Life expectancy of monozygotic and dizygotic twins

White male twins from the NAS-NRC twin sample, who were born in the U.S. between 1917 and 1927 and served in the military, are used to estimate variability in hazard functions for those twins who died during the period 1974-1990. Roughly the same number of MZ and DZ twins died during this period, but their death rates are similar. DZ twins exhibit greater within-pair variation. Using hazard and other analyses, the only statistically significant variables are found to be being a DZ twin (in level equations), date of birth, and, sometimes, wife's religious preference. Variables not significant for level or within-pair equations, include own religion, parental education, working overtime frequently, and number of children. The greater variation in life expectancy of DZ twins is hardly surprising and may say something about the lack of comparability in phenotype variance of DZ twins, which in turn may be worrying.