Relationship between Sitting Time and Insulin Resistance in 6931 U.S. Adults: The Mediating Role of Abdominal Adiposity

Table 2

Mean differences in L-HOMA-IR across the three categories of sitting time in U.S. men and women, after adjusting for the covariates.

Criterion variable: L-HOMA-IR	Model
Covariates
Demographics	1				12.6	<0.0001
Demographics + smoking	2				12.0	<0.0001
Demographics + activity	3				10.5	<0.0001
Demographics + BMI	4				3.7	0.0293
Demographics + WC	5				1.1	0.3349
All covariates	6				1.0	0.3881

L-HOMA-IR: natural log of HOMA-IR (homeostatic model assessment for insulin resistance); SE: standard error of the L-HOMA-IR mean; WC: waist circumference. The demographic covariates were age, sex, race, and year of assessment. Means with the same superscript letter (i.e., a, b, and c) on the same row did not differ significantly from each other. Model 1 adjusted for differences in the demographic variables only. Model 2 controlled for the model 1 covariates plus cigarette smoking. Model 3 controlled for the model 1 covariates plus physical activity. Model 4 adjusted for the model 1 covariates plus BMI. Model 5 adjusted for the model 1 covariates plus waist circumference. Model 6 adjusted for all the covariates simultaneously. Sitting time was divided into tertiles. However, because the tertile cut points included many participants, differed across the 3 sitting time categories (low: , moderate: , and high: ). These frequencies are listed as weighted values due to the person-level weighted adjustments used by NHANES.