria, where it was first described in the 1950s. This study was conducted to compare mortality of cases and controls, and to determine if mortality is related to exposure to cyanide from cassava foods. Cases of endemic ataxic polyneuropathy and two groups of controls, one group living in an endemic community and the other group living in a non-endemic community, were followed for 25 months. The outcome was death from medical causes. A total of 5970 subjects, 204 cases and 5766 controls - 4000 controls in the endemic community and 1766 controls in the non-endemic community, were followed. A total of 153 subjects died, 24 cases, 115 controls in the endemic community, and 14 controls in the non-endemic community. Relative risks of death (95% CI), adjusted for age and gender, were 4.5 (2.3-8.9) for cases (P < 0.0001), but 2.6 (1.5-4.6) for controls living in the endemic community (P = 0.001). This study shows that endemic ataxic polyneuropathy decreases survival. The finding of lower risk of death in the community with higher exposure to cyanide from cassava foods indicates that mortality of endemic ataxic polyneuropathy is not associated with exposure to cyanide from cassava foods.