Latent class profile analysis: an application to stage-sequential process in early-onset drinking behaviours.

Earlier age of drinking is a well-known predictor for a variety of adverse public health consequences in the United States and worldwide. In longitudinal research on early-onset drinkers, a great deal of attention has been paid to the identification of subgroups of individuals who follow similar sequential patterns of drinking behaviours. However, research on the sequential development of drinking behaviour can be challenging in part because it may not be possible to directly observe the particular drinking behaviour stage at a given point in time. To address this difficulty, one can use a latent class analysis (LCA) approach, which provides a set of principles for the systematic identification of homogeneous subgroups of individuals. We apply an LCA approach in an investigation of stage-sequential patterns of drinking behaviours among early-onset drinkers from early to late adolescence, using data from the 'National Longitudinal Survey of Youth 1997.' In this work, an identification procedure is used to sort different patterns of drinking behaviours into a small number of classes, based on responses to questions about drinking at each measurement occasion; with class assignment, next the class sequencing of early-onset drinkers over the entire set of time points is evaluated in order to identify two or more homogeneous subgroups. A condition to be satisfied is that all early-onset drinkers in a subgroup should exhibit a similar sequence of class memberships over time. This approach uncovers four common drinking behaviours in early-onset drinkers over three measurements from 1997 through 2003. The sequences of drinking behaviours can be grouped into three groups of sequential patterns representing the most probable progression of early-onset drinking behaviours.