People are sitting more than ever, and few pay attention to how they sit throughout the day.
Some of the most common sitting activities include eating meals; driving; talking on the phone; using a computer, television, or small device; and reading.
Scientists have found that sitting for too many hours per day, or sitting for long periods without a break, could increase a wide range of health risks.
This is true even if you engage in recommended amounts of physical activity.
Several recent studies have shown that too much sitting could harm your heart, brain, and may increase your cancer risk.
Sitting too long could hurt your heart
One study from Johns Hopkins University School of Medicine found that as little as six years without physical activity and sitting too long every day in middle age is linked to an increased risk of heart failure.
Conversely, middle-aged people who bump their weekly exercise up to recommended levels over six years may strongly decrease their risk of heart failure.
Unlike a heart attack, in which heart muscle dies, heart failure involves a long-term chronic inability of the heart to pump enough blood hard enough to bring needed oxygen around the body.
The condition affects an estimated 5 million to 6 million Americans. It is the leading cause of hospitalization in those over 65.
Heart failure risk factors include high blood pressure, high cholesterol, diabetes, smoking, and a family history.
In the study, the researchers analyzed self-reported physical activity levels over time in more than 11,000 American adults.
The data were from the federally funded long-term Atherosclerosis Risk in Communities (AIRC) study.
The participants were recruited from 1987 to 1989 in Forsyth County, North Carolina; Jackson, Mississippi; greater Minneapolis; and Washington County, Maryland.
Each participant rated his or her physical activity as poor, intermediate, or “recommended,” in alignment with guidelines issued by the American Heart Association.
The team found those with recommended activity levels at both the first and third visits during the study showed the most heart failure risk decrease, at 31% compared with those with consistently poor activity levels.
In addition, heart failure risk decreased by 12% in the 2,702 participants who increased their physical activity from poor to intermediate or recommended, or from intermediate to recommended.
On the other hand, heart failure risk increased by 18 percent in the 2,530 participants who reported decreased physical activity.
The researchers suggest that consistently participating in the recommended 150 minutes of moderate to vigorous activity each week… in middle age may be enough to reduce your heart failure risk by 31%.
In another study, researchers at UT Southwestern Medical Center have found that sedentary behavior like sitting too long is linked to increased amounts of calcium deposits in heart arteries.
This, in turn, is associated with a higher risk of heart attack.
Previously, the team has shown that excessive sitting is associated with reduced cardiorespiratory fitness and a higher risk of heart disease.
In this study, the researchers asked some 2,000 participants in the Dallas Heart Study to wear a device that measured their activity levels for a week.
The participants spent an average of 5.1 hours sitting per day and an average of 29 minutes in moderate to vigorous physical activity each day.
The researchers observed a strong association between increased sedentary time and coronary artery calcium.
Specifically, each additional hour of daily sitting time is linked to a 12% higher likelihood of coronary artery calcification.
Therefore, reducing daily “sitting time” by even 1 to 2 hours per day could have a significant and positive impact on future cardiovascular health.
The finding is published in the Journal of the American College of Cardiology: Cardiovascular Imaging.
Sitting too long could harm your brain
A recent UCLA study found that sitting too long is linked to changes in a section of the brain that is critical for memory in middle-aged and older adults.
In the study, the team recruited 35 people ages 45 to 75 and asked about their physical activity levels and the average number of hours per day they spent sitting over the previous week.
Each person had a high-resolution MRI scan. It provides a detailed look at the medial temporal lobe, or MTL, a brain region involved in the formation of new memories.
The researchers found that sitting too long is a big predictor of thinning of the MTL and that physical activity, even at high levels, is insufficient to offset the harmful effects of sitting for extended periods.
MTL thinning can be a precursor to cognitive decline and dementia in middle-aged and older adults.
In another study from the University of Western Australia, researchers examined the prolonged negative impact that sitting might have on our brains.
They found sitting for long periods throughout the day alters blood glucose levels, which in turn may affect the brain.
The brain is a powerful organ but it needs a stable glucose supply to function optimally.
The brain weighs about 2% of our body mass but demands about 20% of our resting energy requirements, which is mostly in the form of glucose.
Glucose levels outside that optimal range (caused by sitting too long) can have a negative impact on brain health.
Multiple studies had demonstrated that reducing and replacing sitting with light intensity walking helps keep glucose levels in the optimal range, particularly after food consumption.
This means glucose levels do not spike too high or dip too low.
Sitting too long may dramatically increase death risk from cancer
In a study from Roswell Park Comprehensive Cancer Center, researchers found a link between physical inactivity and an increased risk of mortality among cancer patients.
Previous studies have shown a strong link between lifetime inactivity and increased risk of particular cancers.
This research demonstrates an association of pre- and post-diagnosis inactivity with survival across several different cancer types.
Cancer patients often face unique exercise challenges due to their disease and its treatment.
In the study, the research team examined the association between habitual physical inactivity and outcomes in 5,807 cancer patients enrolled in the Data Bank and BioRepository (DBBR) at Roswell Park between 2003 and 2016.
The team looked at patterns of physical activity over time, during a period spanning the decade before the cancer was diagnosed and continuing for up to one year after diagnosis.
Cancer patients who engaged in regular, moderate- to vigorous-intensity physical activity (such as walking, running, aerobics or other cardiovascular exercises) both before and after their diagnosis were considered habitually active.
But those who did not exercise regularly were considered habitually inactive.
The researchers found that patients who were physically active both before and after treatment were 40% more likely to survive than those who were physically inactive.
Moreover, this was true for many different disease types, including breast, colon, prostate, ovarian, bladder, endometrial, esophageal and skin cancer.
The researchers suggest that when it comes to exercise, something is better than nothing but regular, weekly exercise seems to really make a difference.
Patients who were physically active three or four days a week experienced an even greater benefit than those who exercised daily.
The finding was presented at the American Association for Cancer Research (AACR) Annual Meeting 2018 in Chicago, Ill.
Sitting too long could also bring other health risks
Researchers from USC reveal that many people have moderate to severe lower back pain just because they’re sitting down all the time.
Over time, the muscles that attach the hips to the lower back become very tight, and the deep trunk muscles become weak.
Due to the imbalance, they start having issues at different lumbar sections of the lower back.
A recent study from UCSD, UCSF, and University of Newcastle found that sitting too long might contribute to diabetes.
When people sit for long periods without getting up, the large weight-bearing muscles of the legs remain dormant.
With no action, these muscles are unable to efficiently use the sugars and fats that float around in your blood—and in theory, this could lead to weight gain and metabolic diseases such as diabetes.
At the same time, reduced blood flow in your arteries leads to hostile conditions that promote injury to the blood vessel walls.
Furthermore, when the leg muscles remain shut off for long periods, blood collects in veins which leads to an increased risk for blood clots, or deep venous thrombosis.
Previous research has shown that people with prolonged sitting patterns had larger waistlines, higher BMI, and in their blood had less good fats, more bad fats, and higher levels of blood sugar.
Prolonged sitting patterns make the body not be able to metabolize fats or sugar, and they can increase blood pressure and fatigue.
In the study, the team recruited over 6,000 women aged 65-99 from the Women’s Health Initiative and measured their sedentary patterns for seven days using research-grade activity monitors.
They also examined over 20 years of detailed health records, which included information on whether the women had ever been diagnosed by a physician with diabetes.
They found the group with the most prolonged sedentary patterns had the most women with diabetes. The group with the most interrupted patterns had the fewest women with diabetes.
Another study from the Netherlands studied 2,500 adults ages 40-75 and found that prolonged sitting patterns were associated with Type 2 diabetes and with metabolic syndrome.
The researchers suggest sitting patterns may contribute to the growing international diabetes epidemic.
There is a possibility that changing the sitting patterns might provide protection against diabetes, especially if long sitting bouts were always broken with light activity or even better, moderate-intensity activity, as recommended by the American Diabetes Association.
A third study shows that women who spend more time sitting down as they age are at higher risk of becoming frail.
The researchers from the University of Queensland looked into the sitting patterns of almost 5,500 middle-aged Australian women over a 12 year period.
They found women who had high levels of sitting – about 10 hours a day—were more at risk of becoming frail.
They classed 5.5 hours sitting per day as a medium level of sitting, while 3.5 hours per day represented a low level.
They suggest women should try and limit their sitting time to low or medium levels, as well as being physically active.
The finding is published in the American Journal of Epidemiology and used data from the Australian Longitudinal Study of Women’s Health.
How to save your health from sitting too long
One study from the University of Otago suggests getting off your bum and move around for two minutes every half hour.
The team reviewed 44 international studies which evaluated the acute metabolic and vascular impact of interrupting prolonged sitting.
They found that compared to prolonged sitting, performing short, regularly repeated bouts of activity lowered the concentrations of blood sugar and insulin in the bloodstream for up to nine hours after a meal.
The concentrations of fat in the blood can also be lowered, although this effect seems to be delayed, only occurring 12 – 16 hours after the activity has been initiated.
The most interesting finding is that the magnitude of the reductions in blood sugar, insulin or fat doesn’t seem to be affected by the intensity of the activity performed, what you have eaten, how old you are, or how much you weigh.
This means the current physical activity guidelines to sit less and move more could apply to everyone.
People should find all ways to avoid sitting for long periods and to increase the amount of movement we do throughout the entire day.
The study is published in Sports Medicine.
Copyright © 2019 Knowridge Science Report. All rights reserved.
Source: University of Otago, UCLA, UT Southwestern Medical Center, Johns Hopkins University, University of Western Australia, Roswell Park Comprehensive Cancer Center, USC, The Conversation, University of Queensland.