Age is not just a number, it turns out.

Failed celebrity couples — from Mariah Carey and Nick Cannon to Ashton Kutcher and Demi Moore — are proof of a recent study, which found that marriages with large age gaps are satisfying at first, but the spark fades over time.

The study, published in the Journal of Population Economics, looked at 13 years of Australian marriage data and found that men were, unsurprisingly, happier with a much-younger spouse.

But their satisfaction levels drop over time, according to the researchers from the University of Colorado Boulder.

And, unfortunately for 39-year-old French President Minister Emmanuel Macron and his 64-year-old wife Brigitte, men who married older spouses were the least satisfied of all the couples studied.

Their love died down over time, too, researchers found.

The gap seems to exacerbate one of marriage’s biggest hurdles: financial troubles, says Terra McKinnish, a professor of economics at CU Boulder and a co-author of the study.

“We find that when couples have a large age difference, that they tend to have a much larger decline in marital satisfaction when faced with an economic shock than couples that have a very small age difference,” she says in a statement.

Those who married people closer to their own ages had the most overall satisfaction over time, researchers found, making 33-year-old Mila Kunis a scientifically better fit for 39-year-old Ashton Kutcher than his previous wife, who was 15 years his senior.

Perhaps the findings are something Leonardo DiCaprio, 42, knew all along.

The perma-bachelor, who famously dates young hot things but never marries them, must have had early access to the researchers’ findings.

Or something.