Occupational sitting
Back in the 1950s, British researchers found that workers who spent a lot of time sitting (London bus drivers and mail sorters) had higher rates of cardiovascular disease compared to workers who stood and walked (bus ticket collectors and postal workers). In 2010, researchers conducted a systematic review of 43 studies that investigated links between sedentary occupational work and risks of health problems. Analysis of these studies revealed only weak evidence that higher amounts of occupational sitting predicts increased health risks including higher body-mass index, cardiovascular disease, diabetes, and mortality. Differences in study design and inconsistent measures of sitting, and failure of most studies to control for physical activity diminished the quality of the evidence.
More recent, better evidence
UK and Australian researchers addressed the deficiencies identified in previous studies of possible health risks of sitting occupations. The newer research used data from 5,380 women and 5,788 men in five cohorts in the Health Survey for England and the Scottish Health Survey. After accounting for confounding factors, including levels of leisure-time physical activity, women participants with a standing or walking occupation had significant 32 and 40 percent lower risks of dying of any cause or dying of cancer, respectively, compared to participants with sitting occupations during a median follow-up of 13 years. No significant differences appeared for men participants.
Analysis of occupation type and level of leisure-time physical activity together showed that the risks of dying of any cause were significantly 53 and 26 percent lower for women and men, respectively, for participants with non-sitting occupations and with high leisure-time physical activity. The comparable drop in cancer mortality risk was 58 percent for women (but not men). Thus, women seemed to benefit more from non-sitting occupations than men.
Less sitting at work may reduce your risk of cancer
Japanese workers sit for relatively long amounts of time. Japanese researchers used data for 33,307 participants in the Japan Public Health Center-based Prospective study to determine if longer amounts of occupation sitting predicted lower risk of various types of cancer for men and women.
After adjusting for confounding factors, including moderate to vigorous physical activity, and compared to men participants with 1-3 hours of daily occupational sitting time, men participants with 7 or more hours of daily sitting had a significant 125 percent higher risk of developing pancreatic cancer during an average follow-up of 10 years. For women participants, a similar comparable comparison showed a significant 180 percent increase in lung cancer risk. For both man and women, other types of cancer were not significantly related to increased occupational sitting. The non-significant results may have arisen, at least in part, due to low numbers of many types of cancers. No one wants pancreatic or lung cancer so why not find ways to reduce your daily sitting at work?
A new study
Many studies show that prolonged sitting, including occupational sitting, predicts adverse outcomes such as increased risk of cardiovascular disease and dying. However, results are inconsistent. A new study sheds some light on this matter. Researchers used data from 481,688 participants with an average of 39 years in a health surveillance program in Taiwan. Based on self-reports, daily occupational sitting was classified as 1) mostly sitting, or 2) alternating sitting and nonsitting, or 3) mostly nonsitting.
After an average follow-up of 13 years and after adjusting for confounding factors, participants who mostly sat at work had significant 16 and 34 percent higher risks of all-cause and cardiovascular mortality, respectively, compared to participants who mostly didn’t sit at work. Participants who alternated sitting and nonsitting at work did not have higher risks of mortality. Furthermore, participants who mostly sat at work and who reported low levels (15-29 minutes per day) of leisure time physical activity reduced their risk of all-cause mortality similar to that of physically inactive participants. You might reduce adverse health risks linked to sitting if you ramp up your leisure time physical activity even if you mostly sit at work.
What about neck, shoulder, and lower-back pain?
Musculoskeletal complaints (MSCs) account for a sizeable proportion of disability in developed countries. The World Health Organization calls MSCs an occupation epidemic. Disability may arise from ergonomically unhealthy postures and positions of modern office workers. A new report from Germany used data from 2,082 participants the Study of Mental Health in the Workplace to determine if sitting at work predicted increased risk of MSCs. The average men and women office workers reported sitting 43 and 32 hours per week, respectively.
Contrary to expectations, higher levels of weekly sitting at work at baseline did not predict increased risk of MSCs a year later. However, for workers who reported getting no leisure time physical activity, 25-35 hours per week of occupational sitting (but curiously not more than 35 hours per week) predicted greater prevalence of neck, shoulder, and lower back complaints after one year. Thus, the relationship between occupations sitting and MSCs seems to be affected by the amount of physical activity away from work.
Can workplace interventions reduce occupational sitting?
A recent systematic review of 34 studies from high-income countries concluded with workplace interventions might help reduce adverse health risks. The review considered physical workplace changes, workplace policy changes, information and counseling, and multi-component interventions. Low-quality evidence suggested that sit-stand desks can reduce workplace sitting at short and medium periods of time. Effects over long periods of time are unknown. Effects of other types of interventions were inconsistent. This study doesn’t say that interventions don’t work; rather the evidence is spotty and of low quality.
What to do
Breaking up prolonged periods of occupational sitting might reduce your risk of adverse health effects. Wearable devices can remind you to take periodic breaks. Perhaps you could recruit a co-worked to take short mid-morning and mid-afternoon walk breaks during work.
