Estimating levels and trends in alcohol use – investigating the validity of estimates based on Norwegian population surveys

Estimates of alcohol use from a series of cross-sectional face-to-face surveys, conducted by Synovate Norway on behalf of the Norwegian institute for alcohol and drug research during the 1990s and 2000s (the Substance Use Surveys, SUS), are compared with registered sales statistics of alcohol and estimates of alcohol use from Statistics Norway’s Health Surveys (HS). The results show that SUS estimates of levels and trends in alcohol use are in conflict with these alternative data sources, also when standard adjustment strategies (using poststratification weights, controlling for background characteristics in regressions) are used. We conclude that there is likely selection on alcohol use and other factors into the SUS samples, to a higher degree than in the HS samples, which renders standard estimates of alcohol use from SUS data unreliable. In fields such as substance use research, it is notoriously difficult to measure the phenomena we are interested in, and it is especially important to assess the validity of the survey estimates with data from alternative sources