For the first time, the 2020 WHO guidelines on physical activity recommend reducing sedentary behaviors due to their health consequences. Less is known on the effect of prolonged occupational sitting, especially in the context of low physical activity engagement.
This study aims at quantifying cardiovascular risk associated with prolonged occupational sitting and determining the additional amount of physical activity that may be needed to attenuate it.
A cohort comprising 481,688 participants in a health surveillance program in Taiwan was followed between 1996 and 2017, collecting data on occupational sitting time, leisure-time physical activity (LTPA) habits, lifestyle, and metabolic parameters. The all-cause and expanded cardiovascular disease (CVD + diabetes mellitus + kidney disease) mortality associated with three occupational sitting volumes (mostly sitting, alternating sitting and non-sitting, mostly non-sitting) was analyzed applying multivariate Cox regression models to calculate the hazard ratios (HRs) for all participants and by subgroups, including five levels of LTPA. Deaths in the first two years of follow-up were excluded to avoid reverse causality.
The study recorded 26,257 deaths during a mean follow-up period of 12.85 years. Individuals mostly sitting at work had a higher mortality risk than those mostly non-sitting, both from all causes (HR: 1.16, 95% CI: 1.11-1.20) and from expanded CVD (HR:1.46, 95% CI:1.35-1.58), after adjusting for gender, age, education, smoking, drinking, and body mass index. Individuals alternating sitting and non-sitting at work did not experience increased risk for all-cause mortality, compared to individuals mostly non-sitting at work (HR: 1.01, 95% CI: 0.97-1.05), but did experience higher risk of deaths due to expanded CVD (HR: 1.13, 95% CI: 1.04-1.23). Individuals engaged in low (15-29 min/day) or no (<15 min/day) LTPA, who mostly sit at work, would need to increase their LTPA by 15 and 30 minutes respectively to reduce their risk of mortality to that of similarly inactive individuals who mostly do not sit at work.
As part of modern lifestyles, prolonged occupational sitting is considered normal and has not received due attention, even though its deleterious effect has been largely proved. Alternating sitting and non-sitting at work, as well as an extra 15 to 30 min/day of LTPA, can attenuate the harms of prolonged occupational sitting. Thus, emphasizing the associated harms and suggesting workplace system changes could help the society to de-normalize this common behavior, similarly to the process of de-normalizing smoking.