Study Participants and Baseline Characteristics
Our analysis included 5,270 male individuals, 43.2% described themselves as current alcohol drinkers and 2.7% described themselves as former alcohol drinkers. Table 1 shows the baseline characteristics of study participants stratified by alcohol drinking status. There were statistically significant differences in some of the baseline characteristics across the 3 categories of alcohol status. Former drinkers had higher baseline blood pressure levels and were more likely to be former smokers than the other two groups, and were mostly non-farmers. Compared with never drinkers, current drinkers had higher blood pressure levels and a higher proportion of them were former smokers and current smokers. The rate of cancer incidence between the three categories of alcohol status was significantly different. Former drinkers had the highest rate of cancer incidence (12.1), while never drinkers and current drinkers had lower cancer rates, at 4.8% and 5.6%, respectively. For comparison, the drinking characteristics of the female participants by drinking status are summarized in Supplemental Table S1.
Effects of Alcohol Consumption on Cancer Incidence
Compared with never drinkers (Table 2), former drinkers had a higher risk of cancer (OR 2.46, 95% CI [1.43,4.23]), after adjustment for age, systolic blood pressure, diastolic blood pressure, body mass index, fasting glucose, total cholesterol, triglycerides, high density lipoprotein cholesterol, smoking status, education and occupation. Current drinkers had a non-significant increased risk for cancer in both the crude model (OR 1.17, 95%CI [0.92, 1.49]) and the adjusted model (OR 1.12, 95%CI [0.87, 1.45]). Among current drinkers, those who drank more than 400g/week had a significantly increased risk of cancer (([OR] 1.66, 95% [CI] ( 1.18-2.34)), while the risk was reduced in the other categories of consumption amount in the adjusted model (≤200g / week: [OR] 0.87, 95% [CI] (0.59,1.28);> 200-≤400g / week : [OR] 0.99, 95% [CI] (0.68, 1.44); P for trend across the three categories of intake=0.032).In the female population (Supplemental Table S2), compared with never drinkers, the cancer risk associated with drinking still increased but was not significant, probably due to the low number of female drinkers in this Chinese rural population.
Effects of Alcohol Consumption on Cancer Incidence Among Current Drinkers
For current drinkers, the unadjusted covariate model showed that (Table 3 and figure 1), for every 100g / week increase in alcohol consumption, the risk of cancer increased by 15% ([OR] 1.15, 95% [CI] (1.07, 1.25)). With low alcohol consumption (≤200g/week) as the reference, for moderate alcohol consumption (>200-≤400g/week), the incidence of cancer showed an upward trend, while for heavy alcohol consumption (>400g/week), the cancer incidence increased significantly ([OR] 2.01, 95% [CI] (1.30, 3.11)). In the adjusted covariate model, the results obtained were similar to the unadjusted model. For every 100g / week increase in alcohol consumption, the risk of cancer increased ([OR] 1.15, 95% [CI] (1.06, 1.25)). With low alcohol consumption as the reference, moderate drinking had no significant increase in cancer risk, while heavy alcohol consumption showed a significant increase in cancer risk. (>200-≤400g/week: [OR] 1.14, 95% [CI] (0.70,1.86); >400g/week: [OR] 1.94, 95% [CI] (1.21,3.10)). The analogous analyses for females was not completed due to the low number of current female drinkers.
Stratified Analysis of Alcohol Consumption and Cancer Incidence Among Current Drinkers
Additional stratified analyses were conducted to assess any effect modification of risk factors on the relationship between alcohol drinking and cancer risk. Age was divided into three categories: <49.4 years old, ≥49.4 -<53.5 and ≥53.5 years old. After adjusting for relevant covariates, among males younger than 53.5 years old, alcohol consumption and cancer risk had no statistically significant correlation. However, among males aged 53.5 years and older , alcohol consumption was negatively correlated with cancer risk ([OR] 1.26, 95% [CI] (1.12,1.42)), and cancer incidence increased with increasing age (p for interaction= 0.032) (Table 4).
Triglycerides were divided into two categories according to the clinical cut point (150mg / dL). It was found that among current drinkers, the risk of cancer increased in participants with higher triglycerides (<150mg/dL: [OR] 1.10, 95% [CI] (1.01, 1.20); ≥150mg/dL: [OR] 1.50, 95% [CI] (1.20, 1.88), p for interaction = 0.018). High-density lipoprotein cholesterol was divided into two groups according to its clinical cut point (40 mg/dL). Among current drinkers with HDLC <40 mg/dL, cancer risk increased the most ([OR] 2.03, 95% [CI] (1.36, 3.04)), while for those with HDLC ≥40 mg/dL, the increase in cancer incidence risk was relatively low ([OR] 1.10, 95% [CI] (1.01, 1.20)), and the difference was statistically significant (P for interaction = 0.006).