Humans are not particularly known for their acute sense of smell, like dogs for example. However, a recent study suggests we can tell the age of older people based on their body odour.
"Humans are actually quite good at sniffing around," says study lead Johan Lundström, a researcher at the Monell Chemical Senses Center in Philadelphia, Pennsylvania. "The problem is that our nose is a little higher up from the ground, and the human brain is wired to not pay attention to odors."
The study -- published Wednesday in the Public Library of Science's open-access online journal PLoS ONE -- involved having volunteers sniff the clothing of people from three different age groups.
In this somewhat sickening experiment, researchers had 41 healthy donors sleep for five nights with nursing pads sewn into t-shirt armpits. The donors were grouped into three categories — the young group aged 20 to 30, the middle-aged group from 45 to 55 and the old-age group from 75 to 95.
They washed their sheets, towels and bedclothes in the same unscented detergent, showered with the same unscented soap, and didn't drink alcohol, smoke or eat spicy foods or anything known to change body odour.
Then a brave group of 41 evaluators agreed to sniff the odors and rate their intensity, their level of pleasantness (or unpleasantness), and take a guess on what age group the smells emanated from.
While the judges were not so good at distinguishing the odors of those in their 20s from those in middle age, they were quite accurate at predicting which scents came from the oldest group.
Contrary to the bad reputation that older people have when it comes to smell, they fared quite well compared to their younger counterparts. Their odors were less intense, and less offensive than in the other groups.
"We definitely have a characteristic old-person's odor," says Lundström. "But it doesn't smell that negative."
He thinks that other things, like visual cues, might explain why we think older people smell worse than their younger peers.
When we see something, it can change our interpretation of its scent. Try getting someone to smell blue cheese with a blindfold, and asking them about whether they smell dirty socks. They likely won't find the strong smell agreeable.
But unlike blue cheese, it seems that humans get less smelly as we age.
And while women's smells throughout the age categories hovered around neutral for intensity and pleasantness, men did not do so well.
"Young guys are stinky and middle-aged men are even more stinky," says Lundström.
Watch the video below about how Canada's population is aging very quickly according to census data.