Journal Club Alcohol and Health: Current Evidence January-February 2005

Featured Article Alcohol and Risk of Atrial Fibrillation or Flutter: A Cohort Study Frost L, Vestergaard P. Arch Intern Med. 2004;164(18):

Study Objective To examine the association between alcohol consumption and the risk of atrial fibrillation (AF) or flutter

Study Design Researchers prospectively studied 47,949 Danish participants (mean age, 56 years) over a mean follow-up of 6 years.

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

Are the Results Valid? Was the sample representative? Were the subjects sufficiently homogeneous with respect to prognostic risk? Was follow-up sufficiently complete? Were objective and unbiased outcome criteria used?

Was the sample representative? The sample was somewhat representative of people in Denmark since it was drawn from Danish population-based registries. Representativeness is limited due to the following: –Exclusion of those with endocrine or cardiovascular disease –Participation by fewer than two-thirds of those invited

Were the subjects sufficiently homogeneous with respect to prognostic risk? Researchers excluded participants with cardiovascular disease (including AF or flutter), making the sample an inception cohort. Men consuming amounts in the highest quintile drank approximately 6 standard drinks per day; women in the highest quintile drank about 3 drinks per day.

Was follow-up sufficiently complete? Follow-up was 6 years on average but varied from <1 to 8 years. The authors seem to suggest that follow- up (involving survival methods that censored subjects at the time of AF or flutter, death, emigration, or the end of the study) was 100%, assuming that all events would be captured for all people in the national registries used.

Were objective and unbiased outcome criteria used? Yes; cases were identified by diagnostic codes and confirmed by electrocardiographic tracings. But since these data were collected in the course of clinical care, diagnosis could possibly be biased (e.g., greater or lesser likelihood of recording AF or flutter based on a patient’s alcohol use).

What are the Results? How likely are the outcomes over time? How precise are the estimates of likelihood?

How likely are the outcomes over time? MenWomen # (%) with incident diagnosis of AF or flutter 374 (1.7%)182 (0.7%) Incident rates of AF or flutter (per 10,000 person-years at risk) Hazard ratios of AF or flutter (in analyses adjusted for potential confounders) Increased from 1.04 to 1.45 from the 2nd to the 5th quintile of consumption No consistent association

How precise are the estimates of likelihood? Although the confidence intervals for the hazard ratios in men did not all exclude 1, the p value for trend was The association between intake and AF or flutter in women was not statistically significant.

How Can I Apply the Results to Patient Care? Were the study patients and their management similar to those in my practice? Was the follow-up sufficiently long? Can I use the results in the management of patients in my practice?

Were the study patients similar to those in my practice? Given that the study involved a population-based cohort, subjects were not necessarily patients. Whether (and how) these Danish subjects/patients might differ from those in the United States is not clear.

Was the follow-up sufficiently long? Follow-up may not have been long enough: –Outcomes were not common. –AF or flutter is more prevalent in the elderly (the mean age of subjects at enrollment was 56 years).

Can I use the results in the management of patients in my practice? Drinking even moderate amounts of alcohol may increase the risk of AF or flutter, at least for men. This study did not have a large sample of heavy drinkers and therefore could not focus on the well-described “holiday heart.”

Can I use the results in the management of patients in my practice (cont.)? It is not clear whether results would apply to people in the United States where drinking patterns may differ than those in Denmark. AF or flutter is only one of the risks to consider when counseling patients about their drinking.