More Evidence That Sitting Too Much Is Bad, Ups Diabetes Risk

Veronica Hackethal, MD

February 03, 2016

Another new study indicates that too much time spent in sedentary activities, like working on a computer and watching TV, isn't good for the health. According to this latest research, it could increase the risk of type 2 diabetes and metabolic syndrome.

"Our results demonstrate that each extra hour of sitting time per day is associated with a 22% increased odds for type 2 diabetes. These results are independent of high-intensity physical activity, like exercise," commented first author Julianne van der Berg, a PhD candidate in social medicine at Maastricht University, the Netherlands. She and her colleagues published their work online February 2 in Diabetologia.

Prior research has suggested that spending extended periods of time sitting down, either at work or during leisure time, is detrimental and contributes to mortality risk regardless of how much physical activity an individual undertakes. Sitting has even been dubbed "the new smoking."

This new study used a device called the activPAL (PAL Technologies) to monitor sedentary behavior and is the first to look at links between objectively measured sedentary behavior and type 2 diabetes.

It also examined patterns of behavior: breaks (how often sedentary time is interrupted) and sedentary bouts (the length of uninterrupted sitting time).

As a new area of research, only a few observational studies have looked at sedentary breaks, according to Ms van der Berg. Experimental studies, though, have suggested that breaking up sitting time could benefit health, but these looked at different study populations and only evaluated short-term effects, she explained.

Sedentary Time, Breaks, and Bouts Measured

There were 2497 participants (mean age 60 years, 52% men) in The Maastricht Study, a prospective cohort study from the Netherlands focusing on factors related to the development, complications, and comorbidities of type 2 diabetes, included in the current analysis.

To monitor their sedentary behavior — defined as any waking behavior characterized by an energy expenditure ≤ 1.5 metabolic equivalents while in a sitting or reclining posture — participants wore the activPAL on their thigh for 24 hours per day for 8 days in a row. ActivPAL measures sedentary behavior using posture and has previously been shown to accurately monitor this.

Researchers used a 75-g oral glucose tolerance test to measure blood glucose levels. They used WHO criteria to evaluate glucose metabolism and the Adult Treatment Panel (ATP) III guidelines to assess metabolic syndrome.

Participants self-reported education level, smoking, alcohol consumption, mobility limitations, health status, and diabetes duration.

Researchers did interviews to obtain medication information and physical exam and lab testing for body mass index (BMI) and HbA1c.

Results showed that 55.9% (n = 1395) of participants had normal glucose metabolism, 15.5% (n = 388) had impaired glucose metabolism, and 28.6% (n = 714) had type 2 diabetes.

Participants with type 2 diabetes had logged the greatest amount of sedentary time — up to 26 minutes more per day than either those with normal or impaired glucose metabolism.

After adjustment for 11 factors potentially linked to metabolic dysfunction, including high-intensity physical activity and BMI, results showed that each additional hour spent sedentary raised the risk of type 2 diabetes by 22% (odds ratio [OR], 1.22) and the risk of metabolic syndrome by 39% (OR, 1.39).

The pattern of sedentary time (number of breaks, prolonged sedentary bouts defined as 30 minutes or more, and average bout duration) showed no significant association with either glucose metabolism status or risk of metabolic syndrome.

Largest Study to Use Accelerometry, but Limitations

"To our knowledge, our study is the largest in which posture-discriminating accelerometry was used to objectively measure total amount and patterns of sedentary behavior in a sample of adults comprising participants with type 2 diabetes or impaired or normal glucose metabolism," say the researchers.

The cross-sectional nature of the study limits evaluation of cause and effect, however, they note.

For example, people with type 2 diabetes might have spent more time sitting because of poor health. Excluding patients on insulin, which may indicate more severe disease and worse health, did not change the results.

In addition, the study monitored sedentary behavior for just 1 week, which may not have been long enough to capture the true habits of the participants.

Nevertheless, the results still indicate that reducing the total amount of time spent sitting each day could bring health benefits, says Ms van der Berg.

"This may be achieved by replacing short periods of sitting time by standing time or stepping time, like standing up during commercial breaks while watching TV, standing or walking during phone calls, or walking during a lunch break or after dinner."

Further studies are needed, she added, that look at the effects of sedentary breaks in people of different ages and with various metabolic profiles, as well as the short- and long-term health effects of breaks.

The authors report no relevant financial relationships.

Diabetologia. Published online February 2, 2016.Article

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