There are many factors that can lead to dementia, such as age, genetics, and lifestyle choices. The possibility of presenting signs of dementia increases exponentially after 65 years old, but age is known to be a lower risk if all potential comorbid factors are taken out of the equation. Such factors are important to consider. If genes cannot be changed, lifestyle choices are the most reliable? risk factors for dementia as well as the most preventable.
Risk factors of dementia
Early age factors
An early life (age <18 years) factor is associated with less exposure to early life education (e.g., having gone through primary school only).
This means that cognitive and brain resilience in later life is enhanced by building on earlier intellectual stimulation. This also means that through intellectual stimulation, there is a better chance of cognitive and brain resilience in later life through continuous education and other intellectual stimulation. Consequently, people with low levels of education correlate to susceptibility for cognitive deterioration because it results in people having a lower ability to maintain cognitive function. Nonetheless, it is never too late to get started, as indeed it is demonstrated that continuous education is able to increase brain resilience.
Midlife (age 45-65 years) factors
Hypertension
Hypertension and obesity can lead to vascular brain injuries such as microvascular infarcts and macro vascular lesions, which can act as catalysts to develop vascular dementia later in life. People with increase hypertension are known to develop dementia earlier than others.
Obesity
Obesity is associated with an increased risk for cognitive impairment and for developing dementia and Alzheimer's disease. Studies have indicated that the effects of obesity on dementia incidence are enhanced by gaining weight in later life. It is believed that obesity can increase the risk of developing dementia because it leads to a decrease in cerebral blood flow, which results in other microvascular infarcts within the brain. Being overweight or obese, as such, increases your risk of developing dementia.
Furthermore, obesity is related to pre-diabetes and metabolic syndrome which are linked to insulin resistance and increased levels of peripheral insulin, a condition known to impair the clearing of toxins, such as beta-amyloid proteins in the brain (a leading cause to the development of dementia). Higher saturated fat intake, which is associated with obesity, has also been positively associated with higher dementia risk. Factors such as reducing fat, salt (which promotes neurovascular dysfunction) and sugar (which impact obesity) might have, as such, the potential to offset the development, delaying or preventing dementia. Obesity is also linked to the increased possibility of coronary and atherosclerosis diseases and stroke which increase the potential to develop vascular dementia. These metabolic factors are essentially linked with vascular ageing. Vascular ageing is associated with an increased risk of dementia and can be linked to neurodegeneration and brain dysfunction, increasing the risk of dementia.
Studies have provided measures to indicate the potential effect sizes on the association between overweight looking at Body Mass Index (BMI) of individuals (BMI: 25-30), underweight (BMI < 20), or obesity (BMI > 30) and the chance they to develop dementia, indicating a clear risk of developing dementia later in life with an increase following odd ratio BMI 25-30: OR = 1.34, BMI > 30: OR = 1.91 (OR of more than 1.0 indicates an increase in risk (or odds) whereas an OR <1.0 indicates a decrease in risk). In other words, the OR of 1.91 for a BMI > 30 means the individual would have a +- 100 % increase in the odds for developing dementia.
Hearing loss
A person with hearing loss is three times more likely to suffer from dementia. And a preserved hearing is considered to increase the brain's cognitive reserve. Hearing loss is as such, a warning sign of brain function deteriorating. However, this allows you to act on preventing cognitive decline.
These conditions support the theory that "the earlier a cognitive disease is detected, the more therapeutic options are available". Measuring your cognitive abilities early, essentially means having ways to better adapt and act on potential future deterioration. As such prevention of hypertension and obesity and management of hearing loss can contribute to the prevention and the delaying of dementia onset.
Late-life (age > 65 years) factors
Smoking
Smoking is one of the most critical conditions that greatly increase your odds to develop dementia throughout life but its effect is even more statistically significant if you didn't stop smoking late in life. Not only does smoking increase your risk of cardiovascular pathology, and vascular health is essential for preventing dementia, but cigarettes also contain many neurotoxins (e.g., tar) that are harmful to brain health, greatly increasing your risk in developing dementia. Studies indeed have demonstrated that non-smokers (participant that never smoked) had an increased risk to developed any type of dementia (Odds Ration (OR) = 1.30) and Alzheimer's Disease (OR = 1.40) and Vascular Dementia (OR = 1.38) meaning that they had a little less than 50 % more chance to develop such types of dementia.
Frequent and unmoderated alcohol consumption affects cognitive performance and the development of dementia. It is known that frequent consumption of alcohol alters brain functions, reducing blood flow to the frontal areas of the brain and decreases cognitive performance. It is recognised that heavy is a leading cause of brain damage which can lead to alcohol-related dementia or Wernicke-Korsakoff Syndrome. Alcohol is, as such, associated with an increased risk of dementia as it increases oxidative stress in the brain and leads to neuronal vulnerability due to its neurotoxicity properties. And if alcoholism can lead to brain damage, reducing alcohol use may be considered as an effective dementia prevention strategy.
Depression
Depression is a mood disorder that may affect people of all ages but it is usually more prominent in older adults. It is important to note that some forms of depression produce serious neurologic symptoms and are known to accelerate cognitive decline or even dementia. Conducted meta-analysis suggested that depression causes significant alterations in brain structures and functions, and increases the risk for cognitive impairment. As such, although depression can be present in dementia, depression can be a prodromal symptom of dementia, and consequently an independent risk factor for the future prospective development of dementia.
Risk factors that facilitate depression are complex and include the following condition:
- A vulnerability to mood disorders that might be brought up by genetic factors (e.g., serotonin polymorphism).
- An increase difficulty and pragmatical ability of the individual to manage and reduce stress effectively.
- Early-life adversities that have not been integrated into the psyche of the individual.
- Increase and repeated social stress when characterised by unbearing financial strain or and poor social support.
- Extensive engagement in harmful behaviours, lifestyle practices such as hazardous or harmful alcohol or smoking, use of substances known to create dependence, long-term reduction of physical activity and poor dietary habits.
- Other factors that lead to depression are associated with chronic diseases, untreatable sensory or cognitive impairment, and chronic pain.
Physical Inactivity
Physical inactivity is also linked to dementia. Being physically inactive is associated with cognitive impairments, which increase the occurrence of dementia and make you more vulnerable to developing it. Indeed, studies have found that those who engage in physical activity experience improved cognitive function over a period of time and those who did not engage in physical exercise experience a significant decline in their cognitive performance. As such, older adults who exercise more regularly are more likely to maintain cognition than those who do not exercise.
Social isolation
Social isolation is one of the most important factors in the development of dementia. Social isolation increases the risk of cognitive decline and decreases your chances of maintaining brain functions, especially during aging. Social isolation is a global risk factor for dementia because it reduces social engagement, which can lead to decreased life participation and a greater chance of developing mild cognitive impairment and it progressing into dementia as a result of social cognitive inactivity. But social isolation is also known to increase your risks of developing hypertension and coronary heart diseases. As is the case for depression, social isolation is a prodromal condition or integrated with dementia symptoms.
Diabetes
Diabetes and metabolic syndrome are both associated with atherosclerosis and brain infarction which are known causes of neurodegeneration. High concentration of glucose in diabetes mediates mechanisms by which diabetes is known to impair cognition.
In essence, reducing late-life risk factors is associated with improving ways to reducing vascular brain damage and vascular, neurotoxic, and oxidative stress but to an equal extent linked to social and environmental factors, one can easily modify such as having a rich social network, increasing the level of exercising and adhering to a healthy diet.
The Lancet Commission for Dementia Prevention, Intervention and Care indicated the above-mentioned factors as modifiable factors and further indicated the percentage effect they would have in developing dementia if that factor was prevented as an indication of age (see below).
- Diabetes: 70.3 % (Late-life)
- Depression: 58.6 % (Late-life)
- Smoking: 51.1 % (Late-life)
- Social isolation: 45.9 % (Late-life)
- Hearing loss: 23.0 % (Midlife)
- Physical inactivity: 26.6 % (Late-life)
- Education: 19.1 % (Early-life)
- Hypertension: 5.1 % (Midlife)
- Obesity: 2.0 % (Midlife)
Because risk factors for dementia may change with age, analysis of the data allow the evaluation of dementia risk factors that have a higher impact on the function of your age indicating potentially higher risks or not. Reviewing them might increase your chance to prevent dementia by understanding how these risks are modifiable as they are indeed many ways to prevent and/or slow the development of dementia, and which in most case can be prevented by lifestyle modifications and conscious choices to reduce the decline in cognitive function.
Summary
Two things are important to remember. If age is the single greatest risk factor for the development of dementia, several conditions are known to affect people equally regardless of age.
Although the selected modifiable risk factors above are associated with age and were reviewed due to their demonstrated effects on the cognitive decline during ageing, it should be noted however that other factors have equally been considered to hold increase value to estimate the risk of developing dementia. Risk factors such as sleep efficiency, which is essential to clear the accumulation of harmful proteins in the brain (e.g., tau and beta-amyloid proteins), and the extension and level of one's exposure to population (CO2) are gaining prevalence in the overall risk estimation of developing dementia. Finally, certain types of medication are also known to increase the risk associated with developing dementia.
