| Summary: | Purpose: The aim of this study was to examine the relationship of physical activity and television (TV) viewing time with retinal vascular caliber in a multiethnic Asian population. Methods: Chinese, Indian, and Malay participants (n = 3866) were examined cross-sectionally in the Singapore Prospective Study Program (2004-2007). Leisure-time physical activity and TV viewing time were assessed by the use of an interviewer-administered questionnaire. Retinal arteriolar and venular calibers were measured from digital retinal photographs. Results: After adjusting for demographic, behavioral, and medical factors, those in the lowest quartile of leisure-time physical activity had a wider venular caliber (by 1.51 µm; 95% confidence interval [CI], 0.01-2.92) compared with those in the highest quartile. Using sex- and ethnicity-specific quartiles, stronger associations were noted in males (2.23 µm; 95% CI, 0.10-4.38) and Chinese (2.52 µm; 95% CI, 0.44-4.59) participants. Females who watched >2 hours of TV per day had a narrow arteriolar caliber (by 1.28 µm; 95% CI, -2.56--0.03), compared with the arteriolar caliber of those who watched less TV. Conclusions: Lower physical activity and higher TV viewing time (in females) were adversely associated with retinal microvascular caliber among Asian adults. Additional cross-sectional and longitudinal studies are needed to further clarify the potential mediating role of the microvasculature in the relationship between these behavioral risk factors and poor cardiometabolic health outcomes.
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