We used Cox proportional hazards modeling to estimate the relative risk (RR) of incident gout in all multivariate analyses (SAS Institute Inc, Cary, North Carolina). We categorized total daily vitamin C intake into 5 categories: less than 250, 250 to 499, 500 to 999, 1000 to 1499, and 1500 mg or more.20,21 In addition, we categorized daily supplemental vitamin C intake into 6 categories: none, 1 to 249, 250 to 499, 500 to 999, 1000 to 1499, and 1500 mg or more and daily dietary vitamin C intake into 6 categories: less than 50, 50 to 99, 100 to 199, 200 to 299, and 300 mg or more. Multivariate models were adjusted for age (continuous), total energy intake (continuous), alcohol use (7 categories), BMI (5 categories), use of diuretics (thiazide or furosemide; yes or no), history of hypertension (yes or no), history of chronic renal failure (yes or no), and daily average intake of total meats (quintiles), seafood (quintiles), dairy foods (quintiles), fructose (quintiles), and coffee (regular and decaffeinated in 4 and 3 categories, respectively).3- 5 Trends in gout risk across categories of vitamin C intake were assessed in Cox proportional hazards models by using the median values of intake for each category to minimize the effect of outliers. The RRs for the continuous measures for vitamin C intake indicate the increase in risk associated with an average increment of 500 mg/d. We conducted analyses stratified by BMI (<25 vs ≥25), alcohol use (median: ≤5.5 vs >5.5 g/d), and daily dairy intake (median: ≤1.6 vs >1.6 servings) to assess possible effect modification. We tested the significance of the interaction using a likelihood ratio test by comparing a model with the main effects of vitamin C intake and the stratifying variable and the interaction terms with a reduced model with only the main effects. For all RRs, we calculated 95% confidence intervals (CIs). All P values are 2-sided.