Too Much Sitting Accelerates Aging, Dementia Risk

Scientists have linked extended bouts of sitting with increased risk of heart disease; certain types of cancers; pain and injury; early mortality; and more. Two new studies add to the long list of potential risks associated with sitting too long.

The first study, published in the American Journal of Epidemiology (2017; doi: https://doi.org/10.1093/aje/kww196), included 1,481 white and African-American women, average age 79. Its main focus was to examine associations between leukocyte telomere length—considered a strong indicator of aging—and sedentary time. People with shorter LTL tend to have shorter life spans and are deemed physiologically "older" than individuals with longer LTL.

Study variables included self-reported activity levels and actual activity measurements over 7 days, collected by an accelerometer worn on the hip. LTL data was gathered via DNA sample extraction. According to the results, women with the lowest activity levels were most likely to be white, older and obese.

"They were also more likely to have high blood pressure, a history of chronic diseases, a lower physical performance score . . . and to have experienced a fall in the past 12 months," said the authors.

The least active women had shorter LTL than women logging a higher number of active minutes per day. According to the researchers, the most
sedentary women were biologically 8 years older than their chronological age.

"Therefore, avoidance of a highly inactive lifestyle may provide health
benefits at the cellular level," advised the authors.

A second study looked at dementia risk in sedentary people with and without a genetic predisposition for the disease. The researchers, who tracked more than 1,600 older adults for 5 years, found that while carriers of the apolipoprotein E (APOE) genotype—a marker of dementia risk—had a higher likelihood of developing dementia than noncarriers, inactivity dramatically increased the risk for those without the gene.

"The important message here is that being inactive may completely negate the protective effects of a healthy set of genes," said study co-author Jennifer Heisz, PhD, an assistant professor in the department of kinesiology at McMaster University in Hamilton, Ontario. "Given that most individuals are not at genetic risk, physical exercise may be an effective prevention strategy."

This study was published in the Journal of Alzheimer's Disease (2017; 56 (1), 297—303).