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 (< or = 20 g for female and < or = 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.