ALCOHOL INTAKE AND INCIDENCE OF CORONARY DISEASE IN AUSTRALIAN ABORIGINES

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1 Alcohol & Alcoholism Vol. 42, No. 1, pp , 2007 Advance Access publication 22 November 2006 doi: /alcalc/agl093 ALCOHOL INTAKE AND INCIDENCE OF CORONARY DISEASE IN AUSTRALIAN ABORIGINES V. BURKE 1 *, A. H. LEE 2, E. HUNTER 3, R. SPARGO 4, R. SMITH 5, L. J. BEILIN 1 and I. B. PUDDEY 1 1 University of Western Australia, School of Medicine and Pharmacology, Royal Perth Hospital Unit, 2 School of Public Health, Curtin University of Technology, 3 School of Population Health, University of Queensland, 4 Puntukurnu Aboriginal Medical Service, Pilbara Region, Western Australia and 5 Miln Walker and Associates Pty Ltd, PO Box 167, Belair, South Australia (Received 5 October 2006; first review notified 8 October 2006; in revised form 25 October 2006; accepted 28 October 2006; advance access publication 22 November 2006) Abstract Aims: To examine risk for coronary heart disease (CHD) and cardiovascular disease (CVD) in relation to alcohol in a cohort of Australian Aborigines. Methods: In , alcohol intake, drinking pattern, and beverage preference were elicited by interviewer-administered questionnaire in Western Australian Aborigines (258 men and 256 women) and cardiovascular outcomes ascertained through linkage to mortality and hospital admission records to Results: In proportional hazards models, risk for CHD, relative to lifetime abstainers, was significantly increased in ex-drinkers [Hazard ratio (HR), 2.29; 95% confidence intervals (CI), ], those drinking g/day in men or g/day in women (HR 2.80; 95% CI, ) and those drinking >150 g/day for men or >100 g/day for women (HR, 2.25; 95% CI, ) with a J-shaped relationship. Low-to-moderate drinkers had lower waist girth, exercised more and had a lower prevalence of overweight and smoking than at-risk drinkers. A preference for wine was associated with lower HR (0.28; 95% CI, ). With CVD, only ex-drinkers showed significantly increased risk (HR, 1.87; 95% CI, ). Conclusions: More favourable health-related behaviours in low-to-moderate drinkers suggest that lower risk could be mediated by lifestyle, as proposed in other populations. INTRODUCTION Epidemiological studies suggest that light-to-moderate alcohol intake may be protective against coronary heart disease (CHD) (Gronbaek, 2002), a finding supported by meta-analyses (McClure, 1993; Corrao, et al., 2000). A U-or J-shaped relationship between coronary endpoints and alcohol intake is recognized (Marmot and Brunner, 1991; Murray et al., 2002). However, this association has not been observed in all populations (Hart et al., 1999; Fuchs et al., 2004). Differences between populations may relate to drinking patterns, with binge drinkers at greater risk of coronary events (McElduff and Dobson, 1997), beverage type, with possible benefits of wine-drinking (Klatsky et al., 2003), and to lifestyle factors (Ruidavets et al., 2004). Such associations have not been examined in Australian Aborigines, in whom, relative to the non-aboriginal population, drinking alcohol at harmful levels is more common (Ministerial Council on Drug Strategy, 2001), and risk of death from cardiovascular disease has increased at least 3-fold (National Health and Medical Research Council, 2000). Detailed information about patterns of drinking, alcohol intake and beverage preference was recorded in from a cohort of Aboriginal people in the Kimberley region of Western Australia (Hunter et al., 1991, 1992), along with measurement of blood pressure (BP), blood lipids and anthropometry. Cross-sectional analysis at that time showed a rate of hypertension, defined according to cut-off points of 160/95 mmhg, almost three times that of non-aboriginal Australians (Smith et al., 1992a). Examination of long-term outcomes in this cohort became possible with the establishment of the Western Australian Data Linkage System in 1995 (Holman et al., 1999), providing access to hospital and death records. We now report associations between alcohol intake, drinking *Author to whom correspondence should be addressed at: School of Medicine and Pharmacology, Royal Perth Hospital Unit, Box X2213 GPO, Perth 6847, Australia. Tel.: ; Fax: ; vburke@ cyllene.uwa.edu.au pattern and beverage preference determined in the initial survey and endpoints for CHD and cardiovascular disease (CVD) over a 13 year follow-up period. POPULATION AND METHODS Cardiovascular risk factors and lifestyle, including details of usual alcohol consumption, were recorded in in a cohort of Aborigines, aged between 15 and 88 years, in the Kimberley region of Western Australia (Smith et al., 1992b). Individuals were randomly selected in an age- and genderstratified sample from the Community Health Client Register of the Health Department of Western Australia in January 1987 as previously described (Smith et al., 1992a). The Commonwealth Scientific and Industry Research Organisation (CSIRO, Australia) and the Health Department of Western Australia gave ethical approval. All participants provided individual consent (Smith et al., 1992a). Questionnaires and measurements Interviewer-administered questionnaires provided information about demographics including usual place of residence classified according to ease of access to alcohol (very-hard-to-get, hard-to-get or easy-to-get). Alcohol intake and preference for beer, wine or spirits were also elicited by an intervieweradministered questionnaire, validated by comparison with sales figures in the community, correlation with measurement of g glutamyl-transpeptidase (GGT) activity, and other information within the community. Participants were categorized into those who had never drunk alcohol, ex-drinkers, those who drank on most days of the week, those who drank intermittently at intervals of not >2 weeks and episodic drinkers who drank at intervals >2 weeks. The amount of alcohol consumed over 48 h was determined using a contextualized diary of the last two drinking periods and the volume was converted to grams of alcohol per drinking day. Drinkers were then grouped according to alcohol intake: <40 g/day men, <20 g/day women; g/day men, g/day 49 Ó The Author Published by Oxford University Press on behalf of the Medical Council on Alcohol. All rights reserved

2 50 V. BURKE et al. women; g/day men, g/day women; g/ day men, g/day women; >150 g/day men, >100 g/day women. For ex-drinkers, reasons for giving up alcohol were recorded at interview. All interviews (E.H.) and physical examinations (R.S.) were undertaken by the same study personnel. Smoking habits were recorded and the amount of physical activity was assessed by three questions that asked about the frequency (3 times a week, once or twice a week, about once a month, rarely or never) of exercise. Blood pressure and anthropometry BP was measured using a Dinamap oscillometric monitor (Johnson and Johnson, Sydney) as described previously (Smith et al., 1992a). An initial measurement of BP was taken (15 min after entry) and 5 min after familiarization, BP was measured in triplicate at 1 min intervals and the mean of the last two was used in analysis. Weight was recorded using a Portable Field Scale Model MPS 120, calibrated daily, and height with a stadiometer (Harpenden Survey Set, CMS Weighing Equipment, London). Data linkage and diagnosis coding Participants were linked to hospital, cancer and death records from 1988 to 2000 by the Western Australian Data Linkage Unit. Ethical approval was obtained from the Western Australian Aboriginal Health Information and Ethics Committee, the University of Queensland Health Ethics Committee, and the Kimberley Aboriginal Medical Services Council. While linkage used for all available information, only de-identified data were used subsequently. Diagnoses were coded from hospital separation records and death records in the period using the ICD-9-CM (National Coding Centre, 1995) and from 1999 to 2000 using the ICD-10-AM (National Centre for Classification in Health, 2000). Mapping of ICD-10-AM codes to ICD-9-CM codes was carried out using software developed by the National Centre for Classification in Health. Cardiovascular disease (CVD) included the following ICD-9-CM codes: 391, , , 410, 411, , , Coronary heart disease (CHD) comprised the codes Diagnosis codes were included if they appeared in any of 21 diagnosis fields. Statistical methods CHD endpoints included mortality and a first admission to hospital with CHD; endpoints for CVD combined mortality from CVD and a first admission to hospital with CVD. Time to event was calculated from January 1, 1988 with a censoring date of 31 December Endpoints were examined using proportional hazards models in Stata (Statcorp, Texas) or SPSS (SPSS, Chicago, Ill). All models were adjusted for age, using a Box Tidwell transformation (Hosmer and Lemeshow, 2000), and gender, as well as for the type of community classified according to ease of access to alcohol. Generalized linear models, with adjustment for gender, were used in comparing risk factors as continuous variables according to drinking categories. c 2 -tests were used for categorical variables that included body mass index (BMI) classified according to the cut-off point of 22 kg/m 2, as recommended for Aboriginal people (Daniel et al., 2002). P-values < 0.05 were considered significant. RESULTS Characteristics of the population at baseline and lifestyle factors are shown in Tables 1 and 2. During follow-up from 1988 to 1989 to the end of 2002 there were 13 deaths from CHD among women and 11 among men; 55 women and 51 men had a first hospital admission for CHD recorded in this interval. For CVD there were 22 deaths and 97 first hospital admissions among women and 24 deaths and 91 first hospital admissions among men. Follow-up of participants was done for a mean of 11.6 years. Among drinkers, only 8 (8%) women and 13 men (8%) had an alcohol intake within the Australian national guidelines of not more than an average of four standard drinks daily for men and two for women (National Health and Medical Research Council, 2001). Among drinkers, 83% of men drank at least 60 g/day of alcohol while, among women, 82% exceeded 40 g/day. Alcohol intake ranged from 7 to 266 g/day in women and from 7 to 647 g/day in men; 76% of women and 84% of men preferred beer; only 1 woman and 5 men chose low-alcohol beer. Wine was preferred by 17% of women and 14% of men, and spirits by 6% of women and 2% of men. Coronary heart disease As shown in Table 3, in models adjusted for age, gender and type of community, risk of mortality or morbidity for CHD was significantly greater among ex-drinkers (P = 0.032) and in the highest category of alcohol intake (>150 g/day for men, >100 g/day for women), relative to lifetime abstainers Table 1. Characteristics of the population at entry to the survey Variable a Men (N) Women (N) Men Women Age group (years) [n (%)] (11) 22 (9) (17) 43 (18) (17) 40 (17) (16) 43 (18) (16) 40 (17) (17) 36 (15) >70 15 (6) 16 (7) Seated SBP (mmhg) (21) 137 (24) Seated DBP (mmhg) (14) 81 (14) Heart rate (beats/min) (14) 84 (14) Weight (kg) (14.5) 65.5 (17.1) BMI (kg/m 2 ) (4.4) 25.9 (6.7) Waist girth (cm) (12.7) 94.4 (15.9) Cholesterol (mmol/l) (1.3) 5.4 (1.3) HDL-cholesterol (mmol/l) a (0.42) 1.27 (0.37) Hypertensionb [n (%)] (44) 88 (37) Diabetes [n (%)] (4) 11 (4) a Continuous variables are presented as mean (SD). Discrete variables are shown as numbers (%). b SBP >140, DBP >90 or on treatment for hypertension.

3 ALCOHOL AND CORONARY DISEASE IN ABORIGINES 51 Table 2. Lifestyle characteristics in men and women at baseline Variable Men (N) Women (N) Men [n (%)] Women [n (%)] Alcohol drinking a Lifetime abstainers 22 (9) 109 (42) Ex-drinkers 65 (26) 53 (21) <40 g/day men, <20g/day women 13 (5) 8 (3) g/day men, g/day women 13 (5) 10 (4) g/day men, g/day women 56 (22) 29 (11) g/day men, g/day women 25 (10) 14 (6) >150 g/day men, >100 g/day women 62 (24) 35 (14) Drinking pattern b Daily drinkers 53 (31) 21 (22) Episodic drinkers 56 (33) 38 (39) Intermittent drinkers 60 (36) 38 (39) Alcohol intake in drinkers (g/day) c ( ) 90 ( ) Beverage preference (geometric mean and 95% CI) Beer ( ) 77.3 ( ) Wine ( ) 59.4 ( ) Spirits ( ) 43.4 ( ) Drinking pattern b Daily drinkers ( ) 83.9 ( ) Episodic drinkers ( ) 56.3 ( ) Intermittent drinkers ( ) 81.7 ( ) Smoking Never smokers 59 (28) 97 (42) Ex-smokers 8 (4) 5 (2) Current smokers 127 (65) 61 (37) Any exercise d A least three times a week 15 (6) 31 (13) Once or twice a week 70 (28) 57 (24) Once a month 9 (4) 7 (3) Rarely or never 81 (32) 69 (29) a Determined as the average of the last two drinking days. b Daily drinkers alcohol on most days of the week. Episodic drinkers alcohol at intervals of >2 weeks. Intermittent drinkers alcohol for a few days at least every 2 weeks. c Average alcohol intake per 24 h on drinking day (geometric mean and 95% CI). d Activities such as walking, gardening, swimming. Table 3. HRs and 95% CI with coronary disease as the endpoint Alcohol category Model 1 95% CI Model 2 95% CI Model 3 95% CI Lifetime abstainers Ex-drinkers <40 g/day men, <20 g/day women g/day men, 21 40g/day women g/day men, g/day women g/day men, g/day women >150 g/day men, >100 g/day women Coronary disease includes death or a first hospital admission for ICD-9 codes HRs are derived from proportional hazards models. Model 1 is adjusted for age, gender and accessibility to alcohol. Model 2 is additionally adjusted for the classical risk factors of cholesterol, central obesity and mean arterial pressure. Model 3 includes these variables with the addition of smoking (current smokers, non-smokers and ex-smokers) and exercise (takes any exercise at least weekly). (P = 0.045). Further adjustment for the classical risk factors of cholesterol, blood pressure, and waist girth showed significantly increased risk in ex-drinkers (P = 0.009), those drinking up to 60 g/day in men and 40 g/day in women (P = 0.041) and in the highest drinking category (P = 0.042). With the inclusion of smoking habits and exercise in the models, statistically increased risk persisted in ex-drinkers (P = 0.011) and those drinking up to 60 g/day in men and 40 g/day in women (P = 0.027). While ratios are not statistically significant for all categories, there is, overall, a pattern consistent with a J-shaped relationship between category of alcohol intake and risk of cardiovascular disease. Cardiovascular disease Table 4 shows the hazard ratios (HRs) and 95% confidence intervals (CI) with CVD as the endpoint. Relative to lifetime abstainers, the only category showing a statistically significant increase in risk was the ex-drinkers. No pattern suggesting lower risk in light-to-moderate drinkers was seen with CVD as the endpoint. Associations with beverage type and drinking pattern In models adjusted for age, gender and community type, excluding non-drinkers, and including amount of alcohol

4 52 V. BURKE et al. Table 4. HRs and 95% CI with cardiovascular disease as the outcome Alcohol category Model 1 95% CI Model 2 95% CI Model 3 95% CI Lifetime abstainers Ex-drinkers <40 g/day men, <20 g/day women g/day men, 21 40g/day women g/day men, g/day women g/day men, g/day women >150 g/day men, >100 g/day women Cardiovascular disease includes ICD-9-CM codes 391, , , 410, 411, , and Hazard ratios are derived from proportional hazards models. Model 1 is adjusted for age, gender and accessibility to alcohol. Model 2 is additionally adjusted for the classical risk factors of cholesterol, central obesity and mean arterial pressure. Model 3 includes these variables with the addition of smoking (current smokers, non-smokers and ex-smokers) and exercise (plays sport, takes vigorous exercise or any other exercise at least weekly). intake, pattern of drinking was not a significant predictor of CHD endpoints. The HR for intermittent and episodic drinkers relative to daily drinkers was 1.09 (95% CI, ). There was, however, a statistically significant association with beverage preference, independent of drinking pattern and amount of alcohol consumption. The few participants who preferred spirits were excluded from these models because of problems with convergence if they were included. With a preference for beer as the reference category, the HR associated with a preference for wine-drinking was 0.28 (95% CI, ). The inverse association of CHD with wine-drinking remained statistically significant after adjustment for cholesterol, BP, waist girth, smoking habits and exercise [ relative risk (RR), 0.22; 95% CI, ]. With CVD as the outcome, there were no statistically significant associations with drinking pattern or beverage preference. Lifestyle variables associated with category of alcohol intake and beverage preference Participants were categorized as lifetime abstainers, exdrinkers, safe drinkers who did not exceed guidelines for alcohol consumption and at-risk drinkers who exceeded these guidelines. There was a significant between-group difference for waist girth, adjusted for gender (P = 0.002) with greatest mean values in the abstainers (93.1; 95% CI, ) and ex-drinkers (94.6; 95% CI, ) with a mean of 84.4 (95% CI, ) in safe drinkers and 89.8 (95% CI, ) in at-risk drinkers. BMI exceeded 22 kg/m 2 in 89 abstainers (74%), 84 ex-drinkers (74%), 11 safe drinkers (48%), and 143 at-risk drinkers (60%) (P = 0.003). Among abstainers 11 (9%) played sport at least weekly, compared with 5 ex-drinkers (5%), 5 safe drinkers (23%) and 36 at-risk drinkers (16%) (P = 0.007). Current smokers comprised 14 abstainers (12%), 33 ex-drinkers (31%), 8 safe drinkers (35%), and 127 at-risk drinkers (60%) (P < 0.001). Preference for wine or beer was not significantly related to waist girth (mean 89.3 cm; 95% CI, in wine drinkers; 88.6 cm; 95% CI, in beer drinkers; P = 0.925), in the prevalence of BMI >22 kg/m 2 (59 versus 58%, respectively, P = 0.886), exercise at least once a week (13 versus 16%, P = 0.649), or smoking habits (63% current smokers versus 56%, P = 0.417). No dietary data were available at the time of these analyses. DISCUSSION This analysis has confirmed the higher risk of both CHD and CVD in ex-drinkers while, for CHD, the pattern of risk is consistent with a J-shaped association with alcohol consumption, the lowest risk being in the small group of participants drinking at low-to-moderate levels. We also found a significantly lower risk of CHD in wine drinkers, independent of drinking pattern and the amount of alcohol consumed. Our finding of significantly increased risk for both CHD and CVD in ex-drinkers is consistent with previous studies (Wannamathee and Shaper, 1997) and is likely to be explained, as suggested, by pre-existing illness; 31% of exdrinkers in this Aboriginal cohort indicated that they stopped drinking for health reasons. Overall there was a pattern of increased risk for CHD associated with drinking at higher levels with the lowest risk in the group drinking at safe levels (National Health and Medical Research Council, 2001), consistent with a J-shaped relationship as reported in other populations (Corrao et al., 2000). However, drinking behaviour in this Aboriginal population is very different from that in other populations in which such a relationship has been reported. Australian Aborigines are less likely to drink alcohol than non-aboriginal Australians but among those who do drink alcohol, consumption at hazardous levels is common (McClennan and Madden, 2003). Among our cohort, there was a preponderance of drinkers who consumed very high levels of alcohol; an intake of >60 standard drinks per drinking day was recorded among a small group of extreme binge drinkers. Numbers were small in some categories of lower alcohol intake. For these reasons, comparison with other populations must be interpreted cautiously. Not only does the pattern of alcohol intake among Aborigines differ from that in other populations where alcohol intake and risk of CHD has been examined, other lifestyle behaviours differ widely from those in non-aboriginal Australians. Lifestyle diseases are common, with a rapidly increasing rate of obesity and diabetes, associated with replacement of a traditional diet by one high in fat and low in fibre, and lack of physical activity (McClennan and Madden, 2003). In addition, an estimated 51% of Aborigines over the age of 18 years are smokers compared with 24% of non-aboriginal Australians (McClennan and Madden, 2003). Risk is increased further by the prevalence of individuals with multiple risk factors in the Aboriginal population (McClennan and Madden, 2003).

5 ALCOHOL AND CORONARY DISEASE IN ABORIGINES 53 Lifestyle characteristics, rather than the effects of the amount of alcohol consumed, have been suggested to explain the lower risk of CHD among individuals with low-tomoderate alcohol intake (Herberth et al., 1988; Fuchs et al., 2004; Ruidavets et al., 2004), and may be confounders in population studies that examine associations between alcohol intake and CHD (Fuchs et al., 2004). In our study, those drinking at safe levels had lower waist circumference, fewer were overweight, more participants played sport at least weekly and the prevalence of smoking was almost half that seen in at-risk drinkers. However, the small number of participants in the safe-drinking group limits the validity of such inferences. A preference for wine has also been reported to be associated with lower risk of mortality, possibly explained by drinking pattern, constituents of wine other than alcohol, or lifestyle characteristics (Burke et al., 1995; Tjonneland et al., 1999; Klatsky et al., 2003; Ruidavets et al., 2004). In our Aboriginal cohort there were no statistically significant associations between lifestyle variables and a preference for wine but associations with other lifestyle factors such as diet cannot be excluded. Our observation of a lower risk of CHD in Aboriginal wine preferrers is unexplained. Drinking pattern may also influence risk for CHD (Tolstrup et al., 2004) and a greater risk of CHD in binge drinkers has been reported (Murray et al., 2002). In our Aboriginal cohort drinking pattern did not significantly predict risk of CHD or CVD independent of amount of alcohol consumed. The inclusion of beverage preference in these models did not affect interpretation. With CVD as the endpoint we found no indication of a J-shaped association with alcohol intake. Only ex-drinkers had a statistically significant increased risk of CVD. Klatsky et al. (1990) reported differences in associations between alcohol consumption and diagnoses included within CVD. In that study, alcohol intake was associated with higher risk of mortality from hypertension and stroke, but lower risk from CHD, while ex-drinkers had higher rates for CVD mortality, consistent with our findings. Our study utilizes a unique dataset that links use of alcohol to CHD and CVD in the long-term among Aboriginal Australians. Although the length of follow-up is a strength of the study, this also leads to limitations. All data documenting lifestyle and alcohol intake were obtained up to 13 years before the present analysis. Misclassification arising from changes in alcohol use over that period could obscure relationships with endpoints. Errors in documenting alcohol intake, beverage preference, and patterns of drinking would also affect interpretation of models. While all data were obtained by interviewers experienced in communicating with Aboriginal Australians and reported alcohol intakes were validated with reference to sales of alcohol in the community and GGT activity, there remains the potential for misclassification. This may be relevant to the lack of a statistically significant association with drinking pattern in our analysis, for example. While the number of events is relatively small, no other set of data links long-term outcomes with detailed information about alcohol consumption in individual Australian Aborigines. In this Aboriginal cohort, a group with greater risk of CHD and higher rates of hazardous drinking than non-aboriginal Australians, risk for CHD was increased in ex-drinkers and showed a pattern consistent overall with a J-shaped association with alcohol intake. 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