Grandparents planning hefty amounts of childcare this half-term might want to think again after research claimed to disprove previous findings of a “rejuvenating effect” from looking after grandchildren.

Many studies have appeared to show mental and physical health advantages for those who care for their grandchildren. But none involved researchers talking to the same grandparents before and after their caregiving responsibilities began.

When the authors of Is There a Rejuvenating Effect of (Grand)Childcare? A Longitudinal Study, published this week in The Journals of Gerontology, did that, they found that caring for grandchildren failed to make grandparents feel any younger than their actual age.

The age people feel they are – as opposed to the age on their birth certificate – is seen as a strong indicator of their mental and physical wellbeing, sometimes even outperforming chronological age as a direct predictor of psychological and health-related outcomes, including risk of death.

“This is the first study to look at the same people before and after taking up grandparental childcare in terms of the effects on subjective age,” said Dr Valeria Bordone, co-author of the report.

Bordone is also co-author of a 2016 report, Do Grandchildren Influence How Old You Feel? That found over-65s who take care of grandchildren feel at least two years younger than their age, rising to 2.6 years for men aged 74-85.

But her new findings have given her pause for thought. “Contrary to our 2016 findings, our new study found no youthful effect of the transition from not being a caregiver to becoming a grandchild caregiver for either grandfathers or grandmothers,” she said.

The new study was welcomed by Prof Cecilia Tomassini, a leading member of the Grandparenting in Europe network of researchers.

“This research adds important insight to a question that hasn’t previously been interrogated by going back to the same people,” she said. “Even studies that have gone back to the same group have tended to lose sight of grandparents in ill health because they’ve dropped out of the research. This means those papers have ended up by only looking at healthy grandparents, which is why they’ve been getting, until now, largely positive responses.”

Bordone now believes that attributing a causal effect between childcare provision and feeling younger is wrong. Instead, she said, the link is likely to have more to do with hidden selection effects. “It may well be that personality traits and family values that mean grandparents already have a young, subjective age are overrepresented among individuals who provide care to others,” she said.

In short, rather than childcare making grandparents feel young, it’s the grandparents who feel young already who do more childcare.

When Bordone researched this issue in 2016, she asked adults who care for their grandchildren how young and healthy they felt. This time, she questioned the same 7,730 adults aged 50–85 before they began childcare. Returning over a period of time during which 21% started providing childcare, she asked the same question. Those who never provided childcare remained in the control group.

If your children’s grandparents are now reluctant to step up this half-term, you might have more luck asking a friend or neighbour of grandparent age.

The research threw up the unexpected finding that there are slight benefits in older adults looking after young children who are not their own kin. The hypothesis, said Bordone, is that unrelated children bring with them the rejuvenating effect of youth – without the same reminder of old age that grandchildren do.

“Grandparenthood is a powerful reminder of a person’s ageing and as such it is likely to affect subjective age,” she said.