Age-related dementia
The biggest cause of memory decline is aging. When most people reach the age of uncertainty, they may not be able to remember things from the past or remember the names of people or things right away. At first, you don't think it's a big deal, but when the same thing happens repeatedly, you start to think about whether you have dementia. This situation is known as the 'senior moment' in the West.
However, this 'forgetfulness' continues to deteriorate in some people and progresses to dementia, while in others it remains as they grow older. The problem is that there is no easy and definitive way to distinguish between "high-risk dementia" progressing to dementia and "successful aging" that progresses from simple forgetfulness to memory retention.
The most common causative disease that causes dementia is Alzheimer's disease, which we are familiar with. It has been called a modern incurable disease because no breakthrough treatment has yet been developed, but little by little, the possibility of a cure is emerging.
Unlike genetic risks, which we can't control, environmental risk factors can be reduced by our efforts. However, from metal ions and toxins dissolved in drinking water, to pesticides in food, to the polluted air we breathe every day, the environment around us is full of substances that can harm our health.
We will focus on how environmental pollution plays an important role in the development of dementia, which is more feared than 'cancer' for us living in the modern age, and in particular, the danger of ultrafine dust, which is getting worse day by day.
Children and the elderly are the most vulnerable to fine dust and air pollution. PM2.5 has been shown to reduce IQ, increase the risk of attention deficit hyperactivity disorder (ADHD) and autism, and reduce the volume of white matter in the left side of the brain in children aged 3 to 9 years. In addition, children born to mothers who are repeatedly exposed to ultrafine dust during pregnancy will have developmental disabilities and incomplete cognitive development.
In a study of children who lived in the air-polluted northern city of Mexico City for more than three years, they performed poorly on psychomotor stability, motor coordination, and resonse time tests. It is speculated that this phenomenon is due to the decrease in a substance called brain-derived neurotrophic factor (BDNF)* due to the inhalation of ultrafine particulate matter.
Adults exposed to polluted air for long periods of time have also been shown to experience accelerated cognitive decline. Chronic exposure to PM2.5 in adults increases the risk of developing all dementia diseases, including Alzheimer's disease. As a result of a study of seniors aged 65 and older living in areas with high air pollution in China and Mexico, the scores of the Simplified Mental State Test (MMSE), a representative dementia screening tool, were significantly lower than those living in places with relatively good air quality.
Among them, the concentration of black carbon and PM2.5, which are the components of diesel engine soot, were significantly correlated with the MMSE score. Another study showed that for every 10 ug/mm3 increase in the concentration of black carbon, cognitive ability declined for two years.
A study from Ontario, Canada, published in The Lancet in 2017, is even more interesting
.It is easy to imagine that the distance a residence is from major highways has a bearing on the level of air pollution. The research team led by Dr. Chen investigated the incidence of degenerative brain diseases in people who lived within 50 meters of arterial roads, 50~100 meters, 100~200 meters, 200~300 meters, and 300 meters or more for more than 5 years.
The conclusion was that the farther away you lived from arterial roads, the lower your risk of developing dementia. There was no significant difference in the incidence of Parkinson's disease or multiple sclerosis, which the team examined together.
Earlier, I talked about APOE 4, a genetic risk factor for Alzheimer's disease. People with this genetic predisposition are more susceptible to air pollution. Even when exposed to the same concentration of air pollution, people with the APOE 4 gene may experience a more severe inflammatory response than those without it, which can lead to more cognitive decline.
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