Changes in breathing in people without sense of smell may explain health problems

Research has revealed that people with anosmia have altered breathing patterns, which may explain the link between anosmia and related health conditions.

In a recent study published in nature communications, Researchers investigated the breathing patterns of participants with and without congenital anosmia (CA, anosmia) using a wearable device that recorded nasal airflow over a 24-hour period.

They found that nasal airflow patterns were significantly altered in individuals with anosmia, and that these patterns could classify anosmia with 83% accuracy based on respiratory tracking alone.

background

Anosmia, which affects up to 15% of the population and is prevalent in states such as California due to the coronavirus disease 2019 (COVID-19), can lead to life-threatening problems such as depression, emotional blunting, and eating problems. leading to a significant decrease in quality. It also increases the risk of hazards such as smoke, leading to higher mortality rates for the elderly. Despite being considered unimportant, the sense of smell has a significant impact on human behavior, including social interactions.

Additionally, your sense of smell influences your breathing, as smells shape your breathing patterns. This link between smell and breathing suggests that anosmia can interfere with normal breathing and cause a variety of negative health effects, including shortened lifespan.

Therefore, researchers in the present study focused on olfaction-related breathing changes over a 24-hour period, using a wearable device to compare the nasal airflow patterns of anosmic participants with those of normal controls.

About research

This study included 21 anesthetized participants (mean age 32 years, 8 women) and 31 normal participants (mean age 28 years, 19 women). Congenital anosmia was confirmed by nasal endoscopy, medical history review, and scoring for olfactory impairment on the University of Pennsylvania Smell Identification Test (UPSIT). Magnetic resonance imaging scans revealed that participants with anosmia had no or no olfactory bulb. Normal subjects were healthy people with no problems with their sense of smell or respiratory system. Participants self-rated their sense of smell, with anosmia rating averaging 1.1 and normal olfactory rating averaging 7.5.

Nasal airflow was recorded using a wearable device named a “nasal holter” that measures airflow through each nostril individually and records data at 6 Hz. Participants kept a daily diary to record their sleep and wake times. Airflow data were divided into 5-min blocks labeled “sleep” or “wake” and analyzed using MATLAB (Mathematics Institute) to extract respiratory features. Inhalation peaks were calculated using a peak detection algorithm. Statistical analysis included the use of repeated measures analysis of variance, Student's analysis of variance. t– Testing and bootstrapping estimated effect sizes using Cohen's D and Bayes factors to compare models.

Results and discussion

Both people with and without anosmia were found to breathe at the same overall rate, showing a significant effect of arousal on breathing rate (slowing down during sleep). However, significant differences were found between apnea and normal participants in 8 out of 27 respiratory parameters.

Normal individuals had a higher frequency of nasal inhalation peaks during wakefulness, with anosmic individuals averaging 23.8 IPPM (inhalation peaks per minute) versus 19.5 IPPM.

When tested in an odorless environment, the IPPM of the normal group was similar to that of the anosmic group, suggesting that the increased inhalation peak in the normal group is related to interaction with the olfactory environment rather than fixed differences in breathing patterns. It was suggested that this is likely.

Additionally, anosmic individuals had a higher proportion of breathing with inhalation pauses during waking hours (81%) compared to normosmic individuals (75%, P = 0.004). During sleep, anosmic individuals showed a higher coefficient of variation (CoV) of inhaled volume compared to controls (P = 0.004). Additionally, peak expiratory flow during wakefulness was decreased in anosmia compared to controls.

Taken together, these results indicate that anosmia is characterized by increased inhalation pauses, decreased expiratory peak flow during wakefulness, and greater fluctuations in inhalation volume during sleep.

The overall accuracy of the classification analysis was 83%, with a true positive rate of 67% and a true negative rate of 94%. This classification does not rely solely on IPPM, and even when this parameter was omitted, an accuracy of 81% was obtained. However, removing this parameter reduced the accuracy to 62%, which made it dependent on the inhaled dose of CoV during sleep. Differences in breathing patterns between anosmia patients and controls during sleep are unlikely to be due to olfactory responses, and we found no evidence of altered nasal cycles in anosmia.

This study provides evidence that people with congenital anosmia have unique breathing patterns compared to controls. This difference has previously gone unnoticed due to the use of low-pass filters (3 Hz) in traditional long-term respirometry methods such as piezoelectric belts and plethysmography. However, this study is limited by small sample size, lack of oral airflow measurements, lack of formal validation of normal olfactory sense in controls, and lack of data on acquired olfactory disorders.

conclusion

In conclusion, the results of this study suggest that loss of smell affects breathing and broader respiratory function. In the future, research may explore broader health effects associated with anosmia, such as a higher risk of death in acquired anosmia.