Brain training - playing online games that give memory and reasoning skills a workout - is beneficial for older people, a large-scale study has concluded.
Researchers at King's College London found the mental exercises kept minds sharp and helped people with everyday skills such as shopping and cooking.
Nearly 7,000 people aged 50 and over signed up for the six-month experiment, launched by BBC TV's Bang Goes The Theory.
Longer studies are now beginning.
The volunteers were recruited from the general population by a partnership between the BBC, the Alzheimer's Society and the Medical Research Council.
As far as the investigators were aware, none had any problems with memory or cognition when they signed up to the experiment.
Some of the volunteers were encouraged to play online brain training games for 10 minutes at a time, as often as they wished. The others - the control group - were asked to do simple internet searches.
The researchers tested the subjects on a series of medically recognised cognitive tests at baseline and then again at three months and six months to see if there was any detectable difference between the groups.
The researchers found after six months, those who played "brain training" games for reasoning and problem-solving kept their broader cognitive skills better than those who did not.
The benefit appeared to kick in when people played the games at least five times a week.
And people over 60 who played these games reported better scores for carrying out essential everyday tasks, the Journal of Post-acute and Long Term Care Medicine reports.
But an earlier analysis by the same researchers suggests brain training has no benefit in people younger than 50.
The researchers from the Institute of Psychiatry, Psychology & Neuroscience at King's are starting a longer trial to establish whether this approach could help prevent the development of dementia.
Dr Doug Brown of the Alzheimer's Society said: "Online brain training is rapidly growing into a multi-million pound industry and studies like this are vital to help us understand what these games can and cannot do.
"While this study wasn't long enough to test whether the brain training package can prevent cognitive decline or dementia, we're excited to see that it can have a positive impact on how well older people perform essential everyday tasks."