Ten-year follow-up for male twins divided into high- or low-risk groups for ischemic heart disease based on risk factors measured 25 years previously

More favorable midlife cardiovascular risk factor levels in male twins and mortality after 25 years of follow-up is related to longevity of their parents

BACKGROUND

Genetic studies of life span in humans have used broad survival measures, most commonly longevity, which is moderately correlated between parents and offspring. We examined whether genetic cardiovascular disease risk factors in male twin offspring are related to longevity of their parents in the National Heart, Lung, and Blood Institute twin study.

METHODS

Cholesterol levels, body mass index, blood pressures, and pulmonary function measured over the first three examinations (average subject age 48, 58, and 63 years, respectively) were compared with the twins' paternal, maternal, and parental mean longevity divided into upper versus lower quintiles. The presence of an apolipoprotein E epsilon 4 allele typed from DNA collected at Exam 3 and mortality in the twin cohort through 1997 were also examined in relation to parental longevity quintiles.

RESULTS

Twins, particularly whose fathers died at younger ages, had significantly higher total cholesterol (p <.05), ratio of total cholesterol to high-density lipoprotein (p <.01), and blood pressures (p <.01) in middle age. This relationship decreased at the subsequent two examinations, but consistently, twins with longer-lived parents tended to have better risk factor profiles. A twin death (mean age 65) was significantly more common in families with mothers (p <.001) and, to a lesser extent, fathers who died early. An apolipoprotein epsilon 4 allele was more common in families with parents' age at death in the lowest quintile (p <.05).

CONCLUSIONS

Systolic blood pressures, cholesterol levels, and the presence of the apolipoprotein E epsilon 4 allele likely contribute to the observed familial correlations in longevity that have been reported in the literature.

Influences of chorion type on measurements of the corpus callosum in adult monozygotic male twins?

MRI imaging was used to estimate volumes of corpus callosum structure in 45 pairs of identical (monozygotic, MZ) twins from the National Heart, Lung, and Blood Institute (NHLBI) twin study. Age range of the study subjects was from 68-78 years. Finger, palm, and footprint data (dermatoglyphics) collected at previous examinations of the NHLBI twin study were available for 39 pairs. The dermatoglyphics were scored for an index to retrospectively assess chorion type in MZ twin-pairs. The results indicated an association between variability in various structures of the corpus callosum with some of these dermatoglyphic traits, suggesting greater structural variation within pairs with dichorionic placentas. In contrast, total intracranial volume, which has similar heritability estimates as a result of shared genetic effects with the corpus callosum, was unrelated to the dermatoglyphic traits. The results provide indirect evidence that the intrauterine environment may influence twin-pair similarity of corpus callosum measures in adults.