Journal Club Alcohol, Other Drugs, and Health: Current Evidence July–August 2009

Featured Article Alcohol Use and Risk of Pancreatic Cancer: The NIH-AARP Diet and Health Study Jiao L, et al. Am J Epidemiol. 2009;169(9):1043–1051.

Study Objective To determine the relationship between alcohol use and risk of pancreatic cancer.

Study Design Prospective cohort of 470,681 participants from the US National Institutes of Health (NIH)-AARP Diet and Health Study who were aged 50–71 years between 1995–1996.

Assessing Validity of an Article About Harm Are the results valid? What are the results? How can I apply the results to patient care?

Are the Results Valid? Did the investigators demonstrate similarity in all known determinants of outcomes? Did they adjust for differences in the analysis? Were exposed patients equally likely to be identified in the two groups? Were the outcomes measured in the same way in the groups being compared? Was follow-up sufficiently complete?

Did the investigators demonstrate similarity in all known determinants of outcomes? Did they adjust for differences in the analysis? Yes. –The analysis used multivariable Cox proportional hazards regression models to adjust for major potential confounders. The final models were adjusted for gender; smoking history; daily energy (k/cal), saturated fat, red meat, and folate intake; body mass index; physical activity; and self-reported history of diabetes.

Were exposed patients equally likely to be identified in the groups?  Yes. –All participants were prospectively queried about alcohol use for the 12 months prior to baseline; therefore, there should be no differential ascertainment of alcohol exposure. –The exposure was presumed to be static, and those who reported no alcohol consumption may have included former drinkers.

Were the outcomes measured in the same way in the groups being compared?  Subjects were contacted on a regular basis as part of the observational study, but there were no procedures for active surveillance of pancreatic cancer.  Incident pancreatic cancer outcomes were determined through state cancer registries. Fatal cases were determined through linkage with the National Death Index.

Was follow-up sufficiently complete? Approximately 4% of participants were lost to follow-up.

What are the Results? How strong is the association between exposure and outcomes? How precise is the estimate of the risk?

How strong is the association between exposure and outcome? How precise is the estimate of the risk? Beverage-specific effects revealed no increase in risk for consumers of any amounts of beer or wine or for consumers of liquor up to 3 drinks per day. Compared with light drinkers, the RR of developing pancreatic cancer was –1.45 (95% confidence interval (CI): 1.17, 1.80) in subjects who drank ≥3 drinks of beer or wine per day; –1.62 (95% CI: 1.24, 2.10) in subjects who drank ≥3 drinks of liquor per day; and –1.41 (95% CI: 1.01, 2.00) in subjects who had quit smoking 10 or more years earlier.

How Can I Apply the Results to Patient Care? Were the study patients similar to the patients in my practice? Was the duration of follow-up adequate? What was the magnitude of the risk? Should I attempt to stop the exposure?

Were the study patients similar to the patients in my practice? The sample included 470,681 men and women aged 50–71 years from 6 US states (California, Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania and 2 US metropolitan areas (Atlanta and Detroit). Patients with cancer or extreme dietary intake (>2 interquartile ranges above the 75th or below the 25th percentile of Box-Cox log- transformed energy intake) were excluded.

Was the duration of follow-up adequate? Average follow-up time was 7.3 years, which may not be long enough to establish a strict causal relationship unless one assumes that baseline drinking approximates adult lifetime alcohol exposure.

What was the magnitude of the risk? Consuming >3 drinks of alcohol or liquor per day was associated with an approximately 50% increase in risk for pancreatic cancer.

Should I attempt to stop the exposure? The potential additive risk should be discussed with individuals in light of other known risk factors for pancreatic cancer including tobacco use, diet, and high caloric intake.