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Xerophthalmia and vitamin A deficiency in Nigeria

A national survey to determine the prevalence of xerophthalmia and vitamin A (and other micronutrients) deficiencies was conducted in the four health zones of Nigeria between June and September 1993. The survey was a population-based, cross-sectional study using a two-staged stratified cluster sampling method. Children aged between 6 and 71 months and their mothers were recruited for the study, after having obtained informed consent. Assessment methods consisted of administration of a structured questionnaire, dietary assessment, anthropometrie measurements, ophthalmic examination and conjuctival impression cytology (CIC). Blood samples were also taken and transferred to base laboratories for retinol analysis (using HPLC). The WHO classification and assessment methods1•2 were adopted for the study and adhered to throughout the study. Survey teams consisted of ophthalmologists, ophthalmic nurses and assistants, nutritionists, community health workers, mappers, laboratory technicians and community leaders. A total of 2905 children and their mothers were studied. The national prevalence of xerophthalmia was 1.1 %. The highest prevalence figures were recorded in the south-west (2.2%) and north-east (2%) zones. No single case of xerophthalmia was recorded in the south-east zone. The highest prevalence of xerophthalmia was observed in children aged between 60 and 71 months (2.21%). The national prevalence of nightblindness was 1%. The prevalence figures of the different stages of xerophthalmia against the WHO eut-off points (in brackets) were: XIA= 0, XlB=0.3% (>0.5%), X2NB=0.8% (0.01%), X3NB = 0 (> 0.01%) XS = 0.1 (>0.05). The national prevalence of V AD using serum retinol ( < 20 ug/dl or O. 7 pmol) was 28%. The values ranged from 5 to 134 pg/dl. The national mean (SD) serum retinol value was 31.8 (18.6) pg/dl. The national distribution curve was positively skewed and differed significantly from a normal distribution curve. The highest prevalence figures of V AD using serum retinol were observed in the north-west and north-east zones-49.6% and 48.6%, respectively. During analysis of data, many risk and confounding factors were identified. These include residency, socioeconomic status, maternai education and attitude to breastfeeding, food consumption pattern, nutritional status of children, previous diarrhoeal disease or measles infection, immunization status and deficiency of other micronutrients. The study has shown that xerophthalmia and V AD are highly prevalent, and are of public health significance in Nigeria. This observation is in support of a preliminary report, 3 and other studies from hospital and isolated communities in Nigeria. This study is of particular interest because this was the first time a cross-sectional (national) survey was conducted in Nigeria to establish the prevalence of xerophthalmia and V AD in the country. However, more detailed studies are still required to evaluate the roles of the various risk factors within the context of Nigeria.