Blood Sugar Usage - a Clue to Brain Aging
A theory already exists that women have more youthful brains than men, but findings till now have been limited to post-mortem analysis and aren't conclusive. So scientists at Washington University School of Medicine in St Louis decided to focus instead on brain metabolism in living people. Though the brain comprises only two percent of body mass, it accounts for 20 to 25% of total body sugar (glucose) consumption. In childhood, brain development and maturity depend on energy created from even higher levels of glucose. In fact, in childhood and in young adults, the brain's resting glucose metabolism is 12 to 15% more than is required to account for its oxygen consumption rate. This excess glucose utilization is called aerobic glycolysis. During a person’s adult years this process is gradually scaled down, and brain metabolism slows. Less and less energy from glucose is needed for development and maturity. By the time people reach their 60s, aerobic glycolysis has fallen to a tiny amount. Because this loss of aerobic glycolysis is the main driver of metabolic changes seen in the aging brain, the scientists decided to use this as a marker of brain aging in adults.Men's Brains Age Faster
For their study, 205 men and women aged 20 to 82 with normal cognition were recruited and given a series of PET scans to measure the flow of oxygen and glucose. The fraction of glucose committed to aerobic glycolysis in various regions of the brain was established for each participant. The results were fed into a sophisticated machine-learning algorithm that was trained to use the information to find a relationship between the participants’ actual age and brain metabolism, and whether their brains appeared metabolically younger or older than they should be. Lead researcher Dr. Manu Goyal explains, "We used a machine-learning technique to guess at how old each of our study participants was based only on their brain metabolism. We found that the technique guessed quite well, but often predicted a person's age to be more or less than their actual age." The key finding from the analysis was that women's brains were metabolically younger than men's by an average of 3.8 years, and this was the case throughout the entire age span of the participants. Dr. Goyal stated that “the average difference in calculated brain age between men and women is significant and reproducible," but admits he's not certain what the results of the study tell us just yet other than "sex has an effect on how the brain ages, metabolically speaking." He believes greater youthfulness in the brains of women could provide a degree of resilience to aging-related changes, and may be "the reason women don’t experience as much cognitive decline in later years."Striking Results – and a Bit Discouraging
Samuel Neal Lockhart, Assistant Professor of Gerontology and Geriatric Medicine at Wake Forest School of Medicine, was impressed with the research: "This immense amount of data...convincingly show that...males have more accelerated metabolic brain age." The findings, he continued, "not only help us to understand how factors like sex contribute to different trajectories of metabolic brain health in later life, but also help us to understand the potential causes and early signs of Alzheimer's disease." There seem to be some major downsides to being a man - at least as far the brain is concerned. Studies have found older men score worse than women of the same age on tests of reason, memory and problem solving. It's already established that men's brains shrink faster than women's. Now we find their brain metabolism ages faster.