Niha Zubair, Arivale Clinical Research Scientist, PhD
Modern society has given us many reasons not to move: smartphones, TVs, and computers chief among them. And, it’s not just our jobs forcing us to be behind a screen or at a desk; studies find the majority of our hours outside work are spent sitting.
That can be bad news for our health. Numerous studies have shown prolonged time spent sitting is associated with increased all-cause mortality (risk of death from any cause) and increased risk of diseases, including type 2 diabetes, cardiovascular disease, and some cancers. Furthermore, these risks seem to be independent of physical activity. In other words, exercising doesn’t seem to negate the risks associated with excessive amounts of sitting.
Now, a study published last month in the American Journal of Epidemiology and covered by NBC News reports a significantly higher risk of death from cancer, heart disease, diabetes, suicide, and more for people sitting over six hours per day outside of work.
While the risks of sitting have been studied, less is known about the specific causes of death associated with spending time at your desk or on the couch.
With this new study, researchers from the American Cancer Society sought to further examine the associations between sitting time and the risk of specific causes of death using a large prospective U.S. cohort study of over 127,000 men and women.
At the beginning of the study, participants – between the ages of 50 to 74 years – were free of any major chronic diseases and were asked a question about the number of hours they spent sitting – outside of work – every day. After about 21 years of follow-up, over 48,000 participants had died.
Leisure-time sitting for over six hours per day was associated with a 19-percent higher all-cause death rate compared to individuals who reported sitting under three hours per day.
Risk was significantly higher for 14 of the 22 specific causes of death examined, including deaths from cancer, coronary heart disease, stroke, diabetes, kidney disease, suicide, COPD, pneumonitis, liver disease, digestive disease, Parkinson’s disease, Alzheimer’s disease, nervous disorders, and musculoskeletal disorders. Notably, eight of the top 10 leading causes of death in the United States are included in this list.
These results accounted for factors that may influence both mortality and sitting behavior, such as physical activity, BMI, smoking behavior, alcohol consumption, education level, and occupation status.
The researchers propose three possible reasons for the association between excessive sitting and increased risk of death.
First, and most obvious, time spent sitting means less time spent being physically active. However, the researchers accounted for moderate to vigorous physical activity and found that the results remained the same.
Second, sedentary activities are commonly associated with other unhealthy behaviors, such as increased snacking, which could lead to excess weight gain and thus an elevated risk of disease-related death.
Lastly, prolonged time spent sitting has been shown to have detrimental metabolic consequences, especially on cardiometabolic factors – such as lipids, blood sugar, and blood pressure – and systemic inflammation.
Regardless of the possible reasons mentioned above, these results – along with the results from many other observational studies – suggest that reducing time spent sitting could help prevent death and disease.
But, there are some limitations to the study as noted by the researchers.
First, while participants at the beginning of the study were free from some major chronic diseases – including cancer, heart attack, stroke, and lung disease – researchers lacked information on other diseases. This means participants may have had a disease, other than those mentioned, at the beginning of the study that predisposed them to a higher risk of death. Furthermore, these diseased individuals could have been more sedentary due to the nature of their disease. Without accounting for the disease, one would conclude that for these individuals sedentary behavior was linked to a higher risk of death, but in actuality the underlying disease may have caused the death.
Next, researchers didn’t have information on objective physical activity information; it was self-reported. In addition, they didn’t have data on occupational physical activity.
Lastly, researchers couldn’t differentiate among types of leisure-time sitting, such as TV watching and reading.
Despite these limitations, there’s a magnitude of evidence that for the average healthy individual too much time spent sitting is harmful for health. More studies are needed to better understand how reductions in sitting time affect health outcomes. This could eventually lead to public health guidelines on appropriate amounts of sitting time akin to what we currently have for physical activity.
In the meantime, here are three easy tips for reducing your time spent sitting:
- Walk while talking on the phone or before dinner.
- Set an alarm on your phone to take a quick two-minute walk every 30 minutes.
- Take frequent breaks from sitting – get up to get a cup of water or tea, for example.
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[Arivale Hot Topics address health stories currently in the news. The Arivale Clinical Team’s commentary on these news articles is not a review of the scientific evidence, nor an endorsement of a specific study, and is not meant as official medical opinion.]