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Twin study of genetic and environmental effects on lipid levels
Author(s) -
O'Connell DL,
Heller RF,
Roberts DCK,
Allen JR,
Knapp JC,
Steele PL,
Silove D.,
Vogler G. P.,
Rao D. C.
Publication year - 1988
Publication title -
genetic epidemiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.301
H-Index - 98
eISSN - 1098-2272
pISSN - 0741-0395
DOI - 10.1002/gepi.1370050504
Subject(s) - heritability , body mass index , cholesterol , twin study , endocrinology , medicine , high density lipoprotein , lipoprotein , monozygotic twin , obesity , dizygotic twin , biology , demography , genetics , sociology
A study of 106 pairs of monozygotic (MZ) and 94 pairs of dizygotic (DZ) twins tested the hypothesis that part of the previously described genetic influence on blood lipid levels can be ascribed to closer similarities among MZ than among DZ twin pairs in environmental factors that affect lipid levels. Participants were adult twin volunteers (age 17–66; 64 male and 136 female pairs) who were selected from the NH & MRC Twin Registry or were respondents to advertisements. They completed a 4‐day weighed food diary from which mean nutrient intake was derived. Information on lifestyle and demographic variables was obtained by questionnaire and a nonfasting blood sample was taken for measures of total, low‐density lipoprotein (LDL) cholesterol, and high‐density lipoprotein (HDL) cholesterol and the HDL 2 and HDL 3 subfractions. Height and weight were measured, and body mass index (BMI) was calculated (kg/m 2 ). Estimates of the heritability of sex‐adjusted lipid levels were 0.72 for total cholesterol, 0.79 for HDL cholesterol, 0.69 for HDL 2 , 0.20 for HDL 3 , 1.06 for LDL cholesterol, and 0.44 for sex‐adjusted BMI. In all cases except for HDL 3 , genetic variance was statistically significant. After adjusting for the effects of environmental variables in three different ways, the estimates of heritability were somewhat lower for total cholesterol, HDL 2 , and BMI, and those for HDL cholesterol (borderline) and LDL cholesterol (definitely) remained statistically significant but were decreased. A genetic influence on HDL 3 was not found. Adjusted heritability estimates obtained from one method of analysis were 0.35 for total cholesterol, 0.49 for HDL, 0.04 for HDL 2 , −0.34 for HDL 3 , 0.66 for LDL, and 0.32 for BMI. These results suggest that the assumptions made in the classical twin study approach are not appropriate when examining genetic effects on lipid levels or BMI, or indeed on any biological variable that may be more similar in MZ twins than in DZ twins. In these circumstances, more complex models may be needed to differentiate between genetic and environmental influences.