Reduction of Sitting Time: Sedentarism Intervention Trial (SIT)

Evidence for the health benefits of regular physical activity is clear and unanimous. Recently, observational studies have found that prolonged bouts of sitting time are associated with chronic disease and mortality, even in individuals who engage in regular physical activity. These new findings indicate that sedentary behaviour should be regarded as a distinct class of behaviour with independent effects on disease risk, separate from the behaviour of leisure time physical activity. Prolonged daily sitting time is prevalent in modern, western society, making further exploration into this field of research a relevant public health issue.

It remains to be tested, whether it is possible to reduce sedentary leisure time in adults and whether a reduction of sedentary leisure time will lead to a decrease in biological CVD risk factors.

The investigators hypothesize that sedentary behaviour during leisure time and at work may be reduced through a theory-based individually tailored lifestyle intervention.

Aim: To examine whether an individually tailored lifestyle intervention aimed at reducing TV-viewing and other sedentary activities during leisure time and at work, can reduce sitting time, waist circumference, BMI and blood pressure; and improve serum lipid level.

Study population: From the "Health2010" study, that was initiated February 2010 at the RCPH, 150 sedentary participants will be consecutively invited and randomised by computer-generated random numbers into A) an intervention group (n=75) and B) a control group (n=75), when visiting the RCPH for the health examination. The entire Health2010 population will comprise 4.000 men and women between 19 and 69 years of age.

Control group: The control group will be instructed to maintain their usual lifestyle, including physical activity level and sedentary behaviour. After the intervention period is terminated, participants in the control group will be given the written material (booklets etc.).

Primary outcome measure: Time engaging in sedentary activities (hours & minutes per day), as measured by ActivPAL. Secondary outcome measures: self-reported physical activity and sitting time, total cholesterol, HDL, triglycerides, LDL, weight, waist circumference, systolic and diastolic blood pressure. Outcome measures will be obtained at baseline (inclusion) and after 6 months.

A possible effect of the intervention on self-reported sedentary leisure time (primary outcome) and biological CVD risk factors (secondary outcomes) will be explored by comparison of intervention and control group at baseline and follow-up. Regression analysis and intention-to-treat analysis will be applied and a significance level of 0.05 will be used.