Case-control studies and risk factors for cataract in two population studies in Nigeria

The aim of this study was to determine and investigate the risks associated with cataract in South Western and North Central Nigeria.

A hospital-based, case-control study was conducted in Lagos (Lagos group), South Western Nigeria, and Kano (Kano group), North Central Nigeria. In this study, 530 subjects with visually impairing cataracts (study group) and 530 age(-) and sex-matched controls (control group) were recruited from patients aged 40 to 89 years attending the ophthalmology clinics at the same hospital. All subjects were examined for the presence/absence of cataract and interviewed about their educational achievements, diarrhea/dehydration crises, urban/rural residence, and ophthalmological conditions. A standardized questionnaire was administered to all subjects. Logistic regression analysis with age adjustment, literacy, outdoor work, body mass index, crowding, regular vegetable intake, heavy alcohol, and cigarette intake was performed. P < 0.05 was considered statistically significant.

Using multivariate regression analysis, after adjustment for age and other demographics factors, low education and no education [adjusted odds ratios (OR) = 2.42 for the Lagos group and 4.10 for Kano group] and a positive history of diarrhea or dehydration crises (adjusted OR = 1.31 for the Lagos group and 2.12 for Kano group) were associated with an increased risk for cataract. Senile cataracts were more common among the Fulani ethnic group (adjusted OR = 2.21) of North Central Nigeria. However, rural or urban residence did not reveal any positive risk for cataract.

The risk of cataract in North Central Nigeria is similar to that in South Western Nigeria. Cataracts were strongly associated with increasing age, with peak age of 55 years and were more common in those with lower education, severe diarrhea and among the members of Fulani in North Central Nigeria.