Name some issues brand new to this world in the last 100 years. How about nuclear war, environmental pollution and climate change? Medically, we can blame carpal tunnel syndrome on the typewriter or computer keyboard, and “automobile knee” on that awful car commute. Hard to know whether these marks on modern society are preferable to being chased by a woolly mammoth ages ago.
Blame it on Dad
In my world of men’s health, there is another “new” problem that is less than a century old: the higher rate of diseases in offspring begot by older fathers. Over the last decade, the evidence is convincing that autism, schizophrenia and bipolar disorder rates are higher in the kids of older dads. By older dads, I mean men who bear children in their 50s or beyond compared to men in their 20s. This is totally separate from the chromosomal issues that older mom’s bring to bear on kids (which by the way is also a relatively “new” issue in the last century. We think that the cause of this is that the fast-spinning, sperm-making machinery wears out as men age. And when it wears out, little things called mutations pop up more often. Since point mutations are small, they are quite good at sneaking passed the usual quality control scans, and so get passed to children.
Why is the issue of offspring health of old dads a relatively new one? Well, because until 100 years ago men never really lived long enough to be older dads (see Figure). Yup, human life expectancy remained about the same, about 30 years from birth to death, from the Neolithic Age through Classic Greece, up through the Middle Ages and into the late 1800s. And 30 years is hardly considered “old” for a dad by today’s standards.
But, maybe older men just aging gracefully without more kids and not necessarily becoming older dads? ‘Fraid not. A recent U.S. Vital Statistics registry reported that the birth rate over the last decade relative to father’s age has increased by between 10-20% for each 5-year interval of men’s ages 35 to 54 years. In England too, the rate of new fathers aged 35 years or older has tripled over the last 3 decades. So, at least in the US and several other developed countries, older men are indeed becoming older dads.
So, now what do we do? Unlike restoring a vintage car, in which parts can be found or made new, this side effect of longevity currently has no cure. We can either have kids earlier like we did in the past, bank sperm when young to have kids when older, or chock the whole thing up to evolution and hope for the best. In the words of Abe Lincoln: “It’s not the years in your life that count. It’s the life in your years.” I would love to hear your thoughts!