A study published in the June issue of the Journals of Gerontology Series A: Biological and Medical Sciences, reports that the most significant difference between identical and fraternal twins who lived into their 70s or 80s was how often they kept in touch by phone or mail.
Identical twins who communicated once a month or more lived longer, on average, than identical twins who did not maintain such frequent contact, and longer than fraternal twins no matter how frequent their communication. The twins analyzed in the study were part of the World War II Veterans Twins Registry - the largest twins registry studied to date - maintained by the National Research Council and the Institute of Medicine, which are part of the country's National Academies.
The difference in median life span between identical and fraternal twins is less than two years - 82 years versus 80.5 years - but the fact that close communication has an effect on the longevity of identical twins indicates there is something special about the relationship between identical twins. Anecdotes are common about identical twins who talk with one another daily, for example, and even twins who "sense" from a distance something affecting their co-twins. Identical twins are monozygotic, that is, they split from the same egg and carry the same genes.
"I think the difference we see is related to the closeness of the relationship between identical twins, which is qualitatively different from the relationship between fraternal twins," said study author Malcolm D. Zaretsky, a UC Berkeley researcher in the Department of Molecular and Cell Biology. "This indicates stronger ties among monozygotic twins, and argues that their genetic relatedness has an environmental influence leading to
Contact: Robert Sanders
University of California - Berkeley