Imagine your sense of smell as a reliable detective, searching for clues about your overall health. In the case of Parkinson’s disease (PD), this detective often loses its way. A recent study investigated how changes in olfaction, or the sense of smell, relate to both motor and non-motor symptoms in PD. By studying two groups – those with anosmia (a complete lack of smell) and those without – researchers discovered some intriguing findings. The group with anosmia, despite being older and having a longer disease duration, showed stable olfactory function over time. However, the non-anosmia group experienced a significant decrease in their sense of smell. Interestingly, this decline did not seem to be related to cognitive decline but rather to motor progression. These findings suggest that while anosmia may be a marker of advanced PD, individuals with a shorter disease course can still experience a regression in their sense of smell. If our olfactory detective is feeling out of sorts, it may be an early sign that motor symptoms are on the horizon. To uncover all the details, be sure to dive into the full research article!

IntroductionHyposmia is a common prodrome in patients with Parkinson’s disease (PD). This study investigates whether olfactory changes in PD differ according to the degree of olfactory dysfunction and whether there are changes in motor and non-motor symptoms.MethodsThe 129 subjects with PD were divided into two groups: anosmia and non-anosmia. All cases were reassessed within 1–3 years after the initial assessment. The assessment included the MDS-Unified PD Rating Scale (MDS-UPDRS), the University of Pennsylvania Smell Identification Test (UPSIT), Beck’s Depression Inventory-II (BDI-II), Montreal Cognitive Assessment (MoCA), and equivalence dose of daily levodopa (LEDD). The generalized estimating equation (GEE) model with an exchangeable correlation structure was used to analyze the change in baseline and follow-up tracking and the disparity in change between these two groups.ResultsThe anosmia group was older and had a longer disease duration than the non-anosmia group. There was a significant decrease in UPSIT after follow-up in the non-anosmia group (β = −3.62, p < 0.001) and a significant difference in the change between the two groups (group-by-time effect, β = 4.03, p < 0.001). In the third part of the UPDRS motor scores, there was a tendency to increase the score in the non-anosmia group compared to the anosmia group (group-by-time effect, β = −4.2, p < 0.038). There was no significant difference in the group-by-time effect for UPDRS total score, LEDD, BDI-II, and MoCA scores.DiscussionIn conclusion, this study found that olfactory sensation may still regress in PD with a shorter disease course without anosmia, but it remains stable in the anosmia group. Such a decline in olfaction may not be related to cognitive status but may be associated with motor progression.

Read Full Article (External Site)