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, telepho ne interviews generally yield higher coverage rates, have a lower proportio n of missing values and result in fewer inconsistencies. Meta-analyses, how ever, show that responses to sensitive questions by telephone tend to be bi ased by social expectations. The aim of the study is to examine whether res ponses on alcohol consumption and alcohol-related problems differ with resp ect to mode of administration (self-administered vs. telephone). Design and participants. Data were analysed from the 1995 self-administered survey am ong 6427 subjects and from telephone surveys conducted annually between 199 4 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 i nto pure alcohol (ethanol) per day and categorized into no alcohol consumpt ion (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 u sing the CAGE questionnaire with a cut-off point of at least two positive r esponses. Findings. Using (cumulative) logistic regression, a significant m ode effect was found for both alcohol consumption and alcohol-related probl ems. Lower beverage-specific prevalences in the telephone mode were found t o be responsible for the difference in the distribution of the summary cons umption measure. Conclusions. Results indicate that patterns of drinking an d alcohol-related problems are more easily reported in self-administration questionnaires compared to telephone interviews.