Researchers at the University College London have investigated the link between emotional and physical well-being and found that happy older show slower declines in physical function as they age.
According to the researchers happy older people are, "less likely to develop impairments in activities of daily living such as dressing or getting in or out of bed, and their walking speed declines at a slower rate than those who enjoy life less".
Dr Andrew Steptoe said: "The study shows that older people who are happier and enjoy life more show slower declines in physical function as they age.
"This is not because the happier people are in better health, or younger, or richer, or have more healthy lifestyles at the outset, since even when we take these factors into account, the relationship persists," he said.
"Our previous work has shown that older people with greater enjoyment of life are more likely to survive over the next eight years. What this study shows is that they also keep up better physical function."
Dr Steptoe added: "Our results provide further evidence that enjoyment of life is relevant to the future disability and mobility of older people.
"Efforts to enhance well-being at older ages may have benefits to society and health care systems."
Facts about the study
The UCL researchers assessed 3,199 men and women aged 60 years or over living in England.
They examined the link between emotional and physical well-being over the space of eight years.
The participants were divided into three age categories: 60-69, 70-79 and 80 years or more - and were asked about their enjoyment of life.
The study was published in the Canadian Medical Association Journal.
Read more on the study
UCL publishes study findings
Read the full paper published in the Canadian Medical Association Journal
Read the Daily Telegraph's coverage of this story: Happiness key to health in old age
Read the Daily Mail's coverage of this story: Cheerful people walk faster and are more active in old age