Loss of Smell May Be an Early Sign of Brain Diseases

Scientists have learned smell loss can be a diagnostic tool for Parkinson’s and Alzheimer’s. Plus: the week’s top science news; requiem for a foghorn; and more. [View in browser]( | [Join Nautilus]( July 18, 2023   Did a friend forward this? [Register here](. This Tuesday, your FREE member newsletter includes the week’s top science news—plus one full story, below, from The Porthole, our section for short sharp looks at science. Enjoy!   DISCOVERIES The Top Science News This Week   [Supermassive Dark Star Candidates Seen by JWST]( Hot dark matter could have powered stars to shine 10 billion times as bright as our sun. [PNAS→](   [Chemically Induced Reprogramming to Reverse Cellular Aging]( It appears possible to rejuvenate cells by reversing their age without changing the genome. [Aging→](   [Collective Events and Individual Affect Shape Autobiographical Memory]( How the pandemic changed the way we remember. [PNAS→](   [Oil Lamps, Spearheads, and Skulls: Possible Evidence of Necromancy during Late Antiquity in the Te’omim Cave, Judean Hills]( Locals reported that the spring water that flowed in the cave had healing powers. [Harvard Theological Review→](   [Using Machine Learning to Decode Animal Communication]( Can we interpret what animals mean to “say” when they rely on “visual, acoustic, tactile, chemical, and electrical signals—often in conjunction, and beyond humans’ perceptive capabilities”? [Science→](   [How Old Is Our Universe? New Study Says Big Bang Might Have Happened 27 Billion Years Ago]( It’s a well established finding that the cosmos began 14.6 billion years ago. What evidence could overturn this result? [USA Today→](   [Benjamin Franklin Put Early Anti-Counterfeit Measures in Paper Money]( You couldn’t have asked for a more innovative and industrious founding father. [New Scientist→](   [“They’re Outsmarting Us”: Birds Build Nests from Anti-Bird Spikes]( “Auke-Florian Hiemstra, a biologist who studies how wild animals repurpose human materials, thought he had seen everything.” [The New York Times→]( Experience the endless possibilities and deep human connections that science offers [JOIN TODAY](   Join the F3 Krill Replacement Challenge In [Future of Fish Feed]('s newest aquaculture feed contest, 10 companies will compete for $100,000 by developing the best krill replacement. Registration is open until August 31, 2023. [Join the race]( to replace krill in aquaculture feeds. [REGISTER TODAY](   From The Porthole: short sharp looks at science   NEUROSCIENCE Loss of Smell May Be an Early Sign of Brain Diseases Scientists have learned smell loss can be a diagnostic tool for Parkinson’s and Alzheimer’s. BY KRISTEN FRENCH   It’s summer in San Diego, California, where I live. When I walk down the street, I can smell the delirious musk of jasmine clinging to the air. On a Sunday, my nose picks up the languid smokiness of briquets burning on barbecues, taking me back to decades of yard parties. But given the heat wave descending on the city, the garbage is also throwing off a sickly stench, hinting at decay. These odors are all good signs. We have long known that smell has potent connections to memory and emotion, as the endurance of Proust’s proverbial madeleine moment attests. In fact, the limbic system, including the amygdala and the hippocampus, is responsible for processing memory, emotion, and smell. While Western culture has generally [relegated]( the sense of smell to the lowest rank since the time of Plato, some hunter-gatherer groups such as the Semaq Beri of the Malay peninsula have more words for smells than for color hues. Now, researchers are learning that the sense of smell is critical as a marker of brain health and disease. Over the past decade, loss of smell—known as hyposmia—has emerged as an early indicator of several neurodegenerative disorders, according to a recent International Journal of Molecular Science [review]( of 20 papers. The high prevalence and early onset of smell loss, along with the development of sensitive olfactory tests, has raised interest in it as a diagnostic tool for Parkinson’s disease and Alzheimer’s disease, in particular. But loss of smell also afflicts people with [Huntington’s disease](, [multiple sclerosis](, and [mild cognitive impairment](. Catching these diseases early by testing for powers of smell could give patients a head start on neuroprotective and disease-modifying therapies. The power of the nose peaks in middle age, around age 40. The connection between odor detection and brain health makes sense. Our sense of smell begins in the nose and then proceeds directly to the olfactory bulb at the base of the brain. It’s the first sensory structure we have that provides direct contact with sensory stimuli and environmental pathogens in the air. Experimental evidence suggests olfactory bulb neurons play a key role not just in the loss of smell but also in the early stages of brain disease. Some researchers at the University of Padova in Italy are looking at how the sudden smell loss characteristic of COVID-19 [connects]( with Parkinson’s disease. Viral infections, like COVID-19, and regional inflammatory processes may trigger defective proteins to aggregate, a feature of Parkinson’s, and lead neurons to subsequently degenerate, the researchers hypothesize. Certain psychiatric diseases are also associated with smell dysfunction: Schizophrenia patients have shallower nasal cavities and smaller olfactory bulbs than healthy individuals, as well as other nasal abnormalities that Alzheimer’s patients also experience. [Like the story? Join Nautilus today]( Not everyone with smell loss will develop brain disease. The acuity of our sense of smell declines as we age but follows a different trajectory from that of some other cognitive and perceptual abilities. While short-term memory peaks at age 25, for example, the power of the nose peaks in middle age, around age 40, and then gradually begins to slip. Age-related loss of smell is greater in men than women, and women have a higher total number of olfactory bulb cells than men—at least 50 percent more, on average, [research]( suggests. Aside from its connection to neurodegeneration, smell is also a powerful marker of overall health and mortality risk. In one longitudinal [study]( of 1,162 healthy older people (without dementia) the mortality rate over a four-year period was 45 percent for those with the lowest baseline olfactory test scores, compared to 18 percent for those with the highest scores, even after controlling for age and other factors. It is surprisingly difficult to know when we have lost our sense of smell: About 70 percent of people living with a loss of smell don’t realize it until they’re tested. (If you’re curious, you can take a simple scratch and sniff [smell test]( to find out how well your nose performs, and depending on the results, you could receive an invite to join a research study sponsored by the Michael J. Fox Foundation.) There may be more truth than we realized to the saying, “Follow your nose.” Lead image: Lightspring / Shutterstock More from The Porthole: • [Requiem for the foghorn]( • [This WWII story made us better thinkers](   P.S. Thomas Kuhn, who coined “paradigm shift” in his book The Structure of Scientific Revolutions, was born on this day in 1922. He once got so angry with a student of his that [he threw an ashtray at him](. That student was Errol Morris, who would go on to become a celebrated documentary filmmaker. Morris titled his recent book about Kuhn The Ashtray. “He got angrier and angrier as I was questioning the whole basis for The Structure of Scientific Revolutions,” Morris told Nautilus. He came away with the sense that he was [undermining a cult leader](.   Today’s newsletter was written by Brian Gallagher   BECOME A MEMBER [Celebrate Cormac McCarthy]( In 2016, Nautilus published the first and only piece of nonfiction by the late, great American novelist Cormac McCarthy. A meditation on the nature of the unconscious mind and the origins of language, [“The Kekulé Problem”]( is a song to the mysteries of the unconscious, a dreamland that feeds solutions to our conscious minds, as it did when it offered the configuration of the benzene molecule to 19th-century chemist August Kekulé while he slept. The idea that language is the root of thinking, that it evolved to bond humans, seemed to offend McCarthy. Language wasn’t a biological invention; it was a human invention. Let’s say language emerged 100,000 years ago, as McCarthy’s “influential persons” suppose. That’s an eyeblink to the 2 million years “in which our unconscious has been organizing and directing our lives. And without language you will note.” The artist doesn’t want you to live on the surface. McCarthy’s fiction is a portal into the unconscious where primeval feelings dwell. [The essay]( offers a rare, if singular, insight into McCarthy’s thinking during his time at the Sante Fe Institute, where he spent decades conversing with scientists to microscopically probe the nature of consciousness itself. [Read "The Kekulé Problem"]( Thanks for reading. [Tell us](mailto:brian.gallagher@nautil.us) your thoughts on today’s note. Plus, [browse our archive]( of past print issues, and inspire a friend to sign up for [the Nautilus newsletter](. [Facebook]( [Twitter]( [Instagram]( Copyright © 2023 NautilusNext, All rights reserved. You were subscribed to the newsletter from nautil.us. Our mailing address is: NautilusNext 360 W 36th Street, 7S, New York, NY 10018 Don't want to hear from us anymore? Click here to [unsubscribe](.