HDL Cholesterol

Abstract

PURPOSE To compare the contributions of physical activity volume (vPA) and intensity (iPA) to HDL levels in middle-aged women. METHODS A cross-sectional design was used. Subjects were 273 women, mean age 40.1 years, who were nonsmokers and non-obese (BMI <30). HDL was measured by a certified hospital laboratory using the Dimension clinical chemistry system. vPA and iPA were assessed using MTI (formerly CSA) accelerometers worn over the left hip for 7 consecutive days. Each day was divided into 10-minute segments (epochs) for a total of 144 epochs each day and 1008 epochs over the 7 days. The sum of all activity counts over the 1008 epochs was used to index vPA. Subjects were divided into quartiles based on their vPA and the middle-two quartiles were collapsed producing 3 categories of vPA. iPA was calculated by categorizing the activity counts of every epoch as Low Intensity, if the activity counts for that epoch were <30,000 (sedentary to slow walking), Moderate Intensity, 30,000–50,000 counts (slow to fast walking), or High Intensity, >50,000 counts (fast walking to running and beyond). A total of 9 epochs (90 min of activity) over the week had to be accumulated in the High Intensity category for the woman to be classified into that iPA category. If she did not have 90 min of High Intensity activity, the 9 epoch cut-point was used to check for Moderate Intensity. If there was not 90 min of activity within the High or Moderate Intensity categories, then she was classified into the Low Intensity category. RESULTS Mean (± SD) vPA over the week was 2.7 ± 0.8 million activity counts. A total of 145 (53.1%) women were classified in the Low Intensity category, 70 (25.6%) in the Moderate Intensity category, and 58 (21.2%) in the High Intensity category. With age controlled, HDL levels differed across the three vPA categories F=4.1, p=0.044), but not without (F=3.5, p=0.063). On the other hand, HDL levels differed across the iPA categories with age controlled (F=6.9, p=0.009), and with no adjustment for differences in age (F=6.2, 0.014). Specifically, after controlling for age, mean HDL levels were 56.2, 52.2, and 52.1 across the High, Moderate, and Low Intensity categories, respectively, with the High Intensity subjects showing significantly higher levels of HDL than the other two categories of women. After controlling for age and iPA, the association between vPA and HDL was eliminated (F=1.1, p=0.30). However, after adjusting for age and vPA, the relationship between iPA and HDL remained significant (F=4.0, p=0.047). CONCLUSION When weekly duration of activity is at least 90 minutes, intensity of physical activity seems to contribute more to HDL levels in women than total volume of activity.