A Twin Study Indicates Time Spent Sitting Correlates with a Faster Pace of Aging
There has been some debate in past years over the degree to which time spent sitting is harmful to long-term health, and whether the negative effects of time spent sitting can be removed by suitable amounts of exercise. We live in a sedentary age, and many people spend most of their working lives in a seat, punctuated by the exercise that they do carry out. Evidently a fully sedentary lifestyle is a bad thing, the evidence is clear on that front. But does extended sitting time cause harms even in those who are exercising to a reasonable degree? The epidemiological evidence leans towards yes, if we're prepared to assume that correlations in human data between sedentary time and health are indicative of causation. In animal studies that causation is well demonstrated, but human data sets can only ever indicate correlation.
We examined whether physical activity buffers high levels of sitting time on cardiovascular and metabolic health indices of total cholesterol/high-density lipoprotein ratio (TC/HDL) and body mass index (BMI) in a sample of young adults. The expected negative associations of sitting on health indices were apparent in this relatively healthy period of adulthood. However, meeting the current physical activity recommendations did not buffer the impacts of sitting on BMI or TC/HDL fully, although engagement in vigorous physical activity is associated with lower, healthier levels.
For females in their early 30s and males in their late 20s, the TC/HDL is shown to cross into the moderate cardiac risk territory when sitting 8.5 hours per day even after meeting current physical activity recommendations. Performing vigorous physical activity reveals a notable age-equivalent benefit with any level of sitting where an individual exercising 30 minutes of day of vigorous intensity exercise has comparable TC/HDL and BMI values to someone 5 or 10 years younger respectively sitting the same amount of time without any vigorous physical activity. Our findings suggest maintaining sedentary behavior throughout young adulthood may contribute to later cardiovascular and metabolic disease susceptibility.
The co-twin control analyses with the monozygotic pairs further illustrates the importance of additional vigorous physical activity in place of sitting time or in addition to prolonged sitting time to improve one's TC/HDL. Failing to disrupt sedentary behavior could set a course towards poorer health and functioning across the lifespan, particularly since once disease onset occurs for many chronic conditions, disease maintenance will be the primary focus of health intervention instead of recovery. This has been illustrated in previous work implicating elevated BMI and dyslipidemia measurements in early adulthood linked to adverse impacts occurring later in life as they relate to issues such as coronary heart disease, stroke, and other major health issues. Given these links, early intervention of suboptimal BMI and TC/HDL values is critical to prevent a multitude of health-related issues past early adulthood.