Greater Hepatic Vulnerability after Alcohol Intake: METHODS Study

7 Jan
2010

Population

The present study focuses on data obtained from a sample of residents of Erie and Niagara counties in New York State, enrolled as part of a series of studies conducted between September 1995 and May 2001. A detailed report of the study design, participant enrollment, and methodology has been described previously. Potential participants were randomly identified from lists of those holding a New York State driving license from the Department of Motor Vehicles of New York for people aged 35-64 and Health Care Financing Administration rolls for people aged 65-80. Of the 6,837 potential participants identified, contacted, and found to be eligible for our study, a total of 4,065 (participation rate=59.5%) agreed to participate and were invited to the Center for Preventive Medicine at the University at Buffalo for an interview and physical examination. The exclusion criteria applied to the present analyses were race different from Caucasian or African-American (n=53); a self-reported history of chronic or acute hepatitis, cirrhosis or noncirrhotic liver disease (n=171); missing information on education, BMI, smoking status, life pack years of smoking (n=169) or on drinking habits (n=32); outliers for enzyme levels (n=3, for GGT >800; n=l, for ALT=324) or missing blood determination of liver enzymes (n=332). The remaining 3,304 participants (3,063 Caucasians and 241 African Americans, 92.7% vs. 7.3%) are included in this analysis. Excluded participants for whom information was available were different from included participants with respect to the distribution of gender (women: 45.9% vs. 53.1%, p<0.05) and race (African-American: 11.4% vs. 7.3%, p<0.05); they were also significantly older, less educated, and characterized by higher body mass index (BMI) compared to included participants (age: 61.7 vs. 58.6, p<0.01; education: 13.2 vs. 13.5, p<0.05; BMI: 28.7 vs. 28.2, p<0.05). For smoking status and total pack-years of smoking, we did not find significant differences between the two groups of participants. With regard to drinking status, the excluded participants were significantly more likely to be lifetime abstainers (13.0 vs. 9.3, p<0.01) and less likely to be current drinkers than included participants (57.9 vs. 65.8, p<0.01). For total and beverage-specific alcohol intake in the past 30 days, the two groups did not significantly differ, except for wine consumption that was significantly higher among included individuals. Finally, excluded individuals had higher average levels of all three hepatic enzymes (p<0.05) compared with included participants.

Examination

As part of the examination, participants were characterized in detail with regard to their health conditions and lifestyle habits. The health examination included measurements of anthropometric variables. Weight was measured with participants being dressed in light clothes and no shoes, using a beam balance scale (Detecto, Inc., Webb City, MO); height was measured without shoes by tape measure (Perspective Enterprises, Kalamazoo, MI), according to a standardized protocol. BMI (kg/m2) was calculated as weight (kg) divided by height in meters squared.
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Blood Determinations

A fasting blood sample was obtained for determination of routine chemistry between 7:30 and 9:30 a.m. after a fasting of eight-to-12 hours. Immediately following phlebotomy, tubes were wrapped in aluminum foil to protect them from light and kept at room temperature for 30 minutes and allowed to clot. Blood tubes were centrifuged at 3,000 Xg for 10 minutes, and 1.5 mL of serum was transferred to polypropylene screw cap vials and placed in a cooler with a cold pack. Samples were delivered by courier to Millard Fillmore Center for Laboratory Medicine (Amherst, NY) for analysis the same day. Hepatic enzymes alanine amino transferase (ALT), aspartate amino transferase (AST) and serum gamma-glutamyl transferase (SGGT) were measured by kinetic enzyme assays as part of a chemistry profile on a Paramax Automated Chemistry System.

Alcohol Intake

The interview was specifically designed to assess the past and current use of total and beverage-specific alcohol consumption. Information about alcohol intake was obtained with a computer assisted in-per-son interview. Interviewers underwent extensive training and standardization. In addition to their current consumption (past 30 days), participants were asked about their lifetime alcohol intake with the use of the Cognitive Lifetime Drinking History (CLDH). The interview included questions about the size of the container (glass, bottle) used and the amount of alcoholic beverage usually consumed in that particular container. Participants were shown models and photos of different containers with lines indicating the potential level of beverage within each container, in order to improve the accuracy of their estimates. Using a typical 28-day period as a framework, quantity-frequency questions on alcohol drinking were asked for Fridays, Saturdays, Sundays, and weekdays. Responses to the above questions were used to compute the following variables for the present analyses: a) lifetime abstainers—participants who reported consumption of less than 12 drinks during their lifetime or in any one-year period; b) noncurrent drinkers (former drinkers)—participants who reported 12 or more drinks during their lifetime or in any one-year period, but did not consume an alcoholic beverage at least once in the past 30 days; c) current drinkers—participants who consumed at least one alcoholic beverage in the past 30 days (daily and nondaily consumption); d) ounces of ethanol consumed in the past 30 days (both total and beverage-specific); e) usual ounces of ethanol consumed per drinking day in the past 30 days (measure of intensity of consumption).

Statistical Analysis

Statistical analysis was performed using the Statistical Package for Social Sciences (SPSS-11.0, SPSS Inc., Chicago, IL). We evaluated the distributions of the continuous variables to determine if they were normally distributed, and we used natural logarithmic transformation for hepatic enzymes since they were not normally distributed. Independent-samples t test for continuous variables and Chi-squared for categorical ones were used for univariate unadjusted analyses. Analyses of covariance were used to compare adjusted means (age, sex, education, body mass index, and total pack years of smoking). To further analyze the effects of amount of alcohol consumed in the past 30 days, current drinkers of both races were divided into tertiles. Differences in hepatic enzyme levels among the covari-ates-adjusted tertiles were analyzed between the two racial groups using general linear models.

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