Abstract
Purpose: :
To evaluate morning salivary cortisol as a disease biomarker in conjunction with measures of sleep quality among African American individuals with COAG.
Methods: :
Cross-sectional analysis of morning (AM) salivary cortisol in conjunction with evaluation of sleep quality among African Americans over age 40 of either gender with COAG documented by visual field and/or optic nerve abnormality. Subjects with a history of diabetes mellitus or systemic corticosteroid use were excluded from study. Morning salivary cortisol specimens were collected following an 8 hour fast at approximately 9:00 AM in conjunction measurement of intraocular pressure. Salivary cortisol level was determined by ELISA methodology. Sleep quality was assessed at the time of salivary specimen collection using the Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleep Survey.
Results: :
Fifteen female and 6 male subjects were enrolled for study with an age range from 43-91 years (median age 71). Salivary cortisol levels ranged from 3.94-37.34 ng/mL (median 17.45 ng/mL). HIstorical data of AM salivary cortisol levels among older adults ranges from 1.8-5.3 ng/mL. Score on the PSIQ ranged from 2-19 (median 9). Epworth scores ranged from 0-16 (median 5). With α = 0.05, Pearson correlation between levels of AM salivary cortisol and intraocular pressure or age was not significant (p = 0.3985 and 0.3348, respectively). Spearman rank correlation between AM salivary cortisol and performance of either the PSQI or Epworth survey was also not significant (p = 0.1545 and 0.0970 respectively). No relationship was found between age and score of the PSQI (p = 0.3191). Notably, the 25th percentile score of the PSQI was 5. Assuming PSQI scores over 5 are indicative of poor sleep quality, 75% of the study participants were found to have abnormal sleep measures. Results of the Epworth sleep survey were less robust.
Conclusions: :
Compared to historical controls, African Americans with documented COAG demonstrated abnormal, albeit variable, AM salivary cortisol levels that correlate poorly with IOP, age and sleep status. Sleep abnormalities are highly prevalent among African American individuals with COAG regardless of age. Study results support the notion that circadian light-dark sleep cycles are disrupted in subjects with COAG presumably due to disturbance of intrinsically photosensitive retinal ganglion cell function. Further study is necessary to clarify salivary cortisol as a clinical biomarker in COAG management..
Keywords: clinical (human) or epidemiologic studies: risk factor assessment • ganglion cells • circadian rhythms