During the day, the volunteers stored the T-shirts in sealed plastic bags; avoided spicy foods, cigarettes and alcohol; and showered with odorless shampoo and soap. A different group of 41 young men and women volunteered their noses, taking a big whiff of the air at the top of a jar while blindfolded and rating both the intensity and pleasantness of the odor. Sometimes volunteers had to choose which of two odors most likely came from the older volunteer.
Other times the volunteers had to label different jars "young," "middle-age" or "old-age. Middle-aged man musk took top prize for intensity and unpleasantness, whereas volunteers rated the odors of middle-aged women most pleasant and whiffs of old man as least intense.
When the volunteers compared two jars containing pads from different age groups, they reliably recognized that the odors were different, but they were not particularly adept at deciding which scent came from the older person.
When volunteers attempted to label several different jars by age group, they also often failed to correctly identify odors from the young and middle-aged—but they were much more successful at picking out the jars containing pads soaked in elderly sweat. Old people smell was often instantly recognizable. Together, the evidence indicates that people recognize a characteristic "old people smell" not because of the aroma's intensity or offensiveness, but because of its uniqueness compared to the body odors of younger people.
The chemical, which the researchers described as having an "unpleasant grassy and greasy odor," might be "a major cause of the deterioration in body odor that has been observed with aging"—in other words, the biological explanation for why older people have a characteristic odor.
But the compound has also been linked to the scent of cucumbers and aged beer, which are not distasteful to most people; others have compared old people smell to old book smell , which most people find benign at worst and enjoyable at best. Compared with many other animals, humans have a lousy sense of smell. Determining exactly how people change their behavior based on one another's scents— or possibly pheromones —has frustrated and challenged scientists. Still, some evidence suggests that subtle chemical communication, much of it subconscious, helps people recognize family, changes women's reproductive cycles and makes it easier to empathize with others.
But no one really knows why animals or people have this ability. Ferris Jabr is a contributing writer for Scientific American.
As a result, the researchers could investigate how genes related to product usage. About 98 percent of the women had the gene for smell-producing armpits. Of those, 95 percent used deodorant on a regular basis. But of the the non-odor producing women, over three-quarters still used deodorant daily.
That suggests the majority of women are using a product every day, when they have no need to, Day said. Though the team didn't look at men, they think the results should generalize. Other studies have found that men in general are slightly less fastidious in their deodorant use, Day said. Because the study didn't intend to look at deodorant use, the researchers can't tease out why smell-free women continue to slather on the odor-reducing product.
But one possibility is that social pressure or conformity plays a large part in some of our most common hygiene routines, Day said. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Already a subscriber? For instance, levels of corticosterone in the blood are elevated during an immune response, and androgens are reduced. Over recent years, scientists have investigated whether dogs might be able to use their impressive powers to detect cancer. The findings are not without controversy , but some studies have yielded impressive detection rates.
For example, in one study , four trained sniffer dogs were able to detect lung cancer in breath samples from people with accuracy rates of 68 to 84 percent. Another study demonstrated that an 8-year-old female black Labrador Retriever could correctly diagnose more than 90 percent of colorectal cancers from breath and stool samples. She was even able to detect early cancers. Although training dogs to be ever more accurate might be useful in diagnosing cancers early, it is not a perfect solution; it involves intense, expensive training and the time of an experienced handler.
Also, there is variability in accuracy between dogs, and even in the same dog on different days. Some studies have also produced less impressive, almost random results. Electronic noses have come on leaps and bounds in recent years and are now capable of detecting and recognizing a range of specific flavors and odors.
They are already used in some industrial processes. Most electronic noses use sensor arrays that react to volatile compounds as they make contact; the sensors physically change as they interact. These changes are digitally recorded and pumped through statistical models. There is hope that electronic noses will, one day, be able to detect bacteria and distinguish MRSA in hospital ventilation systems. Scientists have also tried to use them to detect lung cancer from expelled breath and to identify brain tumors.
Others have tried to use electronic noses to detect kidney disease, bowel disease, and diabetes from urine. Results have varied, but a nonintrusive way to detect medical conditions at an early stage would be of huge benefit. Sadly, anosmia and hyposmia — that is, a partial loss of sense of smell — have received relatively little research. They are not considered critical and have therefore attracted less interest and funding.
However, impaired olfactory function affects an estimated 2. A reduced sense of smell can be caused in a number of ways, including head trauma, viral infections, nasal obstruction, some medications, and neurologic disorders.
And it is far from a harmless annoyance. They found that more than a third of people with a reduced sense of smell had experienced a related hazardous event. These included:. In some individuals , anosmia can lead to anorexia because there is no pleasure in eating food. At the other end of the scale, some people with hyposmia become obese because salty, deep-fried foods are the only ones that seem appealing.
Also, because taste stimulates salivary and pancreatic activity, a reduced sense of smell can interfere with digestion. Due in part to the aging population, dementia is an ever-increasing problem. And unfortunately, dementia is difficult to treat and cannot be cured. The emphasis is on treating the symptoms, slowing the disease, and, wherever possible, catching it early.
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