Influence of age, schooling and cognition on olfactory test performance in Parkinson's Disease patients: a case-control study

Resumo

Background: olfactory dysfunction is an early and prevalent non-motor symptom of Parkinson’s disease (PD). However, factors such as age, schooling, and cognition also influence olfactory test performance and are essential for the proper interpretation of results, especially in populations with low educational levels.

Objectives: to evaluate the influence of age, schooling, and cognition on olfactory test performance in Parkinson’s disease patients (PDG) and the control group (CG).

Materials and Methods: this cross-sectional case-control study included 106 participants (53 PDG and 53 CG), aged 60 to 85. All underwent olfactory testing with Sniffin´Sticks-12 (SS-12) and the modified Connecticut Chemosensory Clinical Research Center (mCCCRC) and cognitive screening with the Montreal Cognitive Assessment (MoCA). The PDG was scored by part III of the UPDRS-III and the H&Y scale. Statistical analyses were performed to assess associations between variables.

Results: PDG scored lower on both olfactory tests and on the MoCA. Cognitive performance positively influenced olfactory scores, especially for SS-12 in both groups. Education significantly affected SS-12 and MoCA scores but had no important effect on mCCCRC performance. Age negatively impacted mCCCRC scores in the CG.

Conclusion: although education significantly influenced SS-12 scores, our findings showed that mCCCRC performance was less affected by lower educational levels. This highlights the mCCCRC as a more education-independent olfactory test, suitable for use in populations with limited schooling. Integrating cognitive and olfactory testing may enhance clinical evaluation and monitoring in PD.