Colestipol-Niacin Therapy and Coronary Atherosclerosis

To the Editor.—  The report entitled "Beneficial Effects of Combined Colestipol-Niacin Therapy on Coronary Atherosclerosis and Coronary Venous Bypass Grafts"1 must be interpreted with caution, for the following reasons:Although the study population consisted of nonsmoking men 40 to 59 years of age with progressive atherosclerosis, of whom 28 of the 94 men in the treatment group and 30 of the 94 men in the placebo group had never smoked, the lifetime smoking experience of the many study subjects who had smoked is not presented²; also, we are not told how many heavy smokers with substantial cardiovascular disease quit smoking as they were joining the study. If so, their recession from smoking-induced cardiovascular damage may have been misinterpreted to give spurious credit to coincident drug intervention. The number of never-smokers studied is too few to provide a dependable measure of the effects of drug treatment independent of ex-smokers.Furthermore, the