. Author manuscript; available in PMC: 2014 Feb 1.

Published in final edited form as: Ann Neurol. 2013 Jan 29;73(2):236–245. doi: 10.1002/ana.23820

Table 4.

Pooled estimates of risk of amyotrophic lateral sclerosis associated by categories of vitamin C supplement intake

Vitamin C Supplement	Non Users	<400 mg/day	400–700 mg/day	≥700 mg/day	P^a_trend	P^b_{heterogeneity}
Men
Cases	284	203	96	73
Multivariate-adjusted HR (95% CI)^c	1.00 [ref]	1.08 (0.62–1.87)	1.13 (0.70–1.83)	0.98 (0.60–1.62)	0.90	0.57
Women
Cases	171	140	69	57
Multivariate-adjusted HR (95% CI)^c	1.00 [ref]	0.86 (0.64–1.17)	1.01 (0.71–1.45)	0.99 (0.67–1.46)	0.45	0.75
Pooled analysis
Multivariate-adjusted HR (95% CI)^c	1.00 [ref]	0.99 (0.72–1.37)	1.13 (0.88–1.45)	1.04 (0.81–1.35)	0.68	0.82

P_trend calculated using median value for each quintile

P- value for heterogeneity is calculated from the Q-statistic and is used to quantify differences between studies.

Adjused for age (years), sex, smoking status (never, past, current), total vitamin E intake (quartiles), body mass index (<23, 23-<25, 25-<30, ≥30), physical activity (low, average, high), educational level (<high school, high school, >high school), and total calories.