TABLE 4.

HRs and 95% CIs for the association between plasma vitamin C concentrations and risk of upper gastrointestinal cancers in the Linxian General Population Nutrition Intervention Trial cohort overall and by season¹

	All				Winter, 1999				Spring, 2000
Cancer type Vitamin C concentration	No. of cases	HR2	95% CI	P value	No. of cases	HR3	95% CI	P value	No. of cases	HR3	95% CI	P value	P-interaction
ESCC
≤28 umol/L	275	1.00	Ref		46	1.00	Ref		120	1.00	Ref
>28 umol/L	343	0.89	0.69, 1.14	0.37	268	0.90	0.61, 1.33	0.50	75	0.84	0.60, 1.18	0.33	0.89
Gastric adenocarcinoma
≤28 umol/L	234	1.00	Ref		43	1.00	Ref		86	1.00	Ref
>28 umol/L	233	0.73	0.56, 0.97	0.030	171	0.66	0.44, 1.00	0.050	50	0.77	0.53, 1.13	0.19	0.43
Cardia adenocarcinoma
≤28 umol/L	159	1.00	Ref		34	1.00	Ref		57	1.00	Ref
>28 umol/L	170	0.73	0.52, 1.00	0.050	133	0.64	0.41, 1.00	0.053	37	0.82	0.53, 1.27	0.38	0.16
Noncardia adenocarcinoma
≤28 umol/L	63	1.00	Ref		10	1.00	Ref		34	1.00	Ref
>28 umol/L	75	0.74	0.48, 1.14	0.18	46	0.75	0.37, 1.51	0.42	17	0.70	0.38, 1.26	0.23	0.46

¹Plasma vitamin C concentrations: low, ≤28 μmol/L; normal, >28 μmol/L. ESCC, esophageal squamous cell carcinoma; Ref, reference.

²HRs were derived from Cox proportional hazard models and adjusted for 6 sex and age group categories, BMI, smoking, and Helicobacter pylori.

³HRs were derived from Cox proportional hazard models and conditioned on season of blood draw (winter/spring) and adjusted for 6 sex and age group categories, BMI, smoking, and H. pylori seropositivity.