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Aging is not a passive biological process. We should try to better understand our body and its changes if we want to maintain good health and a strong mind.
By Hannah Keage & Blossom Christa Maree Stephan
The world’s population is aging. The number of adults aged 65 and over is increasing, as is the proportion of the population they represent. However, there is a number of myths associated with what happens to our brain and bodies as we age.
Dementia prevalence increases with age. That is, your chance of having a diagnosis of dementia is greater the older you are. But if you are lucky enough to reach old age, you won’t necessarily have dementia. Dementia is a clinical diagnosis that is characterized by impairments in cognition (the way we think) and functional abilities (that enable us to live independently).
The major type of dementia is Alzheimer’s disease, although there are many other types, such as vascular dementia (caused by vascular changes in the brain, such as strokes), frontotemporal dementia (brain atrophy most pronounced in temporal and frontal cortical regions of the brain), Lewy body dementia (related to a particular protein deposit called a Lewy body), and mixed, in which different types occur at the same time.
However, less than 2 percent of adults aged 65 to 69 have a dementia diagnosis, and this rises to over 30 percent for those aged 90 and over. The flip side of this is that nearly 70 percent of those aged 90 and over don’t have dementia.
Cognition refers to the way we think, but there are lots of types of thinking skills: the speed at which we can respond (processing speed), our ability to remember objects (general memory), our knowledge of words and their meaning (vocabulary knowledge), and many more. These cognitive domains show different patterns of change across adulthood.
It has been estimated that up to 30 percent of dementia cases worldwide are preventable through lifestyle choices.
Processing speed and general memory do appear to decline from after our 20s, which means we are slower at responding to relevant cues and a bit more forgetful as we age. But this is not the case for vocabulary knowledge. On average, we will reach our peak word knowledge in our 60s, and our performance will not markedly decline after that. In fact, multiple studies show that the older you are, the better your performance on the New York Times crossword.
It has been estimated that up to 30 percent of dementia cases worldwide are preventable through lifestyle choices. Evidence shows mid-life heart risk factors, especially diabetes, high blood pressure, obesity, and physical inactivity, increase the risk of developing dementia in late-life, as does having depression, smoking, and low educational attainment.
So, one way to decrease your risk of dementia is to reduce your heart risk factors. For example, exercise more and reduce your weight if you are obese. Engaging with cognitively stimulating activities, such as social meetings and formal (as at university) and informal (as in short courses) education, has been shown to reduce the risk of dementia.
This evidence ties in nicely with recent studies from Europe and the United States that have demonstrated that the individual’s risk of dementia has actually decreased over the past two decades. Why? Well, it appears that older adults are now more physically and cognitively healthy than their predecessors.
Late-life dementia, which is diagnosed when you are 65 years and over, is only influenced slightly by the genetics your parents passed on to you. Nine genes have been identified that either increase or decrease your risk for dementia. There is one that carries some influence: apolipoprotein E. If you have one combination (E4E4 alleles), you are at 15 times more likely to get dementia as someone with the more typical combination (E3E3). However, all other identified genes have only a small effect, with each putting you at a 20 percent increased or decreased risk of developing the disease.
To put these genetic risks in perspective, they are smaller than each of the lifestyle factors mentioned above. That is, dementia is more likely to be caused by obesity (60 percent more likely) or inactivity (80 percent more likely). These comparisons are not perfect, as it may be that genes related to dementia also relate to these lifestyle factors, but it does show how powerful lifestyle factors are.
Simple physics tells us that if the calories we are eating match the energy we are burning, our weight will essentially be stable. Most people believe in this simple and truthful nutritional dogma, but fail to take into account the significant effects of aging on energy metabolism.
As we age, our body composition changes. In particular, we tend to have a reciprocal change in fat (increase) and muscle (decrease), and these changes appear to be different in men and women. Men appear to have a steeper decline in muscle tissue, which accounts for a decline in the total energy expenditure of about 3 percent per decade.
In women, the rate is slightly slower compared to men (about 2 percent per decade). This simply means if you continue to eat and exercise at the same level as you age, you will likely gain weight, and this will mostly consist of body fat.
Aging is not a passive biological process. We need to better understand our body and its changes if we want to maintain health and prevent the onset of diseases such as dementia.
Hannah Keage is a senior lecturer in psychology at the University of South Australia. Blossom Christa Maree Stephan is a senior lecturer at Newcastle University in Australia. This article was originally published on The Conversation.