Polysomnographic and nocturnal heart rate correlates of cognitive impairment in Parkinson’s disease: a cross-sectional study

Objective To investigate the correlations between cognitive impairment in Parkinson’s disease (PD) and nocturnal video-polysomnography (vPSG) and electrocardiogram (ECG) parameters, evaluating their independent clinical value. Methods We analyzed 84 PD patients divided into normal cognition (PD-NC, n = 27), mild cognitive impairment (PD-MCI, n = 27), and dementia (PDD, n = 30) groups. Clinical scales, overnight vPSG, and electrocardiogram parameters were recorded. Multivariable linear regression was used to evaluate independent factors associated with the Montreal Cognitive Assessment (MoCA) scores. Results As cognitive impairment progressed, REM sleep latency significantly shortened (128.82 ± 117.32 min in PDD vs. 200.54 ± 90.26 min in PD-NC, p = 0.006). Concurrently, mean nocturnal heart rate (65.80 ± 10.80 bpm) and minimum heart rate (50.77 ± 12.51 bpm) were significantly higher in the PDD group than in the other two groups ( p < 0.01). Multivariable linear regression revealed that, after adjusting for age, education, and UPDRS III score, mean nocturnal heart rate remained independently and negatively associated with MoCA scores ( B = −0.158, β = −0.264, t = −3.018, p = 0.003), while REM sleep latency was independently and positively associated with MoCA scores ( B = 0.010, β = 0.192, t = 2.224, p = 0.029). Collinearity diagnostics showed no significant multicollinearity ( VIF : 1.029–1.261). Conclusion Higher mean nocturnal heart rate and shorter REM sleep latency were independently associated with lower global cognitive performance in PD patients. Both measures can be obtained from routine overnight PSG, although their physiological significance remains uncertain. The cross-sectional design and the absence of direct autonomic or cholinergic measurements preclude causal or mechanistic conclusions.