What makes a good brain go bad?
This is a question neurologist David Perlmutter, MD, has been trying to answer for decades, as rates of neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and ALS rise rapidly and create a massive public health crisis. More at https://www.mariashriversundaypaper.com/alzheimers-prevention-strategy/
Dr Perlmutter: Neurodegenerative diseases like Alzheimer’s, Parkinson’s, and ALS are on the rise, and for years we thought brain decline was mostly out of our control. But new research is painting a very different picture, and it comes down to a key player: your brain’s immune cells, called microglia. I go deeper on this topic in my new book, Brain Defenders, which is now available for pre-order. More at https://drperlmutter.com/books/brain-defenders/
This book is about empowerment: enabling each reader to become the architect of their brain’s future. Pre-order Brain Defenders today, and take a step toward protecting your brain's future.
BRAIN DEFENDERS read more about microglia at https://drperlmutter.com/books/brain-defenders/
What follows are a series of questions presented to ai and it’s replies:
But first a book review: Great piece on microglia, and I'd love to add one more tool to this conversation: smell testing. The olfactory bulb is one of the very first brain regions damaged by Alzheimer's, even before memory symptoms appear. Our research team as well as researchers at Mass General Brigham and Harvard have been developing a simple, at-home smell identification test that could flag cognitive decline years before traditional symptoms show up. And a Columbia University study found that combining a brief smell test with a short memory exam predicted cognitive decline just as effectively as expensive amyloid PET brain scans.
What I find compelling, both from the literature and from my own experience as a clinician-scientist, is how well this dovetails with Dr. Perlmutter's point that our brain's destiny isn't fixed. If smell testing can catch trouble early, cheaply and non-invasively, that gives us an even wider window to put these lifestyle strategies (exercise, sleep, clean air, real food) to work while they can do the most good.
Based on everything we know today from our lab and others, my moonshot is to see validated smell screening implemented in primary care practices everywhere, right alongside the annual wellness visit or Medicare screening. The science supports it: these tests are low-cost, non-invasive, and can be administered without specialized training. If we can catch neuroinflammatory changes early and pair that detection with the kind of prevention strategies discussed here, we have a real opportunity to change outcomes at the population level.
If you're curious, the University of Pennsylvania Smell Identification Test (UPSIT) is one of the most well-validated instruments out there. It's literally a scratch-and-sniff test. I'd encourage anyone, especially those with a family history of Alzheimer's, to ask their doctor about it. Smell testing is a screening tool, not a diagnostic, and results should always be interpreted by a qualified healthcare provider. Views expressed are my own at: https://www.mariashriversundaypaper.com/alzheimers-prevention-strategy/
- UPSIT (Sensonics International): Considered the gold standard; a 40-item test used for formal olfactory evaluation.
- Sniffin' Sticks (Burghart): Popular odorant pens used by clinicians for screening (12 or 16 item tests).
- B-SIT (Brief Smell Identification Test): A condensed 12-item version used for quick screening.
- Snap & Sniff: A standardized odor identification test kit, often used to test 16 different common odors.
- Process: Users smell a test item (booklet or pen) and choose the correct scent from multiple-choice options.
- Components: Kits usually contain the odorants, instructions, and scoring sheets.
- Usage: Suitable for ages 4–99, taking approximately 8–12 minutes to complete.
THE ABILITY TO SMELL
- Gradual Decline: The sense of smell starts to fade in middle age, with a faster decline after age 60.
- Causes: The decrease is due to both the natural aging process (cell death in the olfactory system) and cumulative environmental damage, such as past infections or toxic exposure.
- Impact on Life: A weakened sense of smell can make food taste bland, impair safety (e.g., failing to smell smoke), and sometimes lead to reduced nutritional intake.
- Related Factors: While natural, this loss can be accelerated by chronic sinus issues, medication side effects, or neurodegenerative disorders like Alzheimer's or Parkinson's.
- Permanent Changes: While temporary smell loss can occur from illness, age-related decline is often permanent
- Significant Association: A 2023 study found that the presence of tinnitus was significantly associated with both subjective smell dysfunction and poor results on formal smell tests.
- Dose-Response Link: The severity of tinnitus appears to correlate with the severity of smell issues. Studies indicated that those with more severe tinnitus had a higher likelihood of significant olfactory dysfunction.
- Shared Underlying Mechanisms: Both conditions are linked to the limbic system in the brain, and both are common in older adults, suggesting a potential shared pathophysiology.
- The coexistence of smell dysfunction and tinnitus, with or without hearing loss, has been reported following the 2020 viral infection.
- Multisensory Environmental Sensitivity: Some researchers suggest that individuals with chronic tinnitus may exhibit a broader "multisensory environmental hypersensitivity," which includes increased sensitivity to smells (chemosensory environmental stressors), even if the physical sense of smell is not severely impaired.
While the exact cause is still under investigation, researchers believe the link may be due to:
- Overlapping Brain Areas: The brain areas that process smell, taste, and hearing partially overlap, and changes in one can affect the others.
- Shared Risk Factors: Conditions that cause hearing loss and tinnitus (like infections, inflammation, or neurological issues) can also affect the olfactory nerves.
- Chronic Stress/Anxiety: Chronic tinnitus often correlates with higher levels of stress and anxiety, which can affect sensory perception, including olfaction.
- Common Dietary Triggers: High sodium (salt) can increase fluid retention and blood pressure, making tinnitus louder. Caffeine, alcohol, and nicotine can dehydrate the body and stimulate the nervous system, exacerbating ringing.
- Neurological Triggers: Foods high in glutamate (MSG, soy sauce, processed foods) can overstimulate nerve cells, while tyramine-rich foods (aged cheese, red wine) can cause blood vessel constriction and dilation, increasing nerve sensitivity.
- Potential Protective Factors: Diets rich in fruits, vegetables, fiber, and dairy may reduce the risk of developing tinnitus. Vitamin B12 and adequate protein intake have also been associated with lower risks.
- Air Pollution (PM2.5, NO2, SO2): Long-term exposure to particulate matter (PM2.5 and PM10) and gases (NO2, SO2) is positively associated with a higher risk of developing tinnitus, with some studies showing a substantial increase in risk in highly polluted areas.
- Ototoxic Chemicals: Substances commonly found in polluted air—such as benzene, toluene, styrene, and xylene—are known to be ototoxic, meaning they can damage the inner ear and the auditory nerve.
- Heavy Metals: Lead, mercury, cadmium, and arsenic, which can be present in industrial exhaust, can accumulate in body tissues and cause both hearing loss and ringing in the ears.
- Impact on Smell: Air pollution can damage the olfactory epithelium and the olfactory bulb in the brain, leading to diminished smell (olfactory dysfunction).
- Tinnitus Diet: Limiting processed foods, excessive salt, caffeine, and artificial sweeteners can help manage symptoms.
- Environmental Protection: Using air filters and wearing masks in heavily polluted areas can reduce exposure to ototoxicants.
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