Abstract
Purpose :
The association between obesity and cataract has been reported with inconsistent findings. The FTO gene (SNP rs9939609) is associated with adult and childhood obesity and therefore an instrumental variable for obesity (by Mendelian randomisation). An interaction between FTO gene and macronutrient intake on the risk of overweight or obesity has been suggested. We aimed to assess the associations between FTO gene (rs9939609), body mass index (BMI) and age-related cataract, and explore whether macronutrient intake modifies the associations in a population-based cohort sample.
Methods :
Of 3654 baseline participants of the Blue Mountains Eye Study (1992-94), 2334 and 1952 were followed 5 and 10 years later (75.8% and 76.7% of survivors, respectively). During the 5-year follow-up, 1174 new participants were examined. Cataract was assessed using lens photographs following the Wisconsin Cataract Grading System. Cumulative cataract was defined as the presence of cortical, nuclear or posterior subcapsular (PSC) cataract at any visit. Imputed dosage data of SNP rs9939609 was used. BMI was calculated as weight (kg)/height (m)2. Dietary data was obtained using a validated food frequency questionnaire. Quintiles of energy-adjusted intakes of macronutrients (carbohydrates, protein and fats) were assessed for their modifying effect on the obesity-cataract associations. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using logistic regression after adjusting for age, sex, hypertension, smoking status, diabetes, education, myopia and steroid use.
Results :
After adjustment, SNP rs9939609 was significantly associated with BMI≥25 (per minor allele increase: OR 1.22, 95% CI 1.08-1.39). There were no significant associations between rs9939609, BMI, or macronutrient intakes and any cataract types. However, significant interaction was found between rs9939609 and protein intake on the odds of PSC cataract (p=0.03). In analyses stratified by quintiles of protein intake, each minor allele of rs9939609 was associated with increased odds of PSC (OR 2.14, 95% CI 1.27-3.60) in the lowest quintile subgroup only.
Conclusions :
Obesity (surrogated by the FTO gene) or BMI was not associated with age-related cataract in the whole study sample. However, in persons with the lowest quintile of protein intake, obesity was associated with PSC cataract. Replication of this finding is needed.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.