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Patterns of drinking and estimates of alcohol-related mortality in New Zealand.

Article Excerpt
The effect of drinking pattern, independent of average volume of alcohol consumption, is increasingly recognized as an important determinant of the impact of alcohol on health (Rehm et al. 2001; Room et al. 2003; Bobak et al. 2004; Russell et al. 2004; Tolstrup et al. 2004). The same weekly alcohol consumption can result from one to two drinks per day with dinner or ten drinks every Friday night, but the impact on disease and injury risk is different. This effect of drinking pattern on health is largely mediated through the adverse effect of intoxication on injury risk, and the beneficial effect of low volume frequent alcohol intake on coronary heart disease (CHD) (Rehm et al. 2003b; Rehm et al. 2004).

In the Global Burden of Disease Study the lack of individual level data on the impact of pattern of drinking on health outcomes led to aggregate level analyses where the mediating influence of pattern of drinking on volume for coronary heart disease and injury mortality was modeled in 80 countries (Gmel et al. 2001; Gmel et al. 2003; Rehm et al. 2004). In these analyses a simple classification of pattern of drinking at a country level by WHO was used (Rehm et al. 2003a). This enabled a country's prevailing drinking pattern to modify the estimates of alcohol-related burden of coronary heart disease and injury, and thus the balance of health risks and benefits of alcohol.

When estimating the alcohol-related health burden in a single country, differences in drinking patterns between subpopulations are also likely to have a substantial effect on estimates of harms and benefits. In the recent New Zealand study of the burden of death, disease, and disability due to alcohol in 2000 (Connor et al. 2005), the difference in average drinking pattern between the indigenous Maori population and the non-Maori New Zealand population was considered when estimating health effects of alcohol but, due to lack of reliable local data, some assumptions about the extent and effects of the pattern differences were necessary.

In 2000, Maori comprised approximately 15% of the New Zealand population. Maori have a special relationship with the Crown as "tangata whenua" (people of the land), in recognition of the Treaty of Waitangi. Reducing inequalities in health status and Maori development in health are goals of the New Zealand Health Strategy (Ministry of Health 2000).

This article compares estimates of the health burden of alcohol in New Zealand as a whole with analyses that incorporate the differences in pattern of drinking between Maori and non-Maori.

Methods

We used and adapted methods that were developed by the WHO for measuring the impact of important risk factors on health globally CRA (Rehm et al. 2004). Further details of our methods are available (Connor et al. 2005). A disaggregated approach was taken to estimating the mortality and years of life lost due to alcohol consumption. For each health condition that had an established relationship with alcohol, the magnitude of the risk or benefit at different levels of alcohol consumption was clarified from the epidemiological literature. A list of the conditions that were included is given in Table 1. The average levels of alcohol consumption in Maori and non-Maori populations for each age and sex group, were identified from the best available survey data (Habgood et al. 2001; McLeod et al. 2002; Barnes et al. 2003). For most conditions these exposure data were combined with the estimates of alcohol-disease relationships, to calculate how much of each alcohol-related condition was attributable to alcohol (the alcohol-attributable fraction, or AAF).

The estimation of AAFs for coronary disease and injuries were considered separately due to evidence that pattern of drinking, as well as, average volume of drinking in determining the effects of alcohol on these conditions.

We used the pattern of drinking categories developed by WHO, based on evidence about average harmful and beneficial effects of different alcohol consumption patterns in populations worldwide (Rehm et al. 2003a), to classify the average drinking patterns of Maori and non-Maori populations. Usually applied at a country level, the categories are determined by scoring men and women according to the proportion that drinks daily, the frequency of getting drunk, usual drinking quantity per session, fiesta binge drinking, drinking with meals, and drinking in public places. Alcohol consumption in New Zealand had been classified by WHO as Pattern 2 of four possible patterns, where Pattern 1 is the most beneficial and Pattern 4 is the most detrimental (Rehm et al. 2004). Based on these criteria, and information from the National Alcohol and Te Ao Waipiro surveys...