Peripheral Blood Inflammatory Cytokines are Associated with Rapid Eye Movement Sleep Behavior Disorder in Parkinson’s Disease

Investigating the relationship between sleep disturbances and cortical thickness, brainstem volume, amyloid accumulation, and inflammatory markers in Parkinson's disease patients

BACKGROUND

This study aimed to explore the relationship between self-reported sleep disturbances (e.g., insomnia, REM sleep behavior disorder [RBD]) and cortical thickness, brainstem volume, amyloid accumulation, and inflammatory markers in Parkinson's disease (PD) patients.

METHODS

We conducted a cross-sectional study comparing 100 PD patients (observation group) with 100 age-matched controls. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), and serum levels of amyloid-beta (Aβ1-42), α-synuclein, and inflammatory markers (CRP, TNF-α, IL-1β) were quantified.

RESULTS

PD patients exhibited significantly poorer sleep quality (PSQI total score: 2.11 ± 0.27 vs. 0.52 ± 0.02, P < 0.001), reduced parietal cortical thickness (2.68 ± 0.12 mm vs. 3.15 ± 0.18 mm, P = 0.003), and lower brainstem volume (2697.42 ± 147.05 mm3 vs. 3185.16 ± 255.41 mm3, P = 0.007) compared to controls. Biomarker profiling revealed elevated amyloid pathology in PD, with higher serum Aβ1-42 (median [IQR]: 1.98 [1.75-2.22] vs. 1.14 [1.10-1.19], P < 0.001) and α-synuclein (2.03 [1.85-2.22] vs. 1.06 [1.03-1.10], P < 0.001). Proinflammatory markers were markedly increased in PD, including CRP (9.30 [7.85-10.75] vs. 6.30 [5.60-7.10], P = 0.01), TNF-α (372.20 [329.85-414.55] vs. 184.50 [165.20-203.80], P < 0.001), and IL-1β (573.50 [497.15-649.85] vs. 115.40 [101.05-129.75], P < 0.001). Multivariate analysis identified cortical thinning, brainstem atrophy, and IL-1β elevation as independent predictors of sleep disturbances (P < 0.05).

CONCLUSION

These findings highlight the interplay between neuroanatomical changes, amyloid pathology, and systemic inflammation in PD-related sleep dysfunction, suggesting potential therapeutic targets.

Correlation of inflammatory markers with depression and sleep disorders accompanying the prodromal stage of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder with increasing incidence and disability rates globally, placing a heavy burden on patients and their families. In the prodromal phase of PD, nonmotor symptoms, particularly depression and sleep disorders, are frequent, with profound effects on disease progression and patient quality of life. Emerging research highlights the critical role of inflammatory markers-including interleukins and tumor necrosis factor-in the pathogenesis of prodromal PD. These inflammatory mediators participate in neurodegenerative processes and may induce or exacerbate depressive symptoms and sleep disorders by disrupting the function of the hypothalamic-pituitary-adrenal axis and affecting neurotransmitter, including serotonin, metabolism. Understanding their correlations with nonmotor symptoms in prodromal PD remains incomplete, limiting our ability to develop targeted interventions. This comprehensive review aims to investigate the specific correlations between inflammatory markers and nonmotor symptoms-particularly depression and sleep disorders-in prodromal PD. The findings could have important practical applications, potentially leading to the development of new diagnostic tools and therapeutic strategies for managing PD. By identifying and understanding these correlations, healthcare providers may better predict disease progression and implement more effective treatments for nonmotor symptoms in PD.

Neutrophil-to-lymphocyte ratio and longitudinal cognitive performance in Parkinson's disease

OBJECTIVE

Previous studies have suggested a link between peripheral inflammation and cognitive outcomes in the general population and individuals with Parkinson's disease (PD). We sought to test the association between peripheral inflammation, measured by the neutrophil-to-lymphocyte ratio (NLR), cognitive performance, and mild cognitive impairment (MCI) status in individuals with PD.

METHODS

A retrospective, longitudinal analysis was carried out using data from the Parkinson's Progression Markers Initiative (PPMI), including 422 participants with PD followed over 5 years. Cognitive performance was assessed using a neuropsychological battery including the Montreal Cognitive Assessment (MoCA) and tests of verbal learning, visuospatial function, processing speed, and executive function. Mixed-effect regression models were used to analyze the association between NLR, cognitive performance, and MCI status, controlling for age, sex, education, APOE genotype, and motor severity.

RESULTS

There was a negative association between NLR and MoCA, even after adjusting for covariates (b = -0.12, p = 0.033). MoCA scores for individuals in the high NLR category exhibited a more rapid decline over time compared to the low NLR group (b = -0.16, p = 0.012). Increased NLR was associated with decreased performance across all cognitive domains. However, NLR was not associated with MCI status over 5 years of follow-up.

INTERPRETATION

This study demonstrates a link between elevated NLR and cognitive performance in PD, but not with MCI status over 5 years. This suggests that NLR is more strongly associated with day-to-day cognitive performance than with incident MCI, but this requires further study in more heterogeneous cohorts.

The role of peripheral inflammation-related biomarkers in distinguishing Parkinson's disease

BACKGROUND

Peripheral inflammation plays a significant role in Parkinson's disease (PD). Conflicting studies on whether inflammatory indicators in blood could serve as biomarkers to distinguish PD.

OBJECTIVE

Include a wider range of biomarkers and control confounding factors to comprehensively evaluate the value of peripheral inflammation-related indicators.

METHODS

A total of 80 PD patients were recruited and 80 one-to-one matched healthy controls (HCs). The levels of B-cell, T-cell, and natural killer (NK)-cell in blood were measured using flow cytometry. The levels of neurodegeneration-related proteins in serum were detected and clinical blood test results were collected. Multivariable logistic regression analysis was conducted to explore the role of significant variables in PD. Receiver operating characteristic curve analysis was performed to assess the potential value of these variables.

RESULTS

Compared to HCs, PD patients showed lower levels of lymphocyte, B-cell, T-cell, high-density lipoprotein cholesterol (HDL-C) and lymphocyte-to-monocyte ratio, while the levels of neutrophil, NK-cell, β-amyloid40, neurofilament light chain, neutrophil-to-lymphocyte ratio, and neutrophil-to-HDL-C ratio (NHR) were increased. A higher B-cell count was associated with a lower risk of PD, while higher levels of NK-cell and NHR were associated with a higher risk of PD. B-cell, NK-cell and NHR have potential value in distinguishing PD from non-PD. B-cell and NHR levels were significantly correlated with PD dyskinesia scores.

CONCLUSIONS

B-cell, NK-cell, and NHR may potentially contribute to distinguishing PD patients from HCs. There could be a correlation between the number of B-cell, the level of NHR, and the severity of PD dyskinesia.

The neutrophil-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, and neutrophil-to-high-density-lipoprotein ratio are correlated with the severity of Parkinson's disease

BACKGROUND

Inflammation plays a pivotal role in the pathogenesis of Parkinson's disease (PD). However, the correlation between peripheral inflammatory markers and the severity of PD remains unclear.

METHODS

The following items in plasma were collected for assessment among patients with PD (n = 303) and healthy controls (HCs; n = 303) were assessed for the neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR) and neutrophil-to-high-density-lipoprotein ratio (NHR) in plasma, and neuropsychological assessments were performed for all patients with PD. Spearman rank or Pearson correlation was used to evaluate the correlation between the NLR, the LMR and the NHR and the severity of PD. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic performance of the NLR, LMR and NHR for PD.

RESULTS

The plasma NLR and NHR were substantially higher in patients with PD than in HCs, while the plasma LMR was substantially lower. The plasma NLR was positively correlated with Hoehn and Yahr staging scale (H&Y), Unified Parkinson's Disease Rating Scale (UPDRS), UPDRS-I, UPDRS-II, and UPDRS-III scores. Conversely, it exhibited a negative relationship with Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores. Furthermore, the plasma NHR was positively correlated with H&Y, UPDRS, UPDRS-I, UPDRS-II and UPDRS-III scores. Moreover, negative associations were established between the plasma LMR and H&Y, UPDRS, UPDRS-I, UPDRS-II, and UPDRS-III scores. Finally, based on the ROC curve analysis, the NLR, LMR and NHR exhibited respectable PD discriminating power.

CONCLUSION

Our research indicates that a higher NLR and NHR and a lower LMR may be relevant for assessing the severity of PD and appear to be promising disease-state biomarker candidates.

Neutrophil to lymphocyte ratio in parkinson's disease: a systematic review and meta-analysis

BACKGROUND

The goal of this research was to explore the role of Neutrophil to lymphocyte ratio (NLR) in Parkinson's disease (PD).

METHODS

From inception to 4 June 2023, PubMed, Web of Science, and ProQuest were searched for papers comparing NLR in PD to healthy individuals. Standardized mean difference (SMD) with a confidence interval (CI) of 95% were calculated.

RESULTS

A random-effect model revealed that PD patients had elevated NLR values compared to healthy individuals (SMD = 0.81, 95% CI = 0.47 to 1.14, P < 0.001). The results of subgroup analysis were as follows: (1) study design: We observed that patients with PD had higher levels of NLR than healthy controls in either retrospective (SMD = 1.12, 95% CI = 0.58 to 1.66, P < 0.001) or prospective (SMD = 0.43, 95% CI = 0.18 to 0.68, P = 0.001) studies. (2) Ethnicity: We noticed that individuals with PD had higher levels of NLR than healthy controls, whether they were East Asian (SMD = 0.93, 95% CI = 0.22 to 1.63, P = 0.010) or Caucasian (SMD = 0.75, 95% CI = 0.40 to 1.10, P < 0.001).The pooled sensitivity of NLR in the prediction of PD was 0.67 (95% CI = 0.61-0.73), and the pooled specificity was 0.66 (95% CI, 0.61-0.70).

CONCLUSIONS

Increased levels of NLR is highly related with the presence of PD. Further research is needed to determine the potential clinical benefits of this simple and low-cost biomarker in the PD diagnosis.