Analysis: recent research suggests middle age could mark a shift in brain ageing with our blood in our 40s more informative about our brain in our 60s
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Imagine if a blood test in our 40s could predict the future health of our brains in our 60s. Imagine if it could predict how well we are likely to remember things, how quickly we will be able to process information or how often we might stumble over words.
Based on recent scientific strides, this may be more than click-bait. It begs the question "how does our blood know about the health of our brain, much less its future health?". Here is the actual (but critically true) click-bait: ageing spreads through the body like an infection.
Research has suggested that we can be older or younger than our chronological age. As Harvard geneticist David Sinclair likes to quip, "the body doesn't care how many times the earth went around the sun". The clock of life doesn't always tick regularly. Unlike our common conception of ageing, the clock may start to tick faster in our 40s and 50s – think of it as "middle-ageing".
From The Economist, what happens to your brain as you age
Over time, the function of the body declines, and this decline manifests in the blood. For instance, immune cells in the blood are on constant patrol not just for pathogens, but also for evidence of things gone awry in our own cells, be it cancerous growth, damaged DNA, or other sources of cellular dysfunction related to ageing (by the way, there's 12 of them).
When it finds the source of disrepair, the immune system does what it does best: it sends out chemical messengers that start the process of inflammation. There is actually a gradual build-up of inflammation in the body as we age, a process called 'inflammageing'. Unfortunately, these inflammatory messengers can spread to the brain and negatively affect its health, especially the area that creates our memories – the hippocampus.
Through blood-born messengers like these, other organs of the body can influence how fast the brain ages, speeding it up or slowing it down. Interestingly, it's around the time of middle age that the contents of blood undergo some of the biggest changes. Some of these changes (involving cells, metabolites, and chemical messengers) are very likely to turn the hands on the brain's clock. Not only can we be biologically younger or older than our chronological age, our organs can have different ages, and age at different rates.
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From RTÉ Radio 1's News At One, a new study finds Covid may have an impact on the brain health of over 50s
For example, the numbers and strength of connections between brain cells seems to reach a maximum during middle age. The way different brain areas communicate and transfer information is optimal in some respects during early midlife. We also become wiser and acquire more knowledge with age (termed "crystallized intelligence").
But where there is a peak, there is a slope. It's during middle age that the brain begins to undergo accelerating change in the very same connections and communication, which can have noticeable effects. Memory for everyday events, in particular, seems to be affected by "middle-ageing". Tests on memory function have revealed that it's during the transition from middle to old age when people begin to diverge the most. Perhaps, then, unhealthy cognitive ageing could be caught early.
For women, midlife also brings the onset of menopause, which is often associated with subjective memory complaints. This may not be a coincidence. Natural fluctuations of sex hormones during the menstrual cycle seem to affect the hippocampus, the seat of memory formation. Remarkably, its size has been found to fluctuate in sync with sex hormones. An earlier onset of menopause is also associated with faster biological ageing.
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From RTÉ Radio 1's Today with Claire Byrne, Dr Harry Barry GP and Dr Ann-Marie Creaven from the University of Limerick on forgetfulness in middle age
However, it's important to stress that there is a lot of variation between people. Some women experience very few cognitive changes, and some changes revert after menopause. This highlights just how complex the midlife period can be. The clock of life doesn’t always tick regularly.
Science has long focused on brain changes during older age, when the effects of time are most pronounced, but by then, it can often be too late to intervene. In contrast, middle age is quickly emerging as a period of life that is prognostic of future health while also allowing for early intervention. This is important because an increasing number of studies are now finding that biological measures of age are more informative about the likely course of future health than chronological age.
Our blood in our 40s is more informative about our brain in our 60s
Yet, as some have pointed out, our societies still base some of its most important decisions (like social security and pension eligibility) on chronological age. Meanwhile, our blood in our 40s is more informative about our brain in our 60s than 60 earthly revolutions around the sun are.
Fortunately, the benefits of good habits, like exercising and a healthy diet can extend to the brain via the blood. There are rejuvenating messenger molecules secreted by the body's organs that have beneficial effects on the brain’s ability to form new connections and new brain cells (neurogenesis). If we could harness such blood-borne molecules, we may ultimately be able slow the ticking of the brain’s clock or even reverse it.
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The views expressed here are those of the author and do not represent or reflect the views of RTÉ
