Data on alcohol drinking is unreliable There are two major limitations in the data collected relating to alcohol drinking patterns in this study.
The first is collecting information on what people eat and drink is notoriously unreliable. And even more of a problem is the extent of this misreporting tends to vary considerably between people, making it very difficult to correct for.
The second major limitation was the researchers collected data on alcohol drinking patterns at the beginning of this longitudinal study and extrapolated forward many years to complete the analysis.
That is, researchers looked at drinking patterns at the start of the study and assumed people had the same drinking patterns for the whole study.