ENVIRONMENTAL AND BEHAVIORAL-INFLUENCES ON PLASMA LIPOPROTEIN(A) CONCENTRATION IN WOMEN TWINS

Background. Genetic factors are firmly established as determinants of plasma lipoprotein(a) [Lp(a)] concentration. This study focused on beh avioral or environmental factors that might also explain some of the v ariation in levels of this cardiovascular disease risk factor. Methods . The study considers the 644 women twins (597 whites, 47 blacks; ages 30-91 years) who participated in the second examination of the Kaiser Permanente Women Twins Study. Cross-sectional associations of behavio rs and environmental factors with Lp(a) concentration were studied bef ore and after removing genetic influences on Lp(a) levels. Results. Lp (a) levels were substantially higher among blacks than whites (P < 0.0 001). The distribution of apo(a) size phenotypes also differed between blacks and whites, but this variation did not explain the difference in Lp(a) levels. A positive association of Lp(a) concentration with ag e was noted among blacks (P = 0.06) but not among whites (P = 0.86). N o evidence was found for associations of Lp(a) with menopausal status, cigarette smoking, alcohol consumption, total or heavy recreational p hysical activity, 11-year weight gain, use of several antihypertensive medications, or diabetes status in either race. Among postmenopausal women, however, estrogen replacement therapy was associated with lower Lp(a) levels among whites (7.9 vs 9.9 mg/dl, P = 0.05). Removing gene tic variation in Lp(a) concentration by matching 171 monozygotic (MZ) twins to their genetically identical co-twins did not alter these find ings. Conclusion. The plasma concentration of Lp(a), unlike other lipo protein risk factors for heart disease, has few behavioral or environm ental correlates, at least among white women. Neither behavioral or en vironmental factors nor variation in the apo(a) size phenotype appeare d to explain the higher mean Lp(a) levels among black compared with wh ite women; further study seems warranted in larger samples of black wo men. (C) 1994 Academic Press, Inc.