Purpose
To investigate cortisol concentration as a biochemical correlate of chronical psychological stress as a risk factor for progression of keratoconus.
Methods
27 participants were included in this prospective observational pilot study (11 healthy (H) and 16 keratoconus (KC) patients). Hair strands of healthy humans and keratoconus patients were analyzed in order to compare their hair cortisol concentration as the biomarker of stress. Based on an average hair growth rate of 1 cm/month, hair cortisol of a hair segment of 3 cm length is supposed to represent the stress profile of the last three months. We investigated hair strands of a diameter of approximately 3 mm which were taken scalp-near from a posterior vertex position. Cortisol concentrations were determined from the 3 cm hair segment most proximal to the scalp. Cortisol levels were determined in Institute of Biopsychology of the TU Dresden using a commercially available immunoassay with chemoluminescence detection (CLIA, IBL-Hamburg, Germany). Relevant sociodemographic variables were recorded. An objective standardized questionnaire for chronic stress had to be answered using the Trierer Inventar of chronic stress (TICS) screening scale.<br /> Statistical analysis was performed using SPSS: Chi²-test and ANOVA were used to determine which parameters differed between the two groups.
Results
In keratoconus patients hair cortisol concentration was higher than in healthy subjects (37.51±7.0 vs. 20.99±8.2 pg/mg P=0.142). Normal hair cortisol ranges from 5-25 pg/mg, therefore the measured values were close to significance. More pathological increased values were found in the KC than in H (50% vs. 18%; P=0.093) were found. Furthermore patients with KC have a significant higher BMI (27.5 kg/m² vs. 23 kg/m²; P=0.044). No difference was found in age, gender, TICS.
Conclusions
The pilot study showed that increased hair cortisol concentration seemed to be a risk factor for progressive keratoconus and these patients might benefit from avoiding chronical stress.<br /> A larger study with more participants is necessary in order to confirm a possible statistical significance of this hypothesis.