"This is the first work to demonstrate that sedentary behavior might have a greater bearing on diabetes risk factors than exercise in adults at risk of the disease," said lead author Joseph Henson, a PhD student from the Leicester Diabetes Center, United Kingdom.
Mr. Henson stressed, however, that sedentary behavior "is not simply a lack of exercise," and trying to reduce it "shouldn't be used as a substitute for exercise; they should be treated independently.
"This requires a paradigm shift, so that people at high risk of developing type 2 diabetes think about the balance of sedentary behavior and physical activity throughout the day," he added, noting that sedentary time occupies a much larger portion of the day than time spent in physical activity.
Sedentary Time Affects Glucose, TGs, and HDL Cholesterol
In their study, Mr. Henson and colleagues analyzed individuals with known risk factors for type 2 diabetes from 2 ongoing diabetes-prevention programs in the UK: 153 from the Sedentary Time and Diabetes (STAND) study (mean age, 33 years; 29% men) and 725 from the Walking Away from Diabetes study (mean age, 64 years; 65% men).
They examined the extent to which sedentary time, breaks in sedentary time, MVPA, and total physical activity were independently associated with cardiometabolic risk factors. Accelerometers were used to assess sedentary time, MVPA, and total physical activity. Breaks in sedentary time were defined as a transition from a sedentary to an active state.
Following adjustment for various covariates, including MVPA and body mass index (BMI), there were detrimental linear associations of sedentary time with 2-hour plasma glucose (P < .001), triglycerides (P= .001), and HDL cholesterol (P = .029).
Breaks in sedentary time, total physical activity, and MVPA were significantly inversely associated with measures of adiposity, but not with any other cardiometabolic variables after adjustment for sedentary time and BMI.
The findings were consistent across a diverse age range, providing evidence that the negative consequences of excess sedentary time exist from young adulthood through older ages (ages 18 to 74 years), another unique aspect of the study, said Mr. Henson. He noted that previous studies that have shown detrimental effects of sedentary behavior have been performed in older adults in the general population.
"The findings from this study may have important methodological and public-health implications," he and his colleagues point out. "This…provides novel objective evidence that, in individuals at high risk of type 2 diabetes mellitus, sedentary time may be a more important indicator of cardiometabolic health than MVPA."
Diabetes Prevention Should not Overlook Sedentary Time
The results also have implications for diabetes and cardiovascular disease prevention programs, they say.
"This may raise questions regarding the prescription of optimal daily human movement for health. As such, diabetes and cardiovascular [disease] prevention programs concentrating solely on MVPA may overlook an area that is of fundamental importance to cardiometabolic health.
"Along with messages related to accumulating at least 150 min/week of MVPA, which forms the cornerstone of diabetes-prevention programs, such interventions may be more effective if individuals are further encouraged to simply sit less and move more, regardless of the intensity level," they add.
Future Study Will Try to Tease out Biological Mechanism
Mr. Henson stresses nevertheless that the research "is still only a cross-sectional, observational study," which should serve as a stimulus for further work, including tightly controlled experimental studies in different populations.
To this end, he and his colleagues plan to conduct another study, assessing individuals at risk of diabetes who will be assigned to 1 of 3 groups: sitting all day, walking about for 5-minute intervals twice an hour, and standing for 5-minute intervals twice an hour. They plan to try to tease out the biological mechanisms that are at play, Mr. Henson explained.
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