Turn Off TV: Less Sitting, Less Diabetes in At-Risk Patients

Becky McCall

April 02, 2015

Less time spent sitting lowers the chance of developing type 2 diabetes in individuals at high risk of the disease, according to a new study based on data from the Diabetes Prevention Program (DPP). The authors emphasize that sitting behavior may be an additional modifiable risk factor for diabetes that could have public-health implications.

"Our results showed that for every hour spent watching television there was a 3.4% increased risk of developing diabetes during the 3-year follow-up in individuals who were at high risk of developing the disease. This was true even after controlling for the effects of physical activity on diabetes incidence," said lead researcher Bonny Rockette-Wagner, PhD, director of physical-activity assessment at the University of Pittsburgh, Pennsylvania.

Published online April 1 in Diabetologia, the study examined whether sedentary time spent watching television, as well as sitting at work, was influenced by the DPP lifestyle intervention, which had the goals of increasing moderate-intensity physical activity and decreasing weight. The researchers also looked at the effect of sedentary time on the development of type 2 diabetes.

"Our finding of a relationship between sedentary behavior and diabetes incidence suggests that reductions in sitting can translate into a positive health effect separate from improvements to moderate-vigorous activity," Dr Rockette-Wagner continued.

Effect of Sedentary Time Is Important

To date, most lifestyle interventions designed to decrease diabetes risk have focused on weight loss, dietary changes, and increasing physical activity but have not examined the contribution of sedentary time or sitting behavior, Dr Rockette-Wagner pointed out.

In light of this, the new analysis aimed to determine whether the DPP lifestyle intervention reduced sedentary behavior despite the lack of a specific program goal to reduce sitting. "We also wanted to see if sedentary behavior was related to diabetes incidence," she added.

Data on 3234 overweight US adults enrolled in the DPP were used in the analysis. Participants were at least 25 years of age and had prediabetes at the start of the DPP.

The multicenter DPP was designed to determine whether metformin or lifestyle intervention could prevent or delay type 2 diabetes in high-risk adults. Patients received placebo, metformin, or lifestyle intervention (150 min/week of moderate-intensity activity and 7% weight loss).

Dr Rockette-Wagner explained that for their study the DPP also collected data on television watching and sitting at work throughout the study period (mean, 3.2 years).

Level of sedentary behavior was collected at baseline and annually using an interviewer-administered Modifiable Activity Questionnaire, and findings were reported as time spent watching television or combined with sitting at work.

The mean change in sedentary time was assessed over the study period, and the relationship between sedentary time and diabetes incidence was determined.

Lifestyle Intervention Reduced Television Watching

At baseline, mean time watching television was not significantly different between the placebo (144 min/day), metformin (139 min/day), and lifestyle-intervention (144 min/day) groups.

Dr Rockette-Wagner reported that individuals in the lifestyle-intervention group reduced television watching by a mean of 22 min/day and the combination of television watching and sitting at work by a mean of 37 min/day.

Those in the metformin and placebo groups reduced television watching by a mean of 3 and 8 min/day, respectively, and combined television watching and sitting at work by 6 and 9 min/day, respectively.

The reduction in television watching in the lifestyle arm "was significantly greater than any changes seen in the other randomized groups that did not receive the lifestyle intervention,” she said, adding that there was a relationship between incidence of type 2 diabetes and television watching in all three treatment groups.

The effect of television watching on diabetes incidence remained even after researchers controlled for any effects of physical activity on diabetes incidence.

The authors also note that this association was reduced when time-dependent weight was added to the model (to a 2.1% increased risk of developing diabetes per hour of watching television, which was not significant), suggesting that subsequent changes in body weight may account for some of the relationship between sitting behavior changes and diabetes development.

"The attenuation points to weight as an important factor in diabetes development," said Dr Rockette-Wagner, who noted that previous studies have shown that more time sitting is related to greater weight and weight gain. "Therefore, sedentary behavior could also play a role in the effect of weight on diabetes development."

Dr Rockette-Wagner also highlighted that a recent review suggested that improving physical activity through lifestyle intervention might not necessarily have a similarly beneficial effect on sedentary time (Am J Prev Med. 2015;41:189–196).

But by contrast, the results of this study showed that an intervention known to improve moderately intense activity did positively affect sedentary time despite a lack of emphasis on decreasing sedentary behavior.

Future Work

Dr Rockette-Wagner stressed that "the real issue is the lack of movement, not the sitting time watching television per se, and therefore we would expect to see a greater effect of sedentary time on diabetes incidence if we had a count of all minutes of sedentary [time] during the day."

She suggested that future studies could add to these results by examining whether total sedentary time, which can now be captured using objective electronic-activity monitors, has the same effect on diabetes incidence as specific self-reported sitting activities, like watching television.

"Using an activity monitor can provide a better assessment of total activity and sedentary behavior," she noted.

Finally, given that sedentary goals were not formally part of the DPP, Dr Rockette-Wagner emphasized the importance of investigating outcomes when sedentary goals are added to lifestyle interventions that focus on increasing physical activity and reducing weight.

The research team, led by Dr Rockette-Wagner's colleague, Andrea Kriska, PhD, University of Pittsburgh, has received a $3 million grant from the National Institutes of Health to test the efficacy of a community-based lifestyle intervention program in sedentary, overweight adults with prediabetes or metabolic syndrome that focuses on sitting less.

"The study involves modifying our existing, highly successful translation of the DPP — the Group Lifestyle Balance Program — by reducing the amount of time spent sitting rather than starting with an emphasis on increasing the amount of time [participants] spend exercising."

Dr Rockette-Wagner has declared no relevant financial relationships. Disclosures for the coauthors are listed in the article.

Diabetologia. Published online April 1, 2015. Article

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