Health Letter, January 2014
We often hear about the myriad benefits associated with physical exercise.
But today, many people work in offices and spend their free time sitting in front of televisions, computers or other electronic devices. New information is now emerging regarding the detrimental health effects of spending too much time just sitting still.
Benefits of an active lifestyle
The first U.S. Surgeon General report to focus on the importance of physical activity came in 1996. Entitled “Physical Activity and Health: A Report of the Surgeon General,” it emphasized the health benefits offered by regular, moderate exercise. This was followed by an update from the U.S. Department of Health and Human Services (HHS) in 2008, entitled “Physical Activity Guidelines for Americans,” encouraging people of all ages to get involved in physical activity. The HHS report stated the following major research findings:
- Regular physical activity reduces the risk of many adverse health outcomes.
- Some physical activity is better than none.
- For most health outcomes, additional benefits occur as the amount of physical activity increases through higher intensity, greater frequency, and/or longer duration.
- Most health benefits occur with at least 150 minutes (2 hours and 30 minutes) a week of moderate-intensity physical activity, such as brisk walking. Additional benefits occur with more physical activity.
- Both aerobic (endurance) and muscle-strengthening (resistance) physical activity are beneficial.
- Health benefits occur for children and adolescents, young and middle-aged adults, older adults, and those in every studied racial and ethnic group.
Risks of being sedentary
Many people now spend much of their time watching television or engaging in other screen-based entertainment, sitting while commuting, and sitting at a computer, which begs the question: What are the health effects of a sedentary lifestyle?
Researchers have linked the amount of time one spends sitting each day to the risk for type 2 diabetes, as well as death from any cause and death specifically related to cardiovascular disease.
A paper published March 2012 in the Archives of Internal Medicine focused on 222,497 individuals in the “45 and Up Study,” an ongoing study of people 45 years old and older living in New South Wales, Australia. These individuals were all enrolled in the Medicare Australia system, a database that includes all Australian citizens and permanent residents. Researchers sent questionnaires to a random sample of 45 and Up Study participants, with one version for women and another for men. Those completing the forms and mailing them back represented approximately 11 percent of the entire New South Wales population in that age group.
The questionnaires were quite extensive. Individuals were asked to use the Active Australia Survey to document their physical activity and provide information on possible confounding factors such as sex, age, educational level, urban/rural residence and body mass index that can impact health status. The researchers tabulated the number of deaths that occurred after an average of 2.8 years. To determine mortality, researchers used the New South Wales Registry of Births, Deaths, and Marriages from February 2006 through December 2010.
The main question posed was, “About how many hours in each 24-hour day do you usually spend sitting?” To quantitate the amount of time an individual spent sitting, the researchers defined four categories: zero to less than four hours per day, four to less than eight hours per day, eight to less than 11 hours per day, and 11 or more hours per day. “Sitting time” in this study referred to sedentary activities, or time spent sitting (and not, in this case, lying down and sleeping).
To analyze physical activity, the researchers again defined four categories: no physical activity (zero minutes per week), some physical activity (one to 149 minutes per week), an amount of physical activity meeting the minimum recommended by the World Health Organization (WHO) (150-299 minutes per week), and an amount of physical activity meeting at least twice the WHO minimum (300 minutes or more per week).
After making adjustments to take into account possible confounding factors (that is, to remove the influences of age, sex, urban or rural setting, etc., on sitting times), the researchers found that all-cause mortality (death from any cause) rose with an increase in time individuals spent sitting.
When looking at the data for all individuals in all categories combined, researchers found that an 11 percent increase in mortality accompanied each increase in sitting-time category. Factoring in the physical activity categories, researchers also found that the mortality rate was highest among those who were the least physically active and who sat the longest times.
The researchers compared all-cause mortality of those who were healthy when the study began with those who had cardiovascular disease or diabetes when the study began. As expected, mortality rates were higher (by about fourfold) in those who had heart disease or diabetes at baseline versus those who were healthy at baseline. For the unhealthy group, those who sat the most (more than 11 hours per day) generally had higher mortality rates than those who sat for less than 11 hours per day, even if they exercised.
Encouragingly, other researchers have defined a category of activity between sitting and exercise that likely offers health benefits. This category, which the researchers called “light activity,” includes activities such as “slow walking, sitting and writing, cooking food and washing dishes.” Using an electronic device called an accelerometer to monitor activity throughout the day, the researchers in one study estimated that it was possible to achieve similar total energy expenditures either through a short burst of vigorous activity or a much longer period of light activity.
Another, similar type of study, also using the accelerometer, demonstrated a variety of activity patterns in individuals and found that having many periods of light activity throughout the day (including standing and incidental walking) could have many benefits, such as weight control, that are currently attributed to more vigorous exercise. The researchers in this study hope that physicians will tell their patients that for health benefits, they “need to get out of their chairs more frequently, both at work and at home.”
The take-home messages provided by these studies are clear. It is important not only to engage in moderate to vigorous physical activity but also to avoid sitting for long periods of time. Being engaged in light physical activity throughout the day is certainly helpful. The bottom line would appear to be “keep moving.” Any activity is healthier than passive sitting.