I have noticed a significant increase in patients with dementia from known high-pollution areas. My patients bear out all that studies have shown till now. There’s now a growing body of evidence linking long-term exposure to air pollution with an increased risk of developing dementia and Alzheimer’s disease.What pollution studies have shown so far?Older adults living in areas with higher levels of air pollution often perform worse on cognitive tests compared to those in cleaner areas. Fine particulate matter like PM2.5 and nitrogen oxides have shown a strong association with negative brain health outcomes. Exposure can lead to accelerated cognitive decline, with studies finding that a higher concentration of certain pollutants is linked to worse performance in areas like verbal learning and memory.The link between polluted air and dementia, stroke and cognitive decline is no longer just a side effect of pollution that we can ignore; it is now a reality.How air pollution impacts brain healthTiny particles, particularly fine particulate matter (PM2.5), can penetrate deep into our lungs and then seep into the bloodstream. Some of these particles are so tiny they also permeate the blood-brain barrier, the natural filter designed to protect our brain from substances that might harm it. Once in the brain, these pollutants can cause inflammation and oxidative stress, which harm nerve cells and disrupt communication among different brain regions.The nose is another entrance. Pollutants can go straight into the brain through the olfactory nerve, which is recognised as a part of the nose that carries our sense of smell. This can lead to local inflammation in brain regions associated with memory and cognition, resulting over time in changes that are associated with diseases like Alzheimer’s and Parkinson’s.The brain is a fragile organ that absolutely depends on ongoing oxygen and nutrient delivery. When air pollutants make their way to blood vessels, they can lead to diminished blood flow to the brain and deprivation of oxygen and other essential nutrients. These can cause mild declines in memory, attention and decision making over time. People often get symptoms like fatigue, irritability and difficulty concentrating or focussing in polluted cities, but you could also think of these as indicators that the brain system is losing some of its efficiency.Story continues below this adLong-term exposure to dirty air also seems to quicken brain ageing. The constant state of inflammation and stress triggered by pollutants damage nerves and the white matter of the brain. These minute changes can quietly build over years until they reach recognizable cognitive decline or dementia.All age groups are at riskThe neurological effects of air pollution are particularly worrisome, as they can affect all age groups. Children who are exposed to polluted conditions may have delayed cognitive development and academic decline, while older adults may be at greater risk of memory dysfunction and neurodegenerative diseases. Even healthy middle-aged individuals can experience subtle cognitive fatigue and decreased productivity when exposed to pollution for long periods of time.In addition to individual health, this poses a societal problem. Populations residing in high-density polluted urban areas (especially populations who have limited access to healthcare) may be at an increased risk. Air quality has thus become a neurological and social determinant of health.Although it is challenging to completely eliminate environmental effects, there are steps we can take to safeguard ourselves. For example, we could use air purification systems in our homes, avoid exercising outdoors when pollution levels are at their highest, wear N95 masks in the most polluted areas, and supplement our diets with antioxidant-rich foods to help mitigate some of the inflammatory load in the brain. In addition to pollution, addressing blood pressure, diabetes, and stress helps keep the brain resilient to pollution damage.Story continues below this adIn my opinion, clean air should be regarded not only as an environmental right but as a necessity for the human nervous system. Our brains are incredibly sensitive to our air supply. Though the processes may be slow, silent, and invisible, they are real. Protecting brain health begins with environmental health.(Dr Gupta is Director, Neurosurgery & Cyberknife, Artemis Hospital, Gurugram)