Helping others for just a few hours a week could slow memory loss and help ward off dementia, a major new study suggests.

Carrying out simple acts of kindness – from formal volunteering to helping friends or neighbours – may slow cognitive decline by up to 20 per cent, researchers have found.

Scientists at the University of Texas at Austin tracked more than 30,000 Americans aged 51 and over for two decades, testing their memory and thinking skills through regular telephone interviews.

Participants completed three assessments measuring immediate memory, working memory and mental processing speed, with higher combined scores reflecting better brain health.

Researchers then examined two types of helping behaviour: formal volunteering, such as charity or community work, and informal helping, including unpaid support for friends, neighbours or relatives they did not live with.

Those who helped others in either way experienced 15 to 20 per cent slower cognitive decline than those who did not.

The biggest benefit was seen in people who gave just two to four hours a week.

'Everyday acts of support – whether organised or personal – can have lasting impact,' said Dr Sae Hwang Han, Assistant Professor of Human Development and Family Sciences at the university, who led the research.

Helping others can help slow cognitive decline, helping people stave of dementia, study finds

He added: 'What stood out to me was that the cognitive benefits of helping others weren't just short–term boosts.

'But [rather] cumulative over time with sustained engagement and these benefits were evident for both formal volunteering and informal helping.

'Informal helping is sometimes assumed to offer fewer health benefits due to its lack of social recognition.

'It was a pleasant surprise to find that it provides cognitive benefits comparable to formal volunteering.'

The findings build on earlier research led by Professor Han, which showed volunteering could counteract the harmful effects of chronic stress on inflammation – a biological process linked to cognitive decline and dementia.

In that earlier study, the protective effect of volunteering was strongest in people with higher levels of inflammation, suggesting those in poorer health may benefit the most.

As a result, Professor Han said older adults with suboptimal health 'may be the ones to benefit from being provided with opportunities to help'.

The latest study, published in the journal Social Science & Medicine, defined formal volunteering by asking participants whether they had spent time in the previous 12 months doing unpaid work for religious, educational, health–related or charitable organisations.

Informal helping was assessed by asking whether they had spent time helping friends, neighbours or relatives they did not live with – and were not paid to assist.