Study finds olfactory impairment to increase the risk of cognitive decline

There were 37,783 participants and 48 papers in this research. When compared to people with normal olfaction, OI patients had a 2.06-fold higher risk of any CD (risk ratio [RR] = 2.06; 95% CI = 1.87‒2.26, I2 = 0%). In comparison to individuals with mild OI (RR = 1.51; 95% CI = 1.23‒1.85, I2 = 0%), those with severe OI had a greater risk of any CD (RR = 2.60; 95% CI = 2.12‒3.20, I2 = 0%).

Every 10% drop in olfactory score (RR = 1.18; 95% CI = 1.14‒1.22, I2 = 24%) and every point drop on the Sniffin' Sticks Odor Identification Test (RR = 1.15; 95% CI = 1.11‒1.18, I2 = 0%) raised the probability of any CD by 18%. These findings held up well to additional examinations. The PAF of incident CDs linked to OI was 18%.

Overall, OI with higher category severity and deteriorating olfactory scores was linked to a higher risk of CD, according to a positive categorical and continuous dose-response association. Cognitive screening should be advised for individuals with chronic OI, and OI may be included as a component of early cognitive screening in high-risk patients.

Source:

Yeo, B. S. Y., Song, H. J. J. M. D., Tan, B. K. J., Suresh, A., Ho, O. T. W., Chan, J. H., Gao, E. Y., Tan, C. J.-W., Teo, C. B., Chen, C. L.-H., Tay, L., Lamoureux, E. L., Hummel, T., See, A., Xu, S., Toh, S. T., Charn, T. C., & Teo, N. W. Y. (2025). Olfactory impairment and incident cognitive decline: A systematic review and meta-analysis. International Forum of Allergy & Rhinology, e23635, e23635. https://doi.org/10.1002/alr.23635