Association between body mass index and myopia in the United States population in the National Health and Nutrition Examination Surveys 1999 to 2008: a cross-sectional study

Background This study investigated the association between body mass index (BMI) and myopia in the United States.

Methods This cross-sectional study included 8,000 participants from the 1999 to 2008 National Health and Nutrition Examination Survey (NHANES).

BMI was classified into four groups: < 18.5, 18.5 – 24.9, 25–29.9, and > 29.9.

Three diagnostic thresholds were used for myopia A\B\C: spherical equivalent ≤ −0.5\−0.75\−1 diopters in the right eye.

Multivariate logistic regression analysis and smooth curve fitting were performed to evaluate the association between BMI and myopia.

Results The incidence of myopia was 39.4%.

BMI was correlated with myopia, with each 1 kg/m^2 increase in BMI associated with a 1% increase in the risk of myopia (OR, 1.01; 95% CI 1.01 1.02; p  < 0.05).

In myopia B, after adjusting for confounding factors, compared with the reference group (BMI 18.5–24.9), participants with a BMI of 25–29.9 and greater than 29.9 had a 14% and 25% increased risk of myopia, respectively (OR 1.14; 95% CI 1.01 1.29; p  = 0.037, OR 1.25; 95% CI 1.08 1.44; p  = 0.003), which was similar to the results for myopic A (OR, 1.15; 95% CI 1.02 1.3; p  = 0.027, OR 1.19; 95% CI 1.03 1.37; p  = 0.018) and myopia C (OR 1.15; 95% CI 1.01 1.31; p = 0.035, OR 1.18; 95% CI 1.01 1.37; p  = 0.032).

Moreover, there was a linear relationship between myopia and BMI (p for nonlinearity = 0.767).

Conclusions Myopia using all three diagnostic thresholds was positively associated with higher BMI.

This suggests a potential association between myopia and higher BMI in the American population, warranting further investigations.