New research suggests that kids with older dads have more chance of living a long life. But other evidence about delaying fatherhood is mixed.
If you're the wrong side of 30 and nowhere near being ready to reproduce, science has some good news for you. And if you're the offspring of an older dad, it has some good news for you, too.
According to new research from Northwestern University in the US and published this week in the Proceedings of the National Academy of Sciences, older dads may pass on a 'survival advantage' to their children.
The study found that the DNA code of sperm changes as men age, and that this change, when passed on to their offspring, favours longer life.
So is delaying fatherhood a good idea? We take a look at the whole picture.
Older dads make healthier kids?
Put very simply, the new research found that telomeres, which protect the ends of our chromosomes from damage, were longer in young people with older fathers. Telomeres shorten with age until cells can no longer replicate, a key factor in the ageing process.
"As paternal ancestors delay reproduction, longer telomere length will be passed to offspring, which could allow lifespan to be extended as populations survive to reproduce at older ages," said Dr Dan Eisenberg, lead researcher on the study.
In other words, older dads could be bequeathing their children the gift of longer life.
Other advantages of being an older dad
And there are other advantages to being an older dad, according to experts. Maturity, wisdom and financial security are some of the factors that make a happy, focused father and they're more likely to be found in men approaching middle age than their whippersnapper counterparts.
"Older fathers are more likely to have greater control over their careers so are less likely to be focused on proving themselves professionally, and they can be more flexible," says Andrew Watson, author of Down to Earth with a Bump: The Diary of a First-Time Dad.
"When more and more families are dual-career families, this flexibility is of enormous benefit, and can hugely cut down on the stress (and expense) involved with childcare."
Less time in the office means more time with the kids, and what children want more than anything else is time with their parents.
Financial security, though not a given for anyone, is also more likely to be found in older dads. A father who is relaxed about paying the bills and keeping a roof over his family's head is quite simply a more fun dad to have around.
"They (older dads) also have greater life experience and may well have an increased ability to prioritise their children in a way that younger dads might struggle with," adds Watson. "To some extent, they might feel they've had their chance as a single professional, and so are actively looking for a new challenge."
That new challenge is often being the best father they can be not always a priority for 20-somethings desperately trying to climb the greasy corporate pole and keep at least some semblance of a social life together.
The downsides of delaying fatherhood
But there are downsides to delaying fatherhood too, as even the authors of the new research admit. Experts say that there may be advantages in passing on longer telomeres to children, but the advantages may be offset by the fact that middle-aged men tend to display more DNA damage and mutations in sperm.
It's also now known that male fertility tends to decline with age, just as female fertility does. Men who delay fatherhood too long may find they have difficulty conceiving at all. Studies have found that women whose partners were over 35 had more miscarriages than women with younger partners.
So the medical case for delaying trying for children is not clear-cut. And nor are other factors.
"There's no doubt that fatherhood is exhausting, and older dads will feel this all the more," says Andrew Watson. "And while a gap between parent and child in terms of their interests and outlook is perhaps only healthy, that gap is likely to be all the greater and perhaps all the more difficult to handle when the father is much older."
Much older fathers are perhaps less likely to understand the preoccupations of their teenage children, and to empathise with them.
And then there's the simple biological fact that the older you are when you conceive a child, the less time you'll have to be in your child's life. You may pass on age-defying telomeres to your kids, but your own aging process will continue apace.
"There's also the issue that, while it might be well and good for the dad to delay, he needs a partner to have a baby, and there are considerable proven disadvantages of women waiting too late to have a family," says Watson. "So unless we're going to encourage an ever-growing age differential between parents...!"
If your partner is older, the same age or not much younger than you, delaying starting a family could lead to the crushing disappointment of not being able to start a family at all.
Should men delay fatherhood?
So should men put off fatherhood until their jobs are secure, their youthful indulgences are over with, and their sperm sport long and life-extending telomeres to pass on to their children?
It may depend on your personal opinion on what you think is best for your kids, be that a dad with youthful zip and zest or one with the wisdom of maturity.
One thing does seem clear, however. Don't let the new research sway you one way or the other. There are advantages to having a child at 25 and advantages to leaving it another decade, but the most important factor when you and your partner feel ready is something only you can know.