What did the researchers investigate?
Researchers at the University of Portsmouth wanted to find out whether regular hot water immersion could improve memory and other thinking skills in healthy older adults.
Their study involved 12 people with an average age of around 69. Participants completed one-hour sessions in water heated to 40°C, two or three times a week for six weeks.
The research received funding from the British and Irish Spa and Hot Tub Association (BISHTA), SPATEX and the Ceperich Educational Trust. It was published in the peer-reviewed journal Experimental Physiology in April 2026.
The sessions took place under laboratory supervision, with researchers monitoring participants’ body temperatures throughout. An hour is longer than the 15-30 minutes commonly suggested for recreational hot tub sessions; BISHTA itself recommends taking a break after 15 minutes for home use.
The study did not compare different session lengths, so we don’t yet know whether a shorter soak at home would offer similar benefits.
What improved?
The researchers tested working memory, reaction time and logical reasoning.
Working memory lets you hold information in mind while using it, such as remembering instructions as you follow them. Two versions of a working-memory test were used, with different levels of difficulty.
A choice reaction-time task tested how quickly participants selected the correct response to a visual cue.
The logical-reasoning task assessed whether participants could judge if a statement correctly described the information shown.
After six weeks, participants performed better on the simpler working-memory test and the logical-reasoning test. The harder working-memory test and the reaction-time task showed no significant improvement with repeated immersion.
What could this mean for everyday thinking?
Remembering instructions, keeping track of information and working through problems help us manage everyday life. That makes these findings worth exploring beyond the question of dementia.
The researchers measured performance directly, rather than relying on participants saying they felt more alert or clear-headed. Whether the better scores would translate into a noticeable difference outside the tests is still unknown.
For example, someone might perform better on a working-memory task without finding it any easier to keep track of what they were doing at home. The study did not assess that kind of everyday change or establish how long any improvement might last after the sessions stopped.
How much can a small study tell us?
The biggest limitation is the lack of a control group. Everyone received the hot water sessions, so there was no comparison with people who took the same tests without following the programme.
People can also get better at tests through practice. Participants were familiarised with the tasks beforehand to reduce this effect, but the researchers acknowledge that learning could still help explain the results.
The harder working-memory test was the study’s primary outcome - the main measure chosen to assess the intervention - and this did not improve significantly with repeated immersion. It is important to consider that result alongside the improvements on the other tasks.
A larger study with a comparison group would help establish whether hot water immersion was responsible for those improvements.
Is there related research into sauna use?
Yes. Long-term Finnish studies have found associations between more frequent traditional sauna bathing and a lower risk of dementia. We explore this in Saunas and Brain Health: Surprising Lessons from a 40-Year Study.
That research followed people’s existing sauna habits and dementia diagnoses over decades. The Portsmouth study instead introduced repeated hot water sessions over six weeks, testing thinking skills during the first and final sessions. One approach examines long-term patterns; the other measures short-term changes in performance.
Neither establishes that hot tubs prevent or treat dementia, and sauna findings cannot simply be transferred to hot tubs. The Portsmouth study did not track dementia diagnoses over time, and its measured blood markers associated with neurodegeneration showed no significant change.
What should hot tub owners take from it?
There is something worth following here: improvements in selected memory and reasoning tasks in healthy older adults. The practical questions are whether other studies find the same results, whether shorter sessions have a similar effect and whether people notice a lasting difference.
For now, the findings give owners no reason to extend their usual soak to an hour. The length of the sessions and the close supervision were part of the experiment.
We’re pleased to see research into the possible benefits of hot tubs. As a retailer, we also owe our customers an accurate account of what it shows. This study is an encouraging start, but it is too early to promise a memory benefit from using a hot tub at home.
