Table 5.

GAMM showing the association between the amount of social activity (in individuals who socialize at least once) and subsequent sleep duration

Variable	Estimate	SE	t-value	P value
Parametric coefficients
Intercept	2.89	4.27	0.68	0.498
Workday	−17.51	2.77	−6.32	<0.001
Smooth terms	EDF	RefDF	F-value
Social activity	2.326	9	1.26	0.003
Random intercept for participant	0.00	436	0.00	1.00

GAMM, generalized additive mixed-effect model; EDF, effective degrees of freedom; RefDF, reference degrees of freedom. All smooth terms are centered at zero. P values for smooth terms represent a test of whether the term is different to a flat line.