Lower calcium levels in hair of Parkinson’s disease patients are associated with presence of sleeping disturbances

ABSTRACT

Objectives: To investigate the correlation between sleep disorders and the concentrations of three metals analyzed from hair samples of PD patients.The hypothesis of an involvement of an imbalance of metals in the development of Parkinson’s Disease (PD) has been strengthened by several clinical chemistry studies. Interestingly, while sparse, some studies have correlated the imbalance of metals in PD patients with comorbidities present in this disease. Although not all PD sufferers present sleep disturbances, significant disorders of sleep are common in this population. Methods: Sleep evaluation was divided into three parameters: sleep quality, excessive daytime sleepiness and clinically probable REM Sleep Behavior Disorder. Flame atomic absorption spectrometry (F AAS) was used to assess the concentrations of calcium, iron and zinc in hair samples collected from a population of PD patients registered in a Brazilian city and from controls (a total of 53 subjects). All subjects lived within a restricted geographical region and were exposed to similar environmental conditions. Results: PD patients with poor sleep quality and excessive daytime sleepiness exhibited significant differences in concentrations of calcium, but not iron or zinc when compared to levels found in controls and PD patients who do not report these sleeping problems. Discussion: Our data suggest that different subgroups of PD patients exist, and clinical chemistry could be useful as a biomarker for these subgroups, which needs to be confirmed in a larger patient population. Further, our data raise the question regarding whether normalization of calcium levels could improve the sleep quality and somnolence in PD patients.

KEYWORDS:

• Metal imbalance
• neurodegenerative disease
• sleep disorder
• REM Sleep Behavior Disorder
• Flame atomic absorption spectrometry
• sleep quality
• sleep evaluation
• comorbidities
• biomarker

Acknowledgement

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brazil for funding support to Ph.D Grant to Altair Brito dos Santos.

Disclosure statement

All authors have read the journal’s authorship agreement, and the authors declare no conflict of interest.

Author Contributions

Altair Brito dos Santos Conceptualization; Data curation; Formal analysis; Funding acquisition; Investigation; Methodology; Roles/Writing - original draft; Writing - review & editing.

Marcos A Bezerra Conceptualization; Funding acquisition; Investigation; Methodology; Project administration; Resources; Supervision; Writing - review & editing.

Marcelo E Rocha Data curation; Formal analysis; Methodology; Project administration; Supervision; Writing - review & editing.

George E Barreto Conceptualization; Formal analysis; Supervision; Writing - review & editing

Kristi A Kohlmeier Formal analysis; Funding acquisition; Investigation; Methodology; Supervision; Roles/Writing - original draft; Writing - review & editing.

Data availability statement

Data will be available upon reasonable request.

Ethics approval

The Research Ethics Committee of Bahia Southwest State University approved the protocol for this study on 4 March 2015 under Protocol number: 38942814.1.0000.0055, which is available on the Plataforma Brazil website.

Informed consent

Patients and controls included in the study read and signed the informed consent form approved by the local Ethics Committee.

Additional information

Funding

This work was financially supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brazil [Grant Number 99999.012934/2013-05]. The funding source(s) had no involvement, in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication.