Epidemiology in Military and Veteran Populations Proceedings of the Second Biennial Conference, March 7, 1990 (1991) / Chapter Skim
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Substance Use in World War II Veteran Twins: A Genetic Analysis
Substance Use in World War II Veteran Twins: A Genetic Analysis
Pages 19-34
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From page 19... ...
twin pairs, extended family studies, and adoption-based studies. Hughes recently summarized a number of twin studies in which heritability estimates (the proportion of variance attributed to genetic factors)
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and during middle age; and, third, repeated information on an array of cardiovascular disease risk factors and health behaviors was collected on these subjects when they were 42 to 55 years old and repeated 10 years later by the administration of standardized epidemiological questionnaires. It is our intent in this report to present some preliminary results from a genetic analysis of smoking, alcohol use, and coffee consumption in the NAS-NRC Twin Registry.
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It should also be noted that the NAS-NRC Registry consists of individuals drinking alcohol at levels equivalent to those found in the Finnish Registry and, with regard to coffee drinking, at levels somewhat lower than those of the twins from Finland. SUBSTANCE USE ENVIRONMENTAL CORRELATES AND CO-OCCURENCE The computation of heritability estimates of appetitive behaviors, based on twin studies, is complicated by the fact that multiple nongenetic sources of variance underlie twin similarity or dissimilarity.
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To our knowledge, this approach is new and has been reported only recently in a series of studies of the NHLBI Twin Study subsample.23~24 STATISTICAL METHODS Analyses were directed at estimating the heritable components of smoking, alcohol use, and coffee consumption, both before and after taking into account the effects of other substance use, age, socioeconomic status, and a measure of occupational adjustment. Unadjusted and adjusted heritability estimates were calculated and compared to evaluate the
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Using this approach, individual differences in the joint behavior of smoking, alcohol use, and coffee consumption were reflected in the heritability estimates of the adjusted variables. Smoking status was based on the self-reported number of cigarettes ever smoked per day., ascertaining only current cigarette smoking consumption, as has been done in several earlier studies, is unsatisfactory in intrapair comparisons if the smoking durations are different within the pairs.
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, and C refers to the effect of shared environment. It should be emphasized that the simplest classical twin design assumptions are made in these models: purely additive genetic effects, random mating, the absence of gene-environment correlations or interactions, and the same degree of environmental similarity for MZ and DZ pairs.
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DISCUSSION In this analysis we have demonstrated an epidemiological approach to the investigation of twin similarity in smoking, alcohol use, and coffee consumption. Our approach takes into account confounding and shared covariance between appetitive behaviors, as well as selected demographic variables and their differential impact on MZ and DZ similarity.
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The apparent robustness of the genetic component in smoking, alcohol use, and coffee consumption, even after the adjustment for covariates, supports the general conclusion that each of the substance use behaviors is, in part, genetically determined. Genetic analyses of cardiovascular risk factors have shown a similar robustness under conditions of adjustment for environmental covariates for HDL and LDL cholesterol, triglycerides, relative weight, and some measures of Type A behavioral but not for systolic and diastolic blood pressure.27 Our results also suggest that the most important source of nongenetic variation for each of the appetitive behaviors in late adulthood is nonshared environmental effects.
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Most important, it is, at this point, equally plausible to suggest that differences in smoking, alcohol use, or coffee consumption behavior cause or result from twin similarity or dissimilarity on the variables used in this analysis. Several aspects of the data also limit inferences regarding the differential impact of contact between the twins on twin similarities of appetitive behaviors.
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Smoking and alcohol consumption in adult male twins: Genetic heritability and shared environmental influences. Journal of Substance Use, 2:39-50, 19g0.
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Testing structural equation models for twin data using LISREL. Behavior Genetics, 19:9 35, 1989.
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360 USA 0.52 0.60 a Proportion of total variance attributed to additive genetic effects. Note: Adapted from Hughes., TABLE 2 SUBSTANCE USE IN THE NAS-NRC AND FINNISH TWIN REGISTRIES NAS-NRC Finnish Substance Use Registry Registry Smoking Nonsmoker 19.1 % 38.1 % Current smoker 58.7 42.5 Former smoker 22.2 19.4 Alcohol use (g/month)
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(3) TABLE 4 CORRELATIONS AMONG APPETITIVE BEHAVIORS AND SOCIODEMOGRAPHIC VARIABLES Smoking Coffee Occupational Socioeconomic Age Adjustment Status Alcohol 0.224 (0.021 )
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34 MILITARY AND VETERAN EPIDEMIOLOGY TABLE 5 GENETIC ANALYSES OF CIGAREtl lE; SMOKING, ALCOHOL USE, AND COSINE CONSUMPTION WIN AD WITHOUT ADJUSTMENT FOR COVARIATES Intraclass Genetic Individual Shared Correlations Variance Environment Environment Substance Use MZ DZ H E C ~ ~ . Smoking Log (cig)
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