Long hours spent caring may speed cognitive decline in middle-aged and older people, new research suggests.
Researchers found that providing care for 50 hours or more a week was linked to faster decline in memory and thinking skills.
However, lighter caring duties of five to nine hours a week appeared to support brain health, with benefits lasting into older age.
Carers UK called the findings “extremely worrying” and said they highlight how long hours spent providing care raise the risk of social isolation and burnout.
Dr Baowen Xue, an academic at University College London and lead author of the paper, said: “Our study shows that the caring responsibilities many people take on in later life can be a double-edged sword.
“On the one hand, lighter caring responsibilities can be good for you by providing mental stimulation from interacting with loved ones or others you’re helping and a sense of purpose and usefulness.
“But being overloaded with caring tasks has exactly the opposite effect and can accelerate people’s mental decline in terms of not being as mentally sharp or quick-thinking as they used to be.”
Researchers compared the cognitive health of 2,765 carers aged 50 and over with 2,765 non-carers of the same age who were part of the English Longitudinal Study on Ageing.
Participants were 60 years old on average, and women made up 56 per cent of the group.
Researchers looked at executive function and memory. Executive function means the mental skills used for planning, decision-making and handling competing tasks.
The paper said manageable levels of care may provide mental stimulation and help maintain executive function in later life.
It also found that providing a few hours of support outside the household may help carers maintain cognitive health as they age.
However, carers providing 50 or more hours of care a week showed accelerated cognitive decline.
The researchers suggested the demands of high-intensity care may outweigh any mental stimulation gained from caring.
People providing this level of care are often full-time carers, leaving limited time for work, social life, sleep and rest.
The paper said the intensity of care may lead to loneliness and disrupt sleep, further compounding negative effects on cognition.
The UK’s 2021 census found that 5.8m people provide unpaid care, with 1.7m doing so for at least 50 hours a week.
Research from Carers UK last year found just over half of carers had increased the amount of time they spend caring.
The charity also reported that 74 per cent of carers feel stressed or anxious, 40 per cent feel depressed and 35 per cent say their mental health is bad or very bad.
Helen Walker, chief executive of Carers UK, said: “These findings are extremely worrying, showing that many hours of caring could contribute to cognitive decline.”
She said the government, local councils and the NHS needed to provide more support for family carers.
Research by the Joseph Rowntree Foundation for the IPPR thinktank last year found that the proportion of adults providing care for more than 35 hours a week rose by 71 per cent between 2003-04 and 2023-24.
The study also found that caring for someone within the same household was linked to a faster decline in cognitive function than caring for someone outside the home.
The researchers called for more support for intensive carers, including better access to funded formal care and replacement care.
They said: “By 2040, around 20 per cent of adults in England will be living with major illnesses.
“With the NHS struggling to cope and social care in crisis, much of this growing demand for care will fall on family members and friends who step in as unpaid carers.
“Our findings show that this shift has profound implications: carers’ wellbeing is often overlooked and there is a real danger that many people overburdened with caring responsibilities will suffer the consequences.”
Caroline Abrahams, charity director at Age UK, said: “Anyone who cares intensively is likely to struggle to fit in the time for enough rest, sleep and time away doing things they enjoy.
“These are essential human needs which, when met, set you up for good mental and physical health.
“In most cases people care because they want to and because they are deeply committed to someone they love. Caring in and of itself is not the problem here.
“But we need to do a lot more to support people in this position so they can continue to stay fit and well, and so they have the time and space to enjoy living their own lives, while helping someone else to live theirs.”