Relationship between Physical Activity and Hip Bone Mineral Density for Middle-Aged Women in the United States

Background: Osteoporosis and decline in bone health in the elderly are very common. Such medical problems in middle-aged women can lead to hip fractures and other related problems. Objective: In this research paper, I empirically evaluate whether women in the United States who do the same or higher physical activity (compared to other women of the same age) have different hip bone mineral density at 10 years than women who do less physical activity (compared to other women of the same age) in the USA. Methods: I used the SWAN dataset tracked over 10 years for the same individuals. The sample size is 1513 respondents. The exposure/treatment is physical activity. The outcome variable is total hip bone mineral density. The population is middle-aged women in the USA. I used chained multiple imputations with ordinary least squares regressions along with maximum likelihood logistic and multinomial logistic models using 18 imputations. I also used summary statistics (simple and detailed), chi-squared tests, mean comparison 2-tailed t-tests, correlations, histograms, and ordinary least squares regression estimates with post-estimation tests such as the Breusch-Pagan/Cook-Weisberg test for heteroskedasticity. Results: Both the bivariate and multivariate OLS models show that total hip bone mineral density for middle-aged women in the USA increases (after 10 years) for women who engage in higher physical activity during baseline. I find that women who engage in higher physical activity have, on average, 0.027 higher total hip bone mineral density than women who do not engage in physical activity as much in the USA, ceteris paribus. Conclusions: I found physical activity to be a statistically significant determinant for total hip bone mineral density, along with age, BMI, marital status, race, calcium intake, alcohol consumption, and smoking status for middle-aged women in the United States. I recommend that middle-aged women in the USA participate in physical activity regularly, such as walking, strength training, swimming, etc., to increase their total hip bone mineral density and avoid osteoporosis.