Myopia has been linked to body weight and sedentary status, but the association with quantitatively measured physical fitness in adults has not been examined. Cross-sectional analyses were performed to investigate the association between physical fitness and myopia in 3,669 military men (aged 29.4 years) in Taiwan. The severity of myopia obtained from the left eye was classified as mild (-0.5 to -3.0 diopters; n = 544), moderate -3.1 to -6.0 diopters; n = 563), and high (<-6.0 diopters; n =150); others were defined as nonmyopia (n = 2,412). Aerobic fitness was evaluated by time for a 3000-meter run test, and muscular endurance was evaluated by numbers of 2-min sit-ups and 2-min push-ups. A value of p < .0125 was considered significant. A multiple linear regression analysis was used to determine the relationship. Individuals who were less physically fit had higher risk of myopia. The associations were dose-dependently significant with mild, moderate, and high myopia for 3000-meter running time (β = 9.64; 95% confidence intervals [3.22, 16.05], β = 12.41; 95% CI [6.05, 18.76], and β = 20.87; 95% CI [9.22, 32.51], respectively) after controlling for the potential covariates. There tended to be an inverse association with moderate and high myopia for numbers of 2-min push-ups (β = -1.38; 95% CI [-2.43, -0.34] and β = -2.10; 95% CI [- 3.97, -0.22], respectively) and 2-min sit-ups (β = -0.83; 95% CI [-1.54, -0.12] and β = -1.29; 95% CI [-2.56, -0.02], respectively), respectively. This study suggested that physical fitness, particularly aerobic fitness of the military males who received regular training, is inversely associated with myopia severity, independent of service specialty, body mass index, and educational level.
Keywords: aerobic fitness; anaerobic fitness; military population; myopia; physical activity; young male adults.