A natural decline to a person's sense of smell as they age may cause their libido to fall, research suggests.
Smell plays a "uniquely strong role in sexual motivation", but often becomes muted over time due to a loss of nerve endings or mucus production in the nose.
To better understand the impact of this, scientists from the University of Chicago analysed the "olfactory function" of more than 2,000 older adults, who were also surveyed on their "sexual thoughts and activity".
Results suggest a reduction to an elderly person's sense of smell is linked to a 7% drop in their "sexual motivation" and an 11% decrease to their "emotional satisfaction" when it comes to intimacy.
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With a loss of smell "affecting sexuality in older adults", the scientists hope medics will treat sensory reduction with the aim of boosting a patient's overall quality of life.
The scientists analysed a group of community-dwelling older adults – average age 72 – from across the US, who took part in the National Social Life, Health and Aging Project.
The team measured how sensitive the participants were to the scent of n-butanol, a chemical often added to protective resins.
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The older adults were also asked to identify the odours on "Sniffin Sticks", a validated method of assessing smell.
The survey asked the participants about their sex life, including how satisified they were by their most recent encounter.
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The results, published in The Journal of Sex Medicine, reveal a decline in "olfactory function" was linked to a reduction in the participants' "sexual motivation" and their "emotional satisfaction with sex".
This remained true after the scientists accounted for the participants' age, gender, race, level of education, underlying health and any depression diagnosis; all of which may affect libido to some extent.
A reduction in smell was not linked to "decreased frequency of sexual activity or physical pleasure", however.
"Olfactory dysfunction in older US adults is associated with decreased sexual motivation and emotional satisfaction, potentially due to evolutionarily-conserved neurological links between olfaction and sexuality," concluded the scientists.
"Potentially treatable causes of sensory loss should be addressed by clinicians to improve quality of life."
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