Table 3. Multivariate linear regressions of sleep parameters and positive relations with others on plasma IL-6 levels in aging women (n = 78).

Predictors	Model 1 (β)	Model 2 (β)	Model 3 (β)	Model 4 (β)
Positive relations with others, cubed	–0.31*		–1.21*	–0.31*
Sleep efficiency, cubed		–0.40†	–0.98*	–0.38†
Positive relations × sleep efficiency interaction			1.13‡
Change in R2	0.09*	0.13†	0.34†	0.22†

Standardized regression coefficients are shown. All models included the control variables listed below, and the change in R² is net of the control variables. Models 1 and 2 show the individual contributions of positive relations and sleep efficiency to plasma IL-6 levels. Model 3 shows the interaction of sleep efficiency and positive relations in predicting IL-6. Model 4 tested the extent to which sleep efficiency and positive relations independently predicted IL-6 levels. Models controlled for age, marital status, years of education, pretax family income, chronic health conditions, medication use, alcohol consumption, and smoking. ^*, P < 0.01; †, P < 0.001; ‡, P < 0.05.