Longevity Not Very Heritable
James W. Vaupel says that how tall your parents are compared to the average height explains 80 to 90% of how tall you are compared to the average person. But “only 3% of how long you live compared to the average person can be explained by how long your parents lived. … Even twins, identical twins, die at different times.” On average more than 10 years apart.
Dr. Kaare Christensen studied twins. The idea was to compare identical twins, who share all their genes, with fraternal twins, who share some of them. He took advantage of detailed registries that included all the twins in Denmark, Finland and Switzerland born from 1870 to 1910. That study followed the twins until 2004 to 2005, when nearly all had died.
They restricted themselves to twins of the same sex, which obviated the problem that women tend to live longer than men. That left them with 10,251 pairs of same-sex twins, identical or fraternal.
The genetic influence was much smaller than most scientists had assumed. The vast majorities of identical twins die years apart.
There was almost no genetic influence on age of death before 60. The studies of twins found almost no genetic influence on age of death, except among people who live to be very old.
A woman whose sister lived to be 100 has a 4% chance of living that long. That is better than the 1% chance for women in general, but still not very great because the absolute numbers are so small.
A man whose sister lived to be 100 has just a 0.4% chance of living that long. Men in general have a 0.1% chance of reaching 100.
Dr. Paul Lichtenstein analyzed cancer rates in 44,788 pairs of Nordic twins, and found that only a few cancers — breast, prostate and colorectal — had a noticeable genetic component. If one identical twin got one of those cancers, the chance that the other twin would get it was generally less than 15%, about five times the risk for the average person but not a very big risk over all.
Parkinson’s has no detectable heritable component, studies repeatedly find. Heart disease appears to be indiscriminate, striking almost everyone eventually.
Chronic diseases strike almost at random among the elderly.
Matt McGue contrasts life spans with personality, which, he says, is about 50% heritable, or attention-deficit hyperactivity disorder, which is 70 to 80% heritable, or body weight, which is 70% heritable.
Researchers have isolated a gene for a cholesterol-carrying protein that affects risk for heart disease as well as Alzheimer’s disease. Those who have that gene have double the chances of living to 100. (Only about 2% of people born in 1910 could expect to reach 100.)
Dr. Christensen found that birth order made no difference in health or longevity.
“Live Long? Die Young? Answer Isn’t Just in Genes,” by Gina Kolata