GENETIC AND ENVIRONMENTAL-INFLUENCES ON PULMONARY-FUNCTION IN AGING SWEDISH TWINS

Background. In addition to their value in assessing pulmonary health a nd disease, spirometric variables have been shown to be powerful predi ctors of time until death in aging populations. The sources of variabi lity in these spirometric values are consequently of relevance to basi c gerontological research, and also of potential value in clinical app lication. The objective of this study was to estimate genetic and envi ronmental sources of variance in pulmonary function. Methods. The stud y involved 230 Swedish twin pairs (mean age = 64.9 years), of which nu mber 37 monozygotic (MZ) pairs and 72 dizygotic (DZ) pairs had been se parated and reared apart. Comparing these groups to the 57 MZ and 64 D Z pairs reared together permits stronger interpretation than that of c onventional twin studies. Measures of vital capacity (VC) and forced e xpiratory volume in one second (FEV,) were residualized for height, ag e, sex, and tobacco consumption in pack-years. Results. Maximum likeli hood analyses of VC and FEV, gave heritability estimates of .48 and .6 7, respectively. Age effects were explored both by dividing the sample into two cohorts, respectively above and below 65 years, and by movin g interval analysis. In the two-cohort analysis, heritabilities were s omewhat higher for the older cohort than the younger cohort for FEV,. The opposite was true for VC: heritability was lower in the older coho rt, and there was evidence for a shared rearing environmental effect f or this group. Moving interval analysis suggests these differences are gradual rather than saltatory. There were no gender differences in pa rameter estimates. Conclusion. Genetic factors account for between one -half and two-thirds of the variability in pulmonary function. There i s a suggestion of age differences in the relative importance of geneti c and environmental influences.