To me that seems fine, although loosing some granularity compared to continuous variable. Say there were four people, and they smoked 1, 2, 3, 4 cigarettes, respectively, or, you can say, they smoked little, moderate, many, and very many cigarettes, that would still be four quartiles. However, if you define 2-3 cigarettes as moderate, now we cannot have four quartiles anymore with categories, because two people will belong to moderate category. So the key here is, before you create categories of the categorical variable, to look at the rank boundaries of sorted continuous variable, so you can partition the categories neatly and there are really four quartiles of more or less equal size.
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