Purpose: Cataract is the most prevalent cause of blindness in Nepal. Several epidemiologic studies have associated cataracts with use of biomass cookstoves. These studies, however, have had limitations, including potential control selection bias and limited adjustment for possible confounding. This study, in Pokhara City, in an area of Nepal where biomass cookstoves are widely used without direct venting of the smoke to the outdoors, focuses on preclinical measures of opacity while avoiding selection bias and taking into account comprehensive data on potential confounding factors.
Methods: Using a cross-sectional study design, severity of lenticular damage, judged on the LOCS (Lens Opacities Classification System) III scales, was investigated in women (n = 143), aged 20 to 65 years, without previously diagnosed cataract. Linear and logistic regression analyses were used to examine the relationships with stove type and length of use. Clinically significant cataract, used in the logistic regression models, was defined as a LOCS III score ≥2.
Results: Using gas cookstoves as the reference group, logistic regression analysis for nuclear cataract showed evidence of relationships with stove type: for biomass stoves, the odds ratio was 2.58 (95% confidence interval, 1.22 to 5.46); and for kerosene stoves, the odds ratio was 5.18 (95% confidence interval, 0.88 to 30.38). Similar results were found for nuclear color (LOCS III score ≥2), but no association was found with cortical cataracts. Supporting a relationship between biomass stoves and nuclear cataract was a trend with years of exposure to biomass cookstoves (p = 0.01). Linear regression analyses did not show clear evidence of an association between lenticular damage and stove types. Biomass fuel used for heating was not associated with any form of opacity.
Conclusions: This study provides support for associations of biomass and kerosene cookstoves with nuclear opacity and change in nuclear color. The novel associations with kerosene cookstove use deserve further investigation.