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Exercise and lipoprotein levels.

Exercise and Lipoprotein Levels To the Editor: I recently reviewed the data and conclusions in the article by Brownell et al. The authors indicate that their data show moderate exercise to have "different effects on men and women" with respect to lipoprotein levels. Their results fail to support this conclusion; rather, they suggest that men and women have similar lipoprotein responses to exercise. The authors' data show that the male and female groups did not begin the investigation with comparable lipoprotein levels. Women had substantially lower mean levels of cholesterol (186.8 vs 207 mg/dl), lowdensity lipoprotein (LDL) cholesterol (111.8 vs 132.8 mg/dl), and triglycerides (71.5 vs 176.4 mg/dl). The women also demonstrated substantially higher values of mean high-density lipoprotein (HDL) cholesterol (58.6 vs 42.2 mg/dl) and HDL/LDL cholesterol ratio (0.572 to 0.351). The authors' data (tables 1 and 2) report similar changes in levels of cholesterol (both significantly decreased), HDL cholesterol (no significant change), and LDL cholesterol (no significant change) in both men and women after 10 weeks of training. When the male and female data are combined, rather than obscuring these important differences (table 3) as the authors suggest, the combination affirms the similarity of their responsiveness. Separately, neither male nor female groups reported significant decreases in LDL cholesterol levels. Only when male and female data were combined was a statistical decrease in LDL cholesterol level reached. If the lipoprotein response to exercise was dissimilar in males with regard to females, we would not expect a combination of these two groups to result in a significant change, as neither group generated statistical significance when analyzed separately. The authors do report differences in the percent of lipoproteins in men compared with women. However, the concluding remarks that plasma lipoprotein "levels" improve much more in men than women is not supported. "Percent change" may be dissimilar between the male and female groups, but that is more likely a function of initial lipid values rather than a real difference. For example, the women would have to increase their HDL cholesterol level 1.38 mg/dl for every l-mg/dl increase demonstrated by the men in this study to show an equivalent percent change. This would be necessary even though women began this exercise study with an HDL cholesterol level more than 38.8% higher than men. Clearly, the percent change in these two dissimilar groups cannot accurately measure the lipoprotein response to exercise. In summary, the level of response among both male and female groups were similar. Combining the data appears to enhance this parity of response rather than obscure their dissimilarity. Both men and women displayed comparable changes in lipoprotein levels after 10 weeks of exercise training. LINN GOLDBERG, M.D. Oregon Health Sciences University Portland, Oregon