Connections: older parenthood and the environment

Delayed Childbearing in US

Delayed Childbearing: More Women Are Having Their First Child Later in Life, T.J. Mathews, M.S., and Brady E. Hamilton, Ph.D., Aug 2009

How Older Parenthood Will Upend American Society by Judith Shulevitz

Judith Shulevitz’s article in the New Republic on older parenthood discusses how our genes are affected by time and environmental exposures and how those changes can be passed on to children. The focus of genetic counseling has been on mothers considering pregnancy at an older age (over 35). Shulevitz describes the new research that includes a father’s genome:

But the associations between parental age and birth defects were largely speculative until this year, when researchers in Iceland, using radically more powerful ways of looking at genomes, established that men pass on more de novo—that is, non-inherited and spontaneously occurring—genetic mutations to their children as they get older. In the scientists’ study, published in Nature, they concluded that the number of genetic mutations that can be acquired from a father increases by two every year of his life, and doubles every 16, so that a 36-year-old man is twice as likely as a 20-year-old to bequeath de novo mutations to his children.

The Nature study ended by saying that the greater number of older dads could help to explain the 78 percent rise in autism cases over the past decade. Researchers have suspected links between autism and parental age for years. One much-cited study from 2006 argued that the risk of bearing an autistic child jumps from six in 10,000 before a man reaches 30 to 32 in 10,000 when he’s 40—a more than fivefold increase. When he reaches 50, it goes up to 52 in 10,000.

She goes on to discuss how epigenetics, or the study of how environmental exposures can cause genetic mutations that are passed down to future generations:

To the danger of age-related genetic mutations, geneticists are starting to add the danger of age-related epigenetic mutations—that is, changes in the way genes in sperm express themselves. Epigenetics, a newish branch of genetics, studies how molecules latch onto genes or unhitch from them, directing many of the body’s crucial activities. The single most important process orchestrated by epigenetic notations is the stupendously complex unfurling of the fetus. This extra-genetic music is written, in part, by life itself. Epigenetically influenced traits, such as mental functioning and body size, are affected by the food we eat, the cigarettes we smoke, the toxins we ingest—and, of course, our age. Sociologists have devoted many man-hours to demonstrating that older parents are richer, smarter, and more loving, on the whole, than younger ones. And yet the tragic irony of epigenetics is that the same wised-up, more mature parents have had longer to absorb air-borne pollution, endocrine disruptors, pesticides, and herbicides. They may have endured more stress, be it from poverty or overwork or lack of social status. All those assaults on the cells that make sperm DNA can add epimutations to regular mutations.

Read on for her thought provoking discussion that touches on policy, women’s and human rights, and procreation: http://www.tnr.com/article/politics/magazine/110861/how-older-parenthood-will-upend-american-society?page=0,0.

2 responses

  1. Intriguing and sobering. I did a little reading on epigenetics while pregnant with my daughter (who turned 1 a couple weeks before I turned 36, by the way, and whose father is 42, so I guess we are in this category of older parents “upending” society). The somber fact that genetic mutations from the way we’ve lived and the choices we’ve made pass on from generation to generation makes sense as I recall how someone told me that I should eat well in pregnancy because my daughter’s eggs held my future grandchildren! I appreciate the newer research on the father’s genome, after all the focus on mothers, and the interesting hypothesis that the higher rate of autism may be explained by the increasing numbers of older dads who’ve been exposed to more environmental toxins. Although there’s no turning back the clock now, I’m glad we are starting to iron out the science of all of this so we can educate the next generation about limiting environmental toxins, should our daughters and sons end up parents after 35, to the extent that they have control over these factors.

  2. Nicely said!