Lack of correlation between CSF glutamate levels and PSQI scores in heavy smokers
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Glutamate is an excitatory neurotransmitter in the central nervous system that participates in initiation and maintenance of sleep and wakefulness. The mechanisms involved occur in the brainstem, lateral hypothalamus, and basal forebrain. Our previous study suggested that higher levels of glutamate in cerebrospinal fluid (CSF) contributed to poorer sleep quality. Smoking has been shown to be harmful to sleep quality. In the present study, we recruited non-smokers and heavy smokers and measured the concentration of CSF glutamate in order to investigate the associations among smoking status, sleep quality, and CSF glutamate levels.
We recruited 147 men (n = 68 non-smokers, 30.31 ± 9.10 years; n = 79 heavy smokers, 34.54 ± 10.71 years). Glutamate concentrations in CSF were measured by spectrophotometry, and subjective sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI).
PSQI total scores were significantly higher in heavy smokers than that in non-smokers (p < 0.001). Glutamate concentrations in CSF were lower in heavy smokers than that in non-smokers (p < 0.001). CSF glutamate levels positively correlated with PSQI total scores in the non-smokers group (r = 0.313, p = 0.011, effect size = 0.324). No correlation was found between CSF glutamate levels and PSQI total scores in the heavy smokers group (p > 0.05). Multivariable linear regression analysis showed that years of smoking was contributed to the PSQI total scores (p = 0.008), and cigarettes smoked per day contributed to the decreased CSF glutamate levels in heavy smokers (p = 0.001).
Poorer subjective sleep quality and lower CSF glutamate concentrations were observed in the heavy smokers group than in the non-smokers group. In addition, lack of correlation was observed between CSF glutamate levels and PSQI scores in the heavy smokers.
KeywordsCerebrospinal fluid Glutamate Sleep Heavy smoking
This work was supported by the Technology Support Project of Xinjiang (2017E0267), Opening Project of Zhejiang Provincial Top Key Discipline of Pharmaceutical Sciences funding, Projects of Medical and Health Technology Program in Zhejiang Province (2017KY720) and Basic and public research project of Zhejiang province (LGF18H020001), Advanced key Scientific and Technological Programs of Ningbo (2013C51009), Public Technology Application Research Project of Zhejiang (2017C35002), and Project of Zhejiang Medical and Health Platform Plan (2016DTA009). The sponsor had no role in the design or conduct of this research.
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Conflict of interest
All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge, or beliefs) in the subject matter or materials discussed in this manuscript.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (the Human Ethics Committee of Inner Mongolia Medical University) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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