Many scientists and healthcare professionals describe sitting as a scourge of modern health. However, this something that many people do both at work and leisure.
A previous study of nearly 6,000 people in the U.S. aged over 18 found that 1 in 4 people sat for more than 8 hours a day.
Published in JAMA and based on data collected in the National Health and Nutrition Examination Survey (NHANES) by the Centers for Disease Control and Prevention (CDC), the study found a mere 3% of respondents sat less than 4 hours a day and were active.
Now a new study, appearing in the Journal of the American Heart Association, has looked at the sitting habits of postmenopausal women with overweight and obesity. The women were aged about 55 and older.
In this observational study, the researchers analyzed the data as a single group. They also split it into two ethnic groups — Hispanic and one non-Hispanic — to see if total sitting time varied by group and how this impacted heart disease risk.
“Historically, heart disease in women has been understudied, despite this being the number one cause of death in women,” said lead author Dr. Dorothy Sears of Arizona State University College of Health Solutions in Phoenix, speaking to Medical News Today.
A third of women will die from heart disease
“1 in 3 women will die from heart disease,” said Sears. “Older women are the fastest-growing population in the U.S., and after menopause, [they] experience a dramatic increase in risk for cardiometabolic diseases, such as cardiovascular disease and type 2 diabetes.”
For this reason, it is critical to understand how behaviors impact this risk. Evidence is mounting that prolonged sitting is not only prevalent but linked to heart disease and mortality risks, especially in older adults.
“Thus, postmenopausal women [with overweight or obesity] who partake in prolonged sitting time likely have highly compounded cardiometabolic risk,” said Sears.
The study looked at 518 women with a mean age of 63 and an average body mass index (BMI) of 31 kilograms per meter squared (kg/m²). The classification of obesity is a BMI of over 30 kg/m².
The women wore a device that tracked their sitting and physical activity over 14 days and underwent a blood test to measure their blood sugar and insulin resistance.
Researchers found that, on average, the women who were not Hispanic sat for more than 9 hours a day, compared with an average of 8.5 hours a day by their Hispanic peers.
The researchers found links between prolonged sitting and greater BMI and waist measurements, as well as higher fasting blood sugar, insulin, triglycerides, and insulin resistance. All of these are factors in the risk of heart disease and stroke.
The strength of the findings surprised the researchers.
“I expected that there would be some association between sitting time and insulin resistance but did not expect such a strong magnitude of effect.” – Dorothy Sears
Researchers found that every additional hour of sitting time per day led to more than a 7% increase in insulin resistance, and each additional 15 minutes of uninterrupted sitting saw an almost 9% increase in insulin resistance, on average.
Not only that, but the magnitude of these links changed very little when researchers controlled the participants’ levels of exercise.
“Evidence from our study, and that of others, show that prolonged sitting time is a cardiometabolic health risk, independent of exercise,” said Sears.
“Clinicians and other healthcare providers should encourage [people] to reduce their sitting time, total daily sitting time, and uninterrupted bouts of sitting, in addition to encouraging exercise,” she said.
Other studies suggest that replacing sitting time with standing or light activity may promote health in older people.
“Accumulating evidence suggests that sitting time interruptions should be practiced throughout the day and need not be high intensity or long in duration.” – Dorothy Sears
The study also found that despite spending less total time sitting a day and for shorter uninterrupted periods, Hispanic women saw a more pronounced impact on blood glucose.
The results showed that for every additional 15 minutes of uninterrupted sitting, Hispanic women saw a 5% increase in fasting blood sugar levels compared to the other women in the study, who saw just a 1% increase.
However, Sears said researchers need to corroborate this finding with a more extensive multi-ethnic study.