. Author manuscript; available in PMC: 2011 Nov 2.

Published in final edited form as: Am J Epidemiol. 2007 Nov 15;167(3):321–329. doi: 10.1093/aje/kwm302

Table 2.

Cross-sectional relationships^* of duration of sleep (hours) with BMI and waist circumference at phase 5 (1997–1999). The Whitehall II Study, London, England (n=5,021).

	≤5h (n=380)	6h (n=1,650)	7h (n=2,153)	8h (n=774)	≥9h (n=64)	p-value^†
	Coef. (95% CI)	Coef. (95% CI)	reference	Coef. (95% CI)	Coef. (95% CI)	Linear	Non-linear
BMI (Kg/m²)
Model 1	1.09^‡ (0.66, 1.52)	0.41^‡ (0.16, 0.66)	0	−0.28 (−0.6, 0.04)	−0.22 (−1.19, 0.75)	<0.001	0.92
Model 2	0.94^‡ (0.51, 1.36)	0.44^‡ (0.19, 0.68)	0	−0.27 (−0.59, 0.04)	−0.45 (−1.41, 0.52)	<0.001	0.55
Model 3	0.82^‡ (0.38, 1.26)	0.43^‡ (0.18, 0.68)	0	−0.25 (−0.57, 0.07)	−0.62 (−1.59, 0.35)	<0.001	0.84
Waist (Cm)
Model 1	2.90^‡ (1.69, 4.11)	0.97^‡ (0.26, 1.68)	0	−1.17^‡ (−2.1, −0.24)	0.25 (−2.48, 2.98)	<0.001	0.23
Model 2	2.43^‡ (1.23, 3.62)	1.04^‡ (0.35, 1.74)	0	−1.18^‡ (−2.09, −0.27)	−0.73 (−3.43, 1.97)	<0.001	0.68
Model 3	1.88^‡ (0.64, 3.12)	0.93^‡ (0.23, 1.64)	0	−1.09^‡ (−2.01, −0.18)	−1.38 (−4.06, 1.3)	<0.001	0.95

Results are expressed as β coefficients and 95% confidence intervals (CI) compared to 7h of sleep category

^†

P-values for test of linear and nonlinear trends

^‡

Significant p-values (p ≤ 0.05) for contrast of that specific category versus reference category

Model 1: adjusted for age, sex, employment

Model 2: Model 1 + alcohol consumption, smoking, physical activity and cardio-vascular drugs

Model 3: Model 2 + mental and physical scores (SF36), depressive symptoms and use of hypnotics