Body mass index and age-related cataract: the Shihpai Eye Study.

Objective To investigate the association between body mass index (BMI) (calculated as weight in kilograms divided by the square of height in meters) and cataract in a metropolitan Asian elderly population. Design Population-based cross-sectional study. Age-related cataract was defined as any type of lens opacity (ie, nuclear, cortical, and posterior subcapsular opacity) with a Lens Opacities Classification System III grade of more than 2 in one or both eyes. Weight and height were measured by intensively trained interviewers. Results A total of 2045 subjects 65 years and older in Shihpai, Taipei, were invited to participate, and 1361 (66.6%) completed the survey. Of the subjects, 806 were diagnosed as having age-related cataracts. With a BMI of less than 21.3 as a reference point (odds ratio [OR], 1.00), a U-shaped relationship between BMI and nuclear opacity was demonstrated. A reverse U-shaped relationship was shown for cortical opacity. In the final multiple logistic regression models, BMI and BMI 2 were significantly related to nuclear opacity (BMI data: OR, 0.73 [95% confidence interval {CI}, 0.54-0.98]; and BMI 2 data: OR, 1.01 [95% CI, 1.00-1.01]) and cortical opacity (BMI data: OR, 1.52 [95% CI, 1.04-2.34]; and BMI 2 data: OR, 0.99 [95% CI, 0.98-0.99]). Neither BMI nor BMI 2 was related to posterior subcapsular opacity. Conclusion Body mass index is an independent risk factor for nuclear and cortical opacities, but in reverse direction to each other.