Table 2.

Daytime Napping in Relation to Parkinson Disease at Different Stages,^a With Further Adjustment for Nighttime Sleeping or Limited to Participants Reporting 7–8 Hours of Nighttime Sleeping, NIH-AARP Diet and Health Study

	Clinical Stage in Reference to Exposure Assessment in 1996–1997b
	Established				Recent				Prediagnostic
	PD	No PD	ORc	95% CI	PD	No PD	ORc	95% CI	PD	No PD	ORc	95% CI
Further adjustment for hours of nighttime sleeping
None (ref)	77	111,237	1.0		165	111,237	1.0		322	111,237	1.0
<1 hour	135	84,971	1.9	1.4, 2.5	164	84,971	1.1	0.9, 1.4	352	84,971	1.2	1.0, 1.3
≥1 hours	54	16,997	3.4	2.4, 4.9	65	16,997	2.3	1.7, 3.1	94	16,997	1.5	1.2, 2.0
P for trend	<0.0001				<0.0001				0.0004
Limited to participants reporting 7–8 hours of nighttime sleeping
None (ref)	39	73,409	1.0		126	73,409	1.0		214	73,409	1.0
<1 hour	72	52,918	2.1	1.4, 3.1	108	52,918	1.0	0.8, 1.3	227	52,918	1.2	1.0, 1.4
≥1 hour	13	8,485	2.4	1.3, 4.5	40	8,485	2.4	1.7, 3.5	51	8,485	1.6	1.2, 2.2
P for trend	0.0009				<0.0001				0.0019

Abbreviations: CI, confidence interval; NIH, National Institutes of Health; OR, odds ratio; PD, Parkinson disease; ref, reference.

^aEstablished cases: diagnosed before 1995; recent cases, diagnosed in 1995–1999; prediagnostic cases: diagnosed in 2000 and after.

^bPD: number of Parkinson disease cases; no PD: number of participants without Parkinson disease.

^cCovariates included age, sex, race, smoking status, daily caffeine intake, physical activity, daytime napping, and nighttime sleeping.