Modifiable Environmental Exposures May Contribute To Olfactory Impairment: JAMA

Olfactory dysfunction affects millions of people worldwide. This sensory impairment is associated with neurodegenerative disease and significantly decreased quality of life. Exposure to airborne pollutants has been implicated in olfactory decline, likely due to the anatomic susceptibility of the olfactory nerve to the environment. Historically, studies have focused on occupational exposures, but more recent studies have considered effects from exposure to ambient air pollutants. For the same, researchers of the University of Wisconsin-Madison conducted a study to determine the 10-year cumulative incidence of olfactory impairment and evaluate potentially modifiable risk factors for impairment including exposure to cadmium, lead, and tobacco smoke.

Researchers assessed the data from the Beaver Dam Offspring Study, a longitudinal cohort study of sensory health and ageing in a general population. They examined the data at baseline (2005-2008), 5 years (2010-2013), and 10 (2015-2017) years. They included a total of 2312 participants without olfactory impairment at baseline and with olfaction data available at the 5- and/or 10-year examination and analyzed them from April 28, 2020, to January 8, 2021. The major outcome assessed was olfactory impairment which was measured by the San Diego Odor Identification Test. They used Cox discrete-time proportional hazards analyses to model the associations between baseline covariates, including blood cadmium and lead levels and tobacco smoke exposure, and the 10-year cumulative incidence of olfactory impairment.

Key findings of the study were:

• Upon analysis, they noted that the 10-year cumulative incidence of olfactory impairment was 4.6% and it increased with age.
• They modelled cadmium and tobacco smoke exposure separately due to high collinearity.
• In a multivariable-adjusted model, they found that higher blood cadmium level (hazard ratio [HR], 1.70) was associated with the 10-year cumulative incidence of olfactory impairment.
• They also found that high exposure to tobacco smoke as a current smoker (HR, 2.94 smokers vs no exposure) or from environmental tobacco smoke (HR, 2.65 high vs no exposure) was associated with an increased risk for developing olfactory impairment.
• However, they found no significant association between blood lead levels and olfactory impairment.

The authors concluded, "Results of this longitudinal cohort study suggest that modifiable environmental exposures may contribute to olfactory impairment that occurs with ageing. Identification of modifiable risk factors for olfactory impairment may lead to prevention strategies that have the potential to reduce the burden of olfactory impairment at older ages."

For further information:

https://jamanetwork.com/journals/jamaotolaryngology/article-abstract/2777615