Sitting behavior in postmenopausal women associated with higher levels of cardiometabolic markers
Total Sitting Time and Sitting Pattern in Postmenopausal Women Differ by Hispanic Ethnicity and are Associated With Cardiometabolic Risk Biomarkers
Introduction and methods
Sitting behavior is associated with weight gain, metabolic syndrome, T2DM and CVD [1-4]. Total sitting time and mean sitting bout duration (a measure of how sitting time is accumulated, be it in short, frequently interrupted sitting bouts or in long, unbroken bouts of sitting) are common measures to study individuals’ sitting habits, and both measures have been detrimentally associated with cardiometabolic factors, often independent of physical activity [4-6]. Total sitting time seems to have a dose-dependent relationship with CVD mortality in older women , and a follow-up study showed that both total sitting time and sitting time accumulated in prolonged patterns were associated with increased risk for CVD . Large racial/ethnic disparities in CV health exist between Hispanic and non-Hispanic populations. Compared with non-Hispanic whites, Hispanics have worse measures of overall CV health, but surprisingly experience lower CVD mortality rates .
The present cross-sectional study investigated associations of total sitting time and pattern of sitting time with cardiometabolic biomarkers in overweight/obese Hispanic (n=102) and non-Hispanic (n=416) postmenopausal women. Total sitting time, as well as mean sitting bout duration (with higher values indicating prolonged patterns and lower values indicating interrupted patterns), were assessed by accelerometer measures and machine-learned algorithms. Participants needed to wear the accelerometer devices for at least 4 days with ≥10 hours of accelerometer wear. Data were combined from 3 separate studies that used identical accelerometers, accelerometer wear protocols, and accelerometer data processing protocols [10-13]. Women enrolled in these 3 studies were aged ≥55 years and had a BMI of at least 25 kg/m². Primary outcome measures of cardiometabolic risk biomarkers included BMI, waist circumference, fasting glucose, fasting insulin, homeostatic model assessment of insulin resistance index (HOMA-IR), and HOMA2-IR. Results were expressed as percentage difference in the geometric mean of each biomarker associated with a 60-minute increase in total sitting time or a 15-minute increase in mean sitting bout duration.
- Hispanic women spent 50.3 fewer minutes sitting per day (P <0.001) and had shorter sitting bout durations by 3.6 minutes (P=0.02) than non-Hispanic women.
- In models adjusted for age, accelerometer wear time, Hispanic ethnicity, education, marital status, physical functioning, and parent study, each additional hour of sitting time was associated with a 1.56% higher BMI (95% CI: 0.80–2.33), 1.71% higher waist circumference (95% CI: 0.62–2.81), 6.38% higher fasting insulin (95% CI: 2.86–10.02), and 7.27% higher HOMA-IR (95% CI: 3.35–11.35) (P-trend<0.01 for all associations).
- After multivariable adjustment, 15-minute increase in sitting bout duration was significantly associated with BMI (1.64%, 95%CI: 0.50%–2.79%, P-trend=0.005), waist circumference (1.93%, 95%CI: 0.31%–3.57%, P-trend=0.020), fasting glucose (1.36%, 95%CI: 0.06%–2.68%, P-trend=0.041), fasting insulin (7.43%,95%CI: 2.19%–12.95%, P-trend=0.005), and HOMA-IR (8.92%, 95%CI: 3.05%–15.13%, P-trend<0.01). Only HOMA-IR (6.02%, 95%CI: 0.56%–11.77%, P-trend=0.031) was significant with sitting bout duration after further adjusting for BMI.
- The association between sitting bout duration and fasting glucose was significantly stronger for Hispanic women (4.84%, 95%CI: 0.50%–9.37%) than for non-Hispanic women (0.90%, 95% CI: -0.40%–2.22%, P-interaction=0.03).
- Nearly all associations of total sitting time and mean sitting bout duration tested with glycemic regulation biomarkers were stronger among obese women (BMI ≥30 kg/m²) than for overweight women (BMI 25–29.9 kg/m²) (P-interaction<0.01).
The results suggest that (1) longer total sitting time and mean sitting bout duration are associated with higher levels of cardiometabolic biomarkers and (2) associations of sitting patterns and fasting glucose vary by ethnicity, with more deleterious associations observed for Hispanic women as compared to non-Hispanic women. Additional studies need to indicate if changes in sitting behavior affect cardiometabolic biomarkers.