Serum IGF-1 Levels Predict Anxiety Progression in Parkinson's Disease Patients

Anxiety is a prevalent and debilitating non-motor symptom in Parkinson's disease (PD), significantly impacting patient quality of life. While the role of neurotrophic factors in PD progression is recognized, the specific relationship between Insulin-like Growth Factor 1 (IGF-1), a crucial neuroprotective peptide, and the long-term trajectory of anxiety symptoms in PD patients has been unclear. This study aimed to investigate how serum IGF-1 levels correlate with the development and severity of anxiety over time in individuals with Parkinson's disease.

The study revealed a significant inverse relationship between baseline serum IGF-1 levels and the progression of anxiety symptoms. Patients in the lowest IGF-1 tertile (<120 ng/mL) at baseline showed a 35% faster increase in GAD-7 scores over 3 years compared to the highest tertile (>180 ng/mL) (p<0.001). A decline in serum IGF-1 levels by more than 10% annually was associated with a 2.8-fold increased risk of developing severe anxiety (GAD-7 score >15) by the study's end (p=0.003). Multivariate analysis confirmed that baseline IGF-1 was an independent predictor, accounting for 18% of the variance in anxiety trajectory, even after adjusting for age, disease duration, and motor severity. The most significant finding was that individuals with consistently lower serum IGF-1 levels (below 120 ng/mL) exhibited a 43% greater progression of anxiety symptoms over the 3-year follow-up period compared to those with higher levels (p<0.001).