Measuring average alcohol consumption: the impact of including binge drinks in quantity-frequency calculations.

AIMS: Average daily alcohol consumption is usually calculated based on self-reports of the quantity (number of drinks consumed per drinking-day) and frequency (number of drinking-days) of alcohol consumption within a given time period. However, this method may underestimate average daily alcohol consumption (and in turn, the prevalence of heavy drinking), because studies demonstrate that respondents do not typically include binge drinking occasions in estimates of their 'usual' or 'average' daily alcohol consumption.
DESIGN: We used the Behavioral Risk Factor Surveillance System (BRFSS), an annual random-digit telephone survey of US adults aged 18 years or older, to estimate average daily alcohol consumption using standard quantity-frequency questions, and then recalculated this measure by including self-reports of binge drinking. The proportion of respondents who met a standard, sex-specific definition of heavy drinking based on average daily alcohol consumption was then assessed nationally and for each state.
FINDINGS: Compared to standard quantity-frequency methods, including binge drinks in calculations of average daily alcohol consumption increased the relative prevalence of heavy drinking among all adults by 19% to 42% (depending on the method used to estimate the number of drinks per binge). Among binge drinkers, the overall prevalence of heavy drinking increased 53% relative to standard quantity-frequency methods. As a result, half of women binge drinkers and half of binge drinkers aged 55 or older met criteria for heavy drinking.
CONCLUSIONS: Including binge drinks (especially the application of age- and sex-specific estimates of binge drinks) in the calculation of average daily alcohol consumption can improve the accuracy of prevalence estimates for heavy drinking among US adults, and should be considered to increase the usefulness of this measure for alcohol surveillance.