Patterns of alcohol consumption and acute myocardial infarction: a case-crossover analysis.
Summary (3 min read)
- Regular moderate alcohol consumption without heavy drinking has been shown to be a protective factor for cardiovascular disease including acute myocardial infarction (AMI) in particular [1, 2] .
- Other protective factors include regular physical activity and daily consumption of fruits and vegetables, whereas hyperlipidemia, smoking, hypertension, diabetes mellitus and obesity have been identified as major modifiable risk factors for AMI [3, 4] .
- Moreover, the results of these controlled studies have been mixed.
- As reviewed by McKee and Britton  and further sources [1, 2] , a number of possible mechanisms have been discussed in the literature explaining the acute effects of binge drinking on CHD events.
- These events might include arrhythmia, ischaemia, and possibly thrombotic processes'.
Study Population and Data Collection
- Patients were recruited in three major hospitals in the German-speaking part of Switzerland -a university hospital, a county hospital and a city hospital.
- Through collaboration with the staff it was also possible to track all 673 patients who were hospitalized for first time AMI (ICD I21; for detailed definition see below) in the study hospitals between July 26, 2005 and November 15, 2006.
- The major reason why not all 673 patients were eligible for interviews was the early relocation of 239 patients (35.5%) within 24 h to another hospital, mainly because of regional responsibility and bed availability.
- The interviews were conducted in half of the study population within 38 h after the AMI.
- The patients who refused to participate in the interview did not differ in gender distribution with the patients who participated in the interviews, but they were on average 8 years older.
- The case-crossover methodology used in the present study was introduced by Maclure  in the early 1990s to study transient effects on the risk of rare acute events.
- An important feature of the case-crossover design is that the control information for each patient is based on his or her own past exposure experience.
- The patient was first asked to report time of infarction.
- Alcohol consumption in this hazard period was compared with the corresponding time period 1 week prior.
- Participants were asked in detail about their drinking behavior: frequency, including binge drinking, type (e.g. wine, beer, spirits), and amount on a usual drinking occasion in deciliters (dl).
- Patients who did not drink at least once a month during the 3 months prior, but drank once a month during some period of their life, were defined as former drinkers.
- These categories were used in a landmark study by Jackson et al. [21, 35] , who first examined the short-term influence of alcohol intake on the risk of CHD events via the casecrossover design.
- The categories regarding the frequency of binge drinking in the prior year were as follows: never, less than once a month, every month, every week, every day  .
Basic Medical Data
- Basic medical data were obtained from the medical records of the patients with informed consent.
- Information was obtained on the presence of arterial hypertension (documented pressure 1 140/90), hyperlipidemia, diabetes mellitus and prior angina pectoris as well as regular medication before the event.
- Further data such as smoking history, weight, height, family history of MI, etc. was asked about in their questionnaire.
- The authors study was approved by the responsible cantonal research ethics boards of the participating hospitals.
- Conditional logistic regression was used to estimate the odds ratios for alcohol consumption in general and binge drinking, within the time before the AMI compared to the same time span 1 week prior  .
- Conditional regression tries to answer the question of a causal impact of drinking before the event.
- The sample size was determined a priori, in order to detect a difference in proportions of 10% when the proportion of discordant pairs was expected to be 30% and the method analysis was a McNemar's test of equality of paired proportions with a 0.05 two-sided significance level.
- Furthermore, the authors compared the usual drinking patterns of their sample with the Swiss Health Survey conducted in the year 2002  .
- This sample comprised of 19,706 individuals older than 15 years and living in Switzerland (Swiss or foreign nationality), who were interviewed by phone and 16,141 of whom also completed a written questionnaire.
Description of the Sample
- None of the patients had a cardiac rupture, 52% of the patients were hypertensive and 35.6% had the diagnosis of hyperlipidemia.
- 4% of the sample reported daily drinking, with 3 patients (1.2% of the study group) drinking more than once a day.
- Table 3 also provides information about the beverage choice in men and women, mainly wine and beer for men, and wine for women.
Drinking Patterns in the Hazard and Control Period
- Drinking moderately in the 12-hour hazard period increased the risk of AMI marginally significant compared with no alcohol consumption (OR 2.3; 95% CI 0.97-5.2).
- 18 persons were exposed in terms of moderate drinking in the hazard period and 8 persons were exposed in the control period.
- The authors did not find any significant differences regarding binge drinking before AMI, using the international definition of 4 or more for women and 5 or more glasses of alcohol for men (see Method section).
Comparison of Drinking Patterns with the General Population
- Patterns of alcohol consumption varied significantly between AMI patients and the general population (likelihood ratio 2 : 40.0; d.f. = 3; p ! 0.001).
- The standardized residuals were significant for the categories of abstention and irregular drinking.
- In addition, binge drinking occasions were significantly more frequent among AMI patients: both 'less than monthly' (20.7 vs. 10.9%) and 'monthly or more frequent' binge drinking occasions were about twice as prevalent in their study population (6.8 vs. 3.4%).
- Both rates had significant standardized residuals of 4.4 and 2.7, respectively.
- The authors found that drinking alcohol 12 h before the AMI increased the risk for such an event.
- Obviously, their study is not without limitations.
- As patients from suburban or rural hospitals are often referred to these hospitals for further examinations and therapy, almost half of their study population was based outside the city.
- While the chosen design controls for a potential effect of day of the week, the possibility that recall bias is larger for the events of 1 week prior compared to more recent time periods, cannot be excluded.
- Given the facts that drinking prior to the event resulted in an increased risk for AMI and that a comparison with the general population of a similar sex and age distribution showed higher rates of previous year heavy drinking occasions in their sample, the hypothesis that heavy drinking occasions lead to an increase in risk for AMI received some support.
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Q1. What are the contributions mentioned in the paper "Patterns of alcohol consumption and acute myocardial infarction: a case-crossover analysis" ?
This study tested the hypothesis that heavy drinking ( binge drinking ) increases the risk of subsequent acute myocardial infarctions ( AMI ), whereas light to moderate drinking occasions decrease the risk. In a recent study of alcohol drinking patterns and myocardial infarction ( MI ) in women, those who drank at least once a month in a way that ‘ their speech was slurred or they became unsteady on their feet ’, a behavior classified as ‘ intoxication ’, had nearly a threefold risk of MI when compared to lifetime abstainers. Based on these epidemiological findings, this study tested the hypothesis that heavy drinking occasions ( binge drinking ) increase the risk of subsequent AMI, whereas light to moderate drinking occasions decrease the risk. Through collaboration with the staff it was also possible to track all 673 patients who were hospitalized for first time AMI ( ICD I21 ; for detailed definition see below ) in the study hospitals between July 26, 2005 and November 15, 2006. The authors used the following definition of AMI which is compatible with the national register for Acute Myocardial Infarction in Switzerland ( AMIS-plus database ): symptoms and/or ECG changes compatible with acute coronary syndrome and with the enzymes creatine kinase or creatine kinase-muscle brain at least twice the upper limits of normal. As a result, the study group consisted of 250 patients. The authors arranged with the hospitals that patients were not to be interviewed on their first day in hospital, in order to not disturb medical examinations, and in consideration of the patients with recent major complications. The other exclusion criteria were: no domicile in Switzerland ( tourists ) ( 5 persons, 0. 7 % ) ; insufficient skills in German language ( 29, 4. 3 % ) ; mental or physical inability to participate in an interview ( e. g. cerebral damages, dementia, aphasia, hypoxia, patient too confused ) ( 55 persons, 8. 2 % ) or death after admission ( 12, 1. 8 % ), involvement in another interview study ( 17 persons, 2. 5 % ) or other ( e. g. the patient left the hospital without official discharge ) ( 4 persons, 0. 6 % ). The interviews were conducted in half of the study population within 38 h after the AMI. 55 % of the patients were referred directly to the study hospital and 45 % were transferred from another hospital to the study hospital. The case-crossover methodology used in the present study was introduced by Maclure [ 33 ] in the early 1990s to study transient effects on the risk of rare acute events. Com/ear Gerlich/Krämer/Gmel/Maggiorini/ Lüscher/Rickli/Kleger/Rehm Eur Addict Res 2009 ; 15:143–149 144 discussed heavy acute alcohol intake as a potential trigger for AMI [ 16–19 ], but only a few studies in the literature have systematically investigated the effect of alcohol exposure shortly before CHD events using a case-crossover or case-control design [ 20–22 ]. As reviewed by McKee and Britton [ 24 ] and further sources [ 1, 2 ], a number of possible mechanisms have been discussed in the literature explaining the acute effects of binge drinking on CHD events. Kauhanen et al. [ 25 ] suggested that ‘ heavy acute intake of beer may involve acute triggers of severe pathophysiological events in the myocardium or the coronary arteries, or both.