Measuring alcohol consumption and alcohol-related problems: comparison of responses from self-administered questionnaires and telephone interviews

Aims. Compared with surveys using self-administered questionnaires, telephone interviews generally yield higher coverage rates, have a lower proportion of missing values and result in fewer inconsistencies. Meta-analyses, however, show that responses to sensitive questions by telephone tend to be biased by social expectations. The aim of the study is to examine whether responses on alcohol consumption and alcohol-related problems differ with respect to mode of administration (self-administered vs. telephone). Design and participants. Data were analysed from the 1995 self-administered survey among 6427 subjects and from telephone surveys conducted annually between 1994 and 1996 yielding a pooled sample of 6193 subjects. Measurements. Alcohol consumption within the last 30 days was measured using a beverage-specific quantity-frequency index. For a summary measure responses were converted into pure alcohol (ethanol) per day and categorized into no alcohol consumption (0 g), non-hazardous consumption (less than or equal to 20 g for female and less than or equal to 40 g for males) and hazardous consumption (>20 g for females and >40 g for males). Alcohol-related problems were assessed using the CAGE questionnaire with a cut-off point of at least two positive responses. Findings. Using (cumulative) logistic regression, a significant mode effect was found for both alcohol consumption and alcohol-related problems. Lower beverage-specific prevalences in the telephone mode were found to be responsible for the difference in the distribution of the summary consumption measure. Conclusions. Results indicate that patterns of drinking and alcohol-related problems are more easily reported in self-administration questionnaires compared to telephone interviews.