Table 2.

Hazard Ratios for Traumatic Brain Injury for Prodromal Parkinson Disease Cases Compared to Controls

	Basic Modela,b			Fully Adjusted Model a,c,g
	HR	95% CI	p-value	HR	95% CI	p-value
Years prior to PD diagnosis
0 to < 1 year prior	4.22*	4.02 – 4.43	< 0.0001	3.93*	3.74 – 4.13	< 0.0001
1 to < 2 years prior	2.47*	2.33 – 2.62	< 0.0001	2.30*	2.17 – 2.44	< 0.0001
2 to < 3 years prior	2.17	2.03 – 2.31	< 0.0001	2.01	1.89 – 2.15	< 0.0001
3 to < 4 years prior	2.12*	1.98 – 2.28	< 0.0001	1.98*	1.85 – 2.12	< 0.0001
4 to < 5 years prior	1.76	1.63 – 1.89	< 0.0001	1.64	1.52 – 1.77	< 0.0001
Age, per Year	1.056	1.054 – 1.058	< 0.0001	1.056	1.054 – 1.058	< 0.0001
Female	1.35	1.31 – 1.38	< 0.0001	1.53	1.48 – 1.57	< 0.0001
Race/Ethnicity
White	1.00	(Reference)		1.00	(Reference)
Black	0.89	0.84 – 0.94	< 0.0001	0.86	0.81 – 0.91	< 0.0001
Pacific Islander/Other	0.81	0.70 – 0.93	0.003	0.87	0.75 – 0.99	0.04
Asian	0.85	0.77 – 0.94	0.001	0.88	0.79 – 0.97	0.01
Hispanic	0.92	0.84 – 1.01	0.089	0.93	0.84 – 1.02	0.10
Native American	1.15	0.94 – 1.41	0.177	1.07	0.87 – 1.31	0.53
Unknown	1.18	0.80 – 1.75	0.410	1.16	0.78 – 1.72	0.46
Modified CCId
0				1.00	(Reference)
1				1.28	1.23 – 1.32	< 0.0001
2				1.45	1.40 – 1.51	< 0.0001
3 or more				1.77	1.71 – 1.83	< 0.0001
Smokinge,f				1.60	1.53 – 1.67	< 0.0001
Alcohol (heavy use)f				1.89	1.71 – 2.09	< 0.0001

^aBased on 88,973 PD cases and 117,598 controls from a case-control study; excludes 817 cases and 497 controls with prior head injury. Abbreviations: HR = hazard ratio, CI = 95% confidence intervals.

^bAdjusted for age, sex, and race/ethnicity.

^cAdjusted for age, sex, race/ethnicity, modified CCI as of baseline, smoking, and alcohol use.

^dModified CCI (truncated Charlson comorbidity index as described by Deyo²⁴ and Quan²⁵ methods) at year of study entry for each participant.

^ePredicted probability of ever vs. never smoking.

^fSee Table 1 footnotes for diagnosis and procedure codes used to identify ever smoking, and heavy alcohol use.

^gThe difference in log hazard ratios between the year prior to diagnosis and the average of all previous years was 0.6958 (CI 0.6350, 0.7565, p-value < .0001). Additionally, we compared the difference in log hazard ratios between consecutive years as follows: 1 year prior vs. 2 years prior (0.5426, CI 0.4644, 0.6208, p-value < .0001), 2 years prior vs. 3 years prior (0.1358, CI 0.0472, 0.2244, p-value 0.0027), 3 years prior vs. 4 years prior (0.0156, CI -0.0803, 0.1115, p-value 0.7496), and 4 years prior vs. 5 years prior (0.1741, CI 0.0712, 0.2770, p-value 0.0009). All were significant except for 3 years prior vs. 4 years prior.

^*We indicated with an asterisk(*) if there was a statistically significant increase from the previous year.