As far as we know, there are no studies performed in
which subgroups with elevated clustering were de-
fined. Although we can only speculate, a possible underlying
factor in the strong relationship between
smoking and alcohol consumption in the youngest age
group may be the degree of self-consciousness, which is
generally higher in younger adults. It is, however, dif-
ficult to explain the higher tendency of clustering between
two risk habits in subjects who perceive their
health as very good or excellent (with the exception of
alcohol and fruit/vegetable consumption). Maybe subjects
who believe their health is excellent do not directly
experience the risks associated with an unhealthy
lifestyle.