People who play with their grandchildren stay mentally sharp

The findings are good news for post-menopausal women who are looking for ways to lower the risks of developing Alzheimer's disease, say researchers
The secret to staying mentally sharp later in life is playing with the grandchildren, a study has shown.
The affect was particularly noticeable among grandmothers who cared for their grandchildren.
Researchers said the findings were good news for post-menopausal women, who seek ways to lower the risks of developing Alzheimer's disease and other mental disorders.
However, looking after young children five days a week can take its toll and reduce mental sharpness among older people, the study said.
The Australian study looked at 186 women, aged 57 to 68, who took three different tests of mental sharpness. The vounteers were also quizzed on how demanding their own children had been on them during the past year.
Among the 120 grandmothers, those who spent one day a week taking care of grandchildren performed best on two in three tests.
But those taking care of grandchildren for five or more days a week did significantly worse on one of the tests, which assessed working memory and mental processing speed.
The volunteers were from the Women's Healthy Ageing Project study in Australia and the findings are published in Menopause, the journal of the The North American Menopause Society (NAMS).
Dr Margery Gass, executive director of NAMS, said: "We know that older women who are socially engaged have better cognitive function and a lower risk of developing dementia later, but too much of a good thing just might be bad."
The researchers admitted they were surprised by the finding that looking after grandchildren five or more days a week could be detrimental for mental health.
The report said: "The more time grandmothers spent taking care of grandchildren, the more they felt that their children had been more demanding of them, so maybe mood plays a role in the unexpected result."
The investigators are already following up with more research.
Although other studies have looked at the relationship between mental sharpness and being socially engaged, this is the first time that this type of research has looked at grandmothering.
Dr Gass said: "Because grandmothering is such an important and common social role for post-menopausal women, we need to know more about its effects on their future health. This study is a good start."