Table 5.

Pooled multivariable relative risks of pancreatic cancer for folate intake by smoking status^*

Folate intake by smoking strata	No. of cancers	RR (95% CI)				Ptrend‡	Pbetween-studies heterogeneity§	Pinteraction║
		Quartile of folate intake†
		1	2	3	4
Dietary folate
Never¶	766	1.00 (referent)	0.92 (0.75 to 1.14)	0.92 (0.75 to 1.13)	0.94 (0.76 to 1.16)	.56	.82
Ever	1385	1.00 (referent)	0.96 (0.79 to 1.15)	0.99 (0.84 to 1.15)	1.05 (0.88 to 1.24)	.42	.26	.35
Total folate#
Never¶	631	1.00 (referent)	0.90 (0.72 to 1.12)	0.87 (0.70 to 1.09)	0.77 (0.61 to 0.97)	.08	.86
Ever	903	1.00 (referent)	0.90 (0.70 to 1.14)	1.06 (0.79 to 1.43)	1.09 (0.89 to 1.32)	.31	.37	.04

^*Folate intake was adjusted for energy intake. CI = confidence interval; RR = relative risk.

^†Adjusted for body mass index (kg/m², continuous), diabetes (yes, no), alcohol intake (g/d; 0, 0.1–14.9, 15.0–29.9, ≥30), energy intake (kcal/d, continuous), and cigarette smoking (never, former [<15, ≥15 pack-years], current [<40, ≥40 pack-years]). Age in years and year of questionnaire return were included as stratification variables.

^‡P values were calculated using two-sided Wald test.

^§P values were for the highest quartile and were calculated using the Q statistic.

^‖P values for the highest quartile for the tests for interaction between smoking status and folate intake were calculated using the two-sided Wald test.

^¶The Alpha-Tocopherol Beta-Carotene Cancer Prevention Study was excluded from this stratum because the cohort included only current smokers.

^#The Melbourne Collaborative Cohort Study and the Canadian National Breast Screening Study were not included because total folate intake data were not available in these two studies. The Alpha-Tocopherol Beta-Carotene Cancer Prevention Study and the Netherlands Cohort Study were also excluded because total folate intake in these two studies was primarily or only from diet.