Melbourne: Regular exercise of any type, from walking the dog to mountain climbing, during middle ages is the best lifestyle change a person can make to prevent cognitive decline in later years, a landmark 20-year study has found.
Recent research shows abnormalities in brain tissue begin several decades before the onset of cognitive decline, but little is known about the lifestyle factors that might slow the onset of decline in middle age. As the incidence of Alzheimer's disease diagnosis doubles every five years after 65, most longitudinal studies recruit participants over the age of 60 or 70.
The new study by University of Melbourne tracked 387 Australian women for two decades. The women were aged 45-55 when the study began in 1992. Researchers wanted to find out how lifestyle and biomedical factors - such as weight, BMI and blood pressure - impacted memory 20 years down the track.
"There are few research studies which have data on participants from midlife and have assessed cognition in all their participants in later life," said Cassandra Szoeke, from the University of Melbourne, who led the study.
"This research is really important because we suspect half the cases of dementia worldwide are most likely due to some type of modifiable risk factor," said Szoeke. "Unlike muscle and vessels, which have the capacity to remodel and reverse atrophy and damage, neuronal cells are not nearly so versatile with damage and cell loss is irreversible," she said.
Over two decades, researchers took a wide range of measurements from the study participants. They made note of their lifestyle factors - including exercise and diet, education, marital and employment status, number of children, physical activity and smoking. They also measured hormone levels, cholesterol, height, weight, body mass index (BMI) and blood pressure at 11 points throughout the study. Hormone replacement therapy was factored in.
The women were given a Verbal Episodic Memory test in which they were asked to learn a list of 10 unrelated words and attempt to recall them 30 minutes later.
When measuring the amount of memory loss over 20 years, frequent physical activity, normal blood pressure and high good cholesterol were all strongly associated with better recall.
Once dementia occurs, it is a slow moving freight train to permanent memory loss, Szoeke said. "In our study more weekly exercise was associated with
better memory. We now know that brain changes associated with dementia take 20 to 30 years to develop," she said. "The evolution of cognitive decline is slow and steady, so we needed to study people over a long time period. We used a
verbal memory test because that's one of the first things to decline when you develop Alzheimer's disease," Szoeke said. The study was published in the American Journal of Geriatric Psychiatry.
