On the PATH to Good Health
The Benefits of Large Scale Epidemiological Studies
We’re all used to seeing advice on how our lifestyle choices impact on both our mental and physical health, but have you ever stopped to wonder where that information comes from? For example, we often read statistics such as the prevalence of depression or heart disease in 60-70 year olds, or how fish is good for your brain – but how is this information obtained and how do we know if it’s reliable?
Large studies that observe people at one point in time are limited because it is difficult to know whether putative ‘risk factors’ precede a condition or are a consequence of some other social or biological influences. There are also limitations when information is based entirely on questions about past health and medical conditions. Individuals may not be aware they have certain risk factors such as high cholesterol. Even serious medical conditions may go unnoticed. For example, ‘silent strokes’ are small haemorrhages frequently occurring in patients in their 40’s and are usually asymptomatic. At present it’s unknown whether silent strokes may be a precursor to more significant conditions in later life but clearly from a preventative medicine perspective, it would be highly desirable to have this information.
Scientifically, the ideal situation would be to study a large and representative sample of the population from early adulthood to old age recording medical data and correlating this with other lifestyle and well-being factors as they progress through life. In 1999 the National Health and Medical Research Council began funding just such a multifaceted longitudinal study known as PATH - Personality and Total Health. The study is run from the Centre for Mental Health Research at the Australian National University.
The PATH project monitors 7485 volunteers for a whole range of factors such as genetics, cardiovascular health, mental health and cognitive abilities. Subsets of these volunteers are also given regular brain MRI scans to identify things like silent strokes, and brain atrophy, and follow any changes these may lead to in later life.
To cover the entire age spectrum, the participants are drawn from three cohorts whose ages at the beginning of the study were, young (20 -24) midlife (40-44) and older (60-64). The idea being that during the 20 year duration of PATH, and perhaps beyond that in further studies, researchers can follow the course of depression, anxiety, substance use and cognitive ability with increasing age across the adult life span. It will also enable them to pinpoint environmental and genetic risks and protective factors influencing individual differences in the course of these characteristics.
Professor Kaarin Anstey of the ANU Centre for Mental Health Research currently leads the team of investigators working on the PATH project. Her particular area of interest is cognitive and brain ageing. “PATH is the only epidemiological study in Australia that allows us to see the onset of pre clinical dementia in a representative community-based sample. And although we’re only half way through the study we’re already beginning to find some quite interesting outcomes across many aspects of cognition and its relation to lifestyle.”
One of these initial findings was the relationship of alcohol consumption to cognitive ability. When exposed to a series of tasks aimed at measuring the brain’s ability to process and retain information light drinkers (a couple of drinks per day) out performed the abstainers in every age group. “This was really interesting.” Professor Anstey says, “Because it occurs in the young, midlife and old groups. But we shouldn’t jump to conclusions. It doesn’t necessarily mean that light alcohol consumption improves your mental abilities. It could be that genetic or other factors that cause some people to dislike alcohol are also having an effect on cognition. But this is exactly why we need a study like PATH, to generate the breadth and quality of data to eventually enable us to unravel these things properly.”
There weren’t enough heavy drinkers in the survey to draw conclusions statistically significant enough for hard science, but from just looking over the data it would appear that very heavy drinking does significantly reduce cognitive abilities in line with the health warnings most medical professionals issue on alcohol abuse.
“This isn’t a case of everyone should drink,” Professor Anstey cautions, “There are well established links between alcohol and certain cancers and it’s also likely that different people have different reactions to alcohol. But perhaps in the future we may be able to develop a method of reliably setting a safe and appropriate drinking limit on a person by person basis, rather than the current one size fits all approach.”
In many ways large long term medical research projects like PATH are the scientific equivalent to major national infrastructure like roads and railways. They’re expensive and slow to establish but once in place their benefits are so profound it’s hard to imagine life without them!