Out of the 1,367 people in the total analyzed sample, 665 (48.6%) participants met the criteria for having metabolic syndrome. As shown in , participants with metabolic syndrome were more often women (P < 0.01), had a lower educational level (P < 0.01), were more often nondrinkers (P < 0.01), had a higher BMI (P < 0.001), had a higher prevalence of diabetes and heart disease, spent less time in the moderate-to-vigorous activity range, and had a lower average accelerometry count during active minutes in the day (P < 0.01).
Baseline characteristics of the study population
On average, people spent 9.5 h (65% of wear time) as sedentary. The correlation between total sedentary time and percent sedentary time was high (correlation coefficient 0.75); the correlation between total sedentary time with average length of a sedentary bout, intensity during sedentary time, and number of sedentary breaks was lower (correlation coefficients 0.55, −0.53, and 0.09, respectively). shows the age- and sex-adjusted means of the five sedentary variables according to each metabolic syndrome component and metabolic syndrome. Participants with a large waist circumference, low HDL cholesterol, high triglycerides, and metabolic syndrome had a higher percentage of sedentary time out of total wear time, a longer average sedentary bout, a lower average intensity during sedentary time (not statistically significant for HDL), and fewer breaks in sedentary time (all P < 0.05) after adjusting for age and sex.
Adjusted means* (SE) of five sedentary variables according to metabolic syndrome
shows the age- and sex-adjusted mean values of the five sedentary variables according to the number of metabolic syndrome criteria. A significant positive trend with the number of metabolic syndrome criteria was found for the duration and percentage of sedentary time and the average length of a sedentary bout (all P < 0.01). The intensity during sedentary time and the number of breaks in sedentary time had a significant negative trend with the number of metabolic syndrome criteria (all P < 0.01).
Figure 1 Adjusted mean values* and standard errors of the five sedentary variables according to the number of metabolic syndrome criteria†. *Adjusted for age and sex. †All P < 0.01. P value is based on test for trend using linear regression (more ...)
The relationship between each sedentary variable and metabolic syndrome is presented in . Model 1, adjusted for age and sex, shows the greater likelihood of having metabolic syndrome in highest quartiles of sedentary time duration, percent sedentary time, and average length of a sedentary bout. Further, compared with the highest quartile, the lowest quartile of the intensity during sedentary time and the number of sedentary breaks was associated with an increased likelihood of metabolic syndrome. Model 2 was additionally adjusted for ethnicity, alcohol consumption, smoking, and BMI, and model 3 was additionally adjusted for diabetes and heart disease. In model 3, a higher percentage of sedentary time out of total wear time (quartile 2: odds ratio [OR] 1.52 [95% CI 1.04–2.21]; quartile 3: 1.59 [1.02–2.49]; quartile 4: 1.61 [1.05–2.48]) and fewer sedentary breaks (quartile 3: 1.50 [1.02–2.21]) were related to a significantly increased likelihood of metabolic syndrome. Percentage sedentary time and sedentary breaks remained statistically significant after additional adjustment for physical activity in model 4. A higher intensity during sedentary time was related to an increased likelihood of metabolic syndrome in model 2 (quartile 4: 1.66 [1.03–2.67]) but was no longer statistically significant in models 3 and 4 (1.59 [0.96–2.62]), although the test for trend over the intensity categories remained statistically significant (P = 0.05). In additional analysis we adjusted for minutes of moderate-to-vigorous physical activity in model 4 instead of average counts per minute during active time, which did not change our results. Further, the relation between the intensity during sedentary time and sedentary breaks with metabolic syndrome did not change after adjustment for total sedentary time (data not shown).
ORs and 95% CI of metabolic syndrome according to quartiles of sedentary behavior