Research finds that 30 minutes of vigorous daily exercise can counteract some of the aging effects of prolonged sitting, although reducing sitting time remains essential.
Study: A twin analysis of early aging biomarkers and associations with sitting time and physical activity. Image credit: Stock-Asso/Shutterstock.com
In a recent study published in PLoS ONEa group of researchers investigated the interaction between physical activity intensity and sedentary behavior in influencing health outcomes, focusing specifically on cardiovascular and metabolic biomarkers in adults aged 28-49 years.
Background
Sitting for longer periods has become common in developed countries due to changes in the work environment and the use of technology. The 2019 coronavirus disease (COVID-19) pandemic has exacerbated this trend, with many United States (US) adults sitting for more than eight hours a day.
A sedentary lifestyle is associated with adverse health outcomes, particularly in the cardiovascular and metabolic domains, and may increase mortality risks comparable to obesity and smoking. In addition, prolonged sitting is associated with obesity and dyslipidemia, highlighting the need to understand its relationship with aging.
Investigation of these dynamics is essential to the development of effective public health strategies that address the health effects of sedentary behavior. Further research is needed to clarify these complex interactions.
About the study
Participants in this study were drawn from the Colorado Adoption/Twin Study of Lifespan Behavioral Development and Cognitive Aging (CATSLife), with recruitment occurring from July 2015 to March 2021. The sample included 1,327 individuals (53 % women) with a mean age of 33.2 years (SD = 4.9).
Ethical approval was obtained from the Institutional Review Boards of the Institute for Behavior Genetics-University of Colorado, Boulder, and the University of California, Riverside. Informed consent was obtained from all participants.
The CATSLife cohort includes two groups: the Colorado Adoption Project, which includes adopted and non-adopted siblings, and the Longitudinal Twin Study, which consists of monozygotic (MZ) and dizygotic (DZ) same-sex twin pairs.
To reduce confounding factors, certain exclusion criteria were applied, such as current pregnancy, non-fasting state during blood draws, and non-completion of necessary measurements by participants. This left 921 participants for the total cholesterol (TC)/high-density lipoprotein (HDL) analysis and 937 for the body mass index (BMI) analysis. Sedentary behavior was self-reported, while physical activity levels were assessed through recreational activity screening questionnaires.
Biomarkers of health, including BMI, TC and HDL, were measured through personal visits and fasting blood draws. The analytic strategy involved the use of linear mixed-effects models to examine the relationships between lifestyle factors and health outcomes, while accounting for covariates such as gender, age and dietary intake.
Two-twin control analyzes were also performed to differentiate family and environmental effects on health measures. Further sensitivity analyzes in discordant MZ twin pairs provided insights into how physical activity may offset the health risks associated with prolonged sitting.
Study results
Descriptive statistics for baseline measures revealed that participants, on average, reported sitting for 60.07 hours per week, equivalent to approximately 8.58 hours per day. The distribution of sitting hours was approximately normal, with no significant gender differences in mean sitting time.
However, significant differences were observed between males and females on several measures, including strenuous metabolic equivalent tasks (METs), fruit and vegetable intake, BMI and TC/HDL ratio, with males showing higher values (p ≤ 0.005) . . The correlation between BMI and TC/HDL was moderate, as evidenced by a Spearman’s rank correlation coefficient of 0.41.
Linear mixed effect (LME) models were used to analyze sociodemographic effects on TC/HDL and BMI. Results showed significant effects of age and gender on both outcomes, with age being positively associated with higher TC/HDL (B = 0.029, p < .001) and BMI (B = 0.087, p = .004).
While race and ethnicity did not yield significant effects, they were retained in subsequent models. Nonlinear trends were examined but found to be insignificant. Findings suggested that elevated METs were associated with lower TC/HDL ratios, while older age, male gender, and longer sitting times were associated with worse TC/HDL outcomes.
Although a healthy diet was associated with lower TC/HDL ratios, these effects were not statistically significant. Specifically, a 30-year-old who sits for an average of four hours a day will have comparable TC/HDL to a 35-year-old who does 30 minutes of vigorous exercise daily.
Similar patterns emerged for BMI, indicating that those meeting the exercise recommendations could maintain a TC/HDL ratio that placed them in a moderate risk category for cardiovascular problems in early adulthood.
Same-twin control analysis showed significant within-pair effects for sedentary and vigorous physical activity on TC/HDL, suggesting a possible exposure effect rather than familial confounding. However, the MZ within-pair effect for vigorous activity was smaller, indicating partial confounding. Between-pair effects for vigorous exercise were noted but not significant.
Nondiscordant analysis of MZ twins demonstrated that twins who were less sedentary and engaged in more vigorous activity had lower TC/HDL ratios, particularly when vigorous activity replaced sitting time at a ratio of at least 10 minutes of exercise for every hour of sitting.
In contrast, the Active Compensator group required significantly more vigorous activity to achieve similar TC/HDL levels compared to their Active Replacer counterparts, highlighting the differential effect of physical activity on health outcomes in twin pairs.
conclusions
In summary, the findings showed that sitting negatively affected health, and current exercise recommendations did not fully reduce these effects.
Engaging in vigorous activity was associated with healthier TC/HDL levels and BMI, with those sitting for 8.5 hours daily having moderate heart risk.
The co-twin control analysis highlighted the importance of exceeding current exercise guidelines. Furthermore, while fruit and vegetable intake was significant for BMI, it was not associated with TC/HDL, indicating complex dietary influences.
