LOOKING GOOD: Lifting weights may be even more beneficial than we thought.

Pumping iron could be a powerful weapon in the fight against dementia, new research suggests.

The University of Sydney study shows resistance weight training could be crucial in keeping the ageing brain nimble, as working out with weights was found to boost the mental agility of older people with mild cognitive impairment - a common precursor of dementia that is not treatable with drugs.

Geriatrician Maria Fiatarone Singh, the study's chief investigator, said weight training stimulated hormones that promoted muscle growth. "It's possible these hormones are also having similar benefits for brain function," Singh said.

One hundred participants did six months of weight training and showed a significant lift in overall cognitive function especially in planning, organising, strategising and visual memory.

The gains were still there a year after the training finished. "The next step is to see how long this lasts and who benefits most from such exercise," Singh said.

Scientists will follow the group for up to five years to see if they can put off or even stop the onset of dementia. Predictions suggest 135 million people worldwide will suffer dementia-related brain diseases by 2050.

"But if a simple cost-effective exercise intervention can show this much promise, I think further research could dramatically reduce that number," Singh said.

The study, published in the Journal of the American Medical Directors Association, compared the effects of weight training, computer-based brain training, and a combination of the two for people over 60 suffering the memory and processing losses linked to mild cognitive impairment.

University of Otago cognitive psychologist Liana Machado said the Australian findings complemented her research into healthy young adults. Even though the studies were different - one focused on weight training, the other on aerobic exercise - Machado said together they pointed to both weight training and aerobic exercise being good for the brain.

"The cognitive benefits gained from regularly engaging in exercise may stem from improvements in brain blood-flow regulation and oxygen availability in the brain," Machado said.

Alongside cognitive impairment, dementia was linked with poor brain blood-flow and oxygen availability. Machado said it was likely all three factors were intertwined.