Parkinson's disease in Nigeria: A review of published studies and recommendations for future research.

Parkinson's disease (PD) affects 1-2% of individuals above 60 years amounting to over 7 million people worldwide. Thus, PD has become an important contributor to the neurological disease burden. Nigeria is the most populous country in Africa, and alarmingly, approximately 5.25 million Nigerians are above 65 years and are therefore at risk for developing PD. We carried out a critical review of published literature on PD in Nigeria to summarize the findings and to evaluate gaps in knowledge. Seven electronic databases were searched for studies published in English before 18th July 2018. Search terms were ["Parkinson's disease" OR "Parkinson disease" OR "parkinsonian disorders" OR "Parkinsonism"] AND "Nigeria". A total of 44 articles (including eight reviews) published since 1969 were identified and reviewed. Amongst the original research articles, most (23) were on PD symptoms or prevalence. There were only two studies on genetics and two on environmental factors. The estimated crude prevalence of PD in Nigeria was lower (10-249/100 000) compared to studies published in Europe (65.6-12 500/100 000). Our findings suggest that PD is under-diagnosed in Nigeria. Possible environmental risk factors identified include blacksmithing and well-water contaminated with trace metals. Given the rising numbers of the ageing population in Nigeria, more studies to evaluate the prevalence and causes of PD in this country are urgently needed. To this end, more funding, resources and a workforce of well-trained neurologists and scientists are essential to manage the impending health burden of PD and related disorders in this country.