Have you ever spent the day in a city with such bad air pollution that when you blew your nose the mucus had a black tinge? Have you ever coughed as you breathed in diesel fumes from a passing bus and thought to yourself, “Well, that’s a year gone from my life”? Could it actually be true — that air pollution leads to an early death? The answer, in fact, is an unqualified yes.
Air pollution causes heart disease, lung disease, and early death
It has been known for some time that air pollution causes lung cancer, chronic obstructive pulmonary disease, emphysema, asthma, heart disease, and stroke. One recent study in China estimated that for those ages 75 and older, there are 1,166 early deaths for every 100,000 people — that’s more than 1%. But if it doesn’t kill you outright, can air pollution impair your memory, and cause dementia in general and Alzheimer’s disease (one cause of dementia) in particular?
Studies from several countries link air pollution to cognitive impairment
Three studies from three different parts of the world suggest that air pollution might cause cognitive impairment, dementia, and Alzheimer’s disease. In the first study, researchers from China and the US teamed up to analyze data from China. They found that long-term exposure to air pollution is related to poor performance on both verbal and math tests. Moreover, the poor performance on the verbal tests was more pronounced for older individuals, especially for men and those less educated.
In the second study, researchers in England studied 130,978 adults ages 50 to 79 from 75 medical practices in greater London. They found that from 2005 to 2013, 2,181 older adults from this sample were diagnosed with dementia: 39% with Alzheimer’s disease, 29% with vascular dementia, and 32% without a specific dementia diagnosis. Adults living with the highest annual concentration of air pollution had the highest risk of dementia — 1.4 times the risk of those with the lowest annual concentration. They also found that these associations were more consistent for those given an Alzheimer’s disease diagnosis.
In the third study, published earlier this year, researchers from the United States, including the University of Southern California and Harvard Medical School, studied data from 998 women ages 73 to 87 who had both cognitive tests and MRI scans. They found that those women who were exposed to higher concentrations of air pollution in the preceding three years showed two differences compared to those who were exposed to less air pollution. Cognitively, those exposed to more air pollution showed greater declines in learning a list of words. Anatomically, they showed more atrophy (shrinkage) in those areas of the brain that typically shrink due to Alzheimer’s disease.
Importantly, in all three studies, the researchers controlled for every possible other factor that they thought might make a difference. For example, in this third study they controlled for: sociodemographic factors (age, geographic