Current physical activity guidelines may be insufficient to address the health impacts of prolonged sitting, particularly for individuals who sit more than 8 hours daily.
Published in PLOS ONE, researchers analyzed data from 921 adults aged 28 to 49 years to examine associations between sitting time, physical activity, and early cardiovascular and metabolic health biomarkers.
Participants performing 30 minutes of daily vigorous exercise showed total cholesterol/high-density lipoprotein (TC/HDL) ratios comparable to sedentary individuals 5 years younger, and body mass index (BMI) values similar to sedentary individuals 10 years younger, when controlling for equivalent sitting times.
The study found adults sitting approximately 8.5 hours daily, even while meeting current exercise recommendations, entered moderate cardiovascular risk categories during early adulthood. The sample reported an average of 60.1 hours of sitting per week (8.58 hours/day).
Analysis revealed TC/HDL risk classifications as:
- High risk: > 5 for males, > 4.4 for females
- Moderate risk: 3.5-5 for males, 3-4.4 for females
- Optimal: < 3.5 for males, < 3 for females
The investigation included 98 monozygotic and 91 dizygotic twin pairs, allowing researchers to control for genetic and familial confounds. Statistical analysis showed effect sizes for vigorous activity of -0.08 for TC/HDL and -0.11 for BMI (per 1000 vigorous MET minutes weekly, equivalent to 20 minutes of daily jogging).
Males in the study demonstrated significantly higher values compared to females for vigorous METs, TC/HDL, and BMI. A moderate correlation between BMI and TC/HDL was observed.
Analysis of 40 discordant monozygotic twin pairs indicated that replacing sitting time with vigorous activity showed greater effectiveness than compensating for sitting with exercise. For individuals sitting 8 or more hours daily, the data suggest a need for over 80 minutes of vigorous activity weekly to maintain optimal TC/HDL range.
Study limitations included reliance on self-reported activity data rather than objective measurements and limited racial/ethnic diversity in the sample population.
The authors have declared that no competing interests exist.
