TABLE 2.

Adjusted HRs and 95% CIs of PD by category of total nicotine intake at baseline¹

Nicotine consumption	Quintile 1	Quintile 2	Quintile 3	Quintile 4	Quintile 5	P trend
Women
Median, μg	0.31	0.59	0.87	1.30	2.78
Cases, n	59	55	56	71	55
Person-years	134,902	142,362	148,948	154,916	157,694
Crude incidence rate, per 100,000 person-years	44	39	38	46	35
HR (95% CI)
Age adjusted	1 (Ref.)	0.86 (0.60, 1.25)	0.83 (0.57, 1.20)	1.00 (0.70, 1.41)	0.78 (0.54, 1.14)	0.35
Age and total energy adjusted	1 (Ref.)	0.79 (0.54, 1.15)	0.73 (0.50, 1.07)	0.87 (0.60, 1.25)	0.68 (0.46, 1.00)	0.15
Multivariate2	1 (Ref.)	0.79 (0.54, 1.15)	0.72 (0.48, 1.06)	0.87 (0.59, 1.26)	0.64 (0.42, 0.96)	0.09
Further adjusted for environmental tobacco smoke exposure status,3 family history of PD,4 and other NSAID use (e.g., ibuprofen)5	1 (Ref.)	0.79 (0.54, 1.15)	0.72 (0.48, 1.06)	0.86 (0.59, 1.26)	0.64 (0.42, 0.97)	0.10
Men
Median, μg	0.27	0.52	0.76	1.12	2.00
Cases, n	57	63	62	70	53
Person-years	78,818	87,043	87,084	84,313	82,740
Crude incidence rate, per 100,000 person-years	72	72	71	83	64
HR (95% CI)
Age adjusted	1 (Ref.)	0.99 (0.68, 1.42)	0.92 (0.63, 1.33)	1.00 (0.70, 1.43)	0.76 (0.52, 1.12)	0.16
Age and total energy adjusted	1 (Ref.)	0.97 (0.66, 1.40)	0.88 (0.60, 1.29)	0.95 (0.65, 1.38)	0.71 (0.48, 1.07)	0.09
Multivariate2	1 (Ref.)	0.97 (0.66, 1.42)	0.87 (0.59, 1.29)	0.96 (0.65, 1.44)	0.77 (0.50, 1.20)	0.26
Further adjusted for environmental tobacco smoke exposure status,3family history of PD,4 and other NSAID use (e.g., ibuprofen)5	1 (Ref.)	0.96 (0.65, 1.40)	0.88 (0.59, 1.31)	0.98 (0.65, 1.46)	0.81 (0.52, 1.26)	0.37
Pooled analysis6
Multivariate2	1 (Ref.)	0.87 (0.67, 1.14)	0.79 (0.60, 1.04)	0.91 (0.69, 1.20)	0.70 (0.51, 0.94)	0.04
Further adjusted for environmental tobacco smoke exposure status,3 family history of PD,4 and other NSAID use (e.g., ibuprofen)5		0.87 (0.66, 1.14)	0.79 (0.60, 1.04)	0.91 (0.69, 1.20)	0.71 (0.52, 0.96)	0.06

¹NSAID, nonsteroidal anti-inflammatory drug; PD, Parkinson disease.

²Adjusted for age, BMI, physical activity, caffeine, alcohol, total carotenoid intake, total energy intake, overall dietary patterns, postmenopausal status, and current postmenopausal hormone use (premenopausal/postmenopausal without hormone use/postmenopausal with hormone use, women only).

³Environmental tobacco smoke exposure status was collected in 1982 for women and 2004 for men.

⁴Family history of PD (father, mother, and siblings) was collected in 2008.

⁵Other NSAID use (e.g., ibuprofen) was collected in 1990 for women and 1986 for men.

⁶Fixed-effects model was used, P-heterogeneity = 0.98.