Table 2.

Multivariate Poisson Regression Models for Associations Among Chronotype, Sleep Characteristics, and WMSDs Among Nurses

Predictor variable	Model 1		Model 2		Model 3a
	PR	95% CI	PR	95% CI	PR	95% CI
Chronotype
Morning (reference)	1.00		1.00		1.00
Evening	1.48**	[1.15, 1.90]	1.37*	[1.06, 1.76]	1.32*	[1.02, 1.72]
Intermediate	1.27	[0.94, 1.71]	1.21	[0.89, 1.64]	1.17	[0.84, 1.63]
Sleep duration ≤ 6 hours			0.90	[0.71, 1.14]	0.87	[0.69, 1.10]
Sleep onset latency ≥ 30 minutes			1.32*	[1.03, 1.69]	1.37*	[1.06, 1.76]
Sleep episodes ≥ 2/day			0.97	[0.73, 1.30]	0.93	[0.68, 1.27]
Sleep-promoting substance (yes)			1.39**	[1.12, 1.75]	1.35**	[1.08, 1.68]
Sleep disturbances (moderate/severe)			1.31†	[0.96, 1.80]	1.18	[0.84, 1.65]
BMI
Normal					1.00
Overweight					1.72**	[1.28, 2.30]
Obese					1.54**	[1.12, 2.12]

Note. WMSD = work-related musculoskeletal disorder; PR = prevalence ratio; CI = confidence interval; BMI = body mass index.

^aModel 3 was also adjusted for age, gender, race, regular exercise, and shift work, which were not associated with WMSDs.

^†p < .10.

^*p < .05.

^**p < .01.