Older people at risk of dementia who follow advice on healthy eating, exercise and brain-training can slow down cognitive decline, particularly in their ability to organize and regulate thought processes, researchers said on Thursday.

In the first randomized controlled trial of its kind, the scientists found that two years of intensive guidance for people aged 60 to 77 led to some striking differences in the brain's capabilities in so-called executive function and processing.

While previous research has shown links between cognitive decline and factors such as diet, heart health and fitness, this trial was the first using a gold-standard design of a "control" group versus a "treatment" group to show that addressing those risk factors might slow or prevent deterioration.

Cognitive decline can be a precursor to dementia, a brain wasting disease that is becoming ever more prevalent as populations age.

Cases of Alzheimer's, the most common form, and other types of dementia are expected to triple to around 135 million worldwide by 2050, according to the campaign group Alzheimer's Disease International.

To see whether health guidance might slow cognitive decline, researchers from Sweden's Karolinska Institute and from Finland's National Institute for Health and Welfare and University of Eastern Finland recruited 1,260 60 to 77 year-olds and randomly allocated half to an intensive guidance group and half to a control group given only routine health advice.

The study was published in the Lancet medical journal.

The intensive advice consisted of regular meetings over two years with doctors other health professionals who gave comprehensive advice on eating healthily, taking exercise engaging in brain training and having regular tests to check blood pressure and other risk factors.

After two years, participants' mental functions were scored using a standard test, the Neuropsychological Test Battery.

Overall scores in the intervention group were 25 percent higher than in the control group, and for some elements of the test, such as executive functioning and processing speed, they were dramatically higher, at 83 percent and 150 percent respectively.

Miia Kivipelto, a Karolinska institute professor who co-led the study, said it showed how "an intensive program aimed at addressing these risk factors might be able to prevent cognitive decline in elderly people who are at risk of dementia."

The study participants will now be followed for at least seven years to see whether the diminished cognitive decline in the guidance group translates into fewer cases of dementia and Alzheimer's.