The burden of falls is widely known in older adults, though less research has targeted middle-aged adults (40-64 years of age), particularly at the population level. The purpose of this dissertation was to explore the roles of cardiovascular disease, physical activity (PA) intensity, and body anthropometrics on balance among middle-aged adults. Study 1 sought to determine if balance was impaired in middle-aged adults with poor ankle-brachial pressure index (ABPI), a marker of cardiovascular disease. Study 2 determined the associations between PA intensity with odds of having good static balance. Study 3 explored how strongly a variety of anthropometric measures, including two novel ratios, associated with static balance. Studies utilized 1999-2002 and 2003-2004 National Health and Nutrition Examination Survey (NHANES) data. Study 1 included 1,046 middle-aged adults to examine the associations between ABPI and static balance (Romberg Test of Standing Balance) via logistic regression. This study determined middle-aged adults with at-risk ABPI had a significantly higher 3.38 (95%CI 1.66, 6.87) odds of having poor balance, indicating that balance may be an important functional assessment used in conjunction with ABPI to identify those at a higher risk of cardiovascular disease and falls. Using logistic regression, study 2 analyzed data from 1,068 middle-aged adults to examine the associations of light physical activity (LPA) and moderate-vigorous physical activity (MVPA) with static balance. No significant relationships were found between MVPA or LPA and having good static balance in middle age. However, a sub-analysis in older adults (≥65 years) determined every 60- minute increase in LPA was significantly associated with 1.19 (95%CI: 1.09, 1.31) higher odds of good static balance after controlling for covariates, including MVPA. Study 3 included anthropometric measures of body mass index (BMI), waist circumference (WC), calf circumference (CC), thigh circumference (TC), WC/CC, WC/TC, WC/CC2 , and WC/TC2 in 1,050 middle-aged adults. While a number of anthropometric measures were significantly associated with static balance, in both middle-aged males and females, analyses found higher WC/CC2 and WC/TC2 were significantly associated with decreased odds of good static balance. In both genders, area under the curve predictive ability resulted in WC/TC2 followed by WC/CC2 to be the highest predictors of static balance in middle-aged adults. Similarly, older-age males and females with higher WC/CC2 and WC/TC2 have significantly decreased odds of good static balance. Collectively, these findings demonstrate that WC/TC2 and WC/CC2 are good predictors of balance in middle-aged and older adults
