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Neuroscience: Humans without a sense of smell breathe differently
Humans without a sense of smell have altered breathing patterns compared to those who can smell, according to a paper published in Nature Communications. The findings could provide insight into why some individuals who lose their sense of smell may experience certain health conditions.
A loss of the sense of smell (known as anosmia) is commonly associated with depression, personal isolation and emotional blunting (a reduced emotional response). In addition, anosmia has been linked to reduced life expectancy compared to those with a functioning sense of smell. Given the complex interconnections between smelling and breathing, Lior Gorodisky, Noam Sobel and colleagues hypothesise that anosmia could be linked to altered breathing patterns.
The authors assessed 21 people with and 31 without a sense of smell over a 24-hour period and monitored their breathing patterns using a wearable device that measured nasal airflow. They found that whilst all participants breathe at the same overall rate, participants with a sense of smell had added small inhalation peaks within every breath, totalling about 240 more inhalation peaks per hour. These additional inhalation peaks did not occur when participants were placed in an odourless room, suggesting that this difference was related to their sense of smell and may reflect exploratory sniffing. Participants with anosmia did not conduct this exploratory sniffing and had shifts in their overall respiratory pattern, both when awake and asleep.
The authors were also able to predict which participants had a sense of smell with 83% accuracy, based solely on the participant’s breathing patterns. The authors suggest that this change in breathing pattern in anosmic individuals could result in altered brain activity, which could be linked to some mental and physical health conditions observed in those without a sense of smell, particularly depression and anxiety.
The findings highlight how a sense of smell could affect human breathing patterns, which may contribute to the negative health outcomes observed in some anosmic individuals.
