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Factors Associated with Increased Risk for Clinical Insomnia in Patients with Postherpetic Neuralgia: A Retrospective Cross-Sectional Study.

OBJECTIVE
To determine the risk factors associated with clinical insomnia in postherpetic neuralgia (PHN) patients.


DESIGN
A retrospective cross-sectional study.


SETTING
Outpatient department for interventional pain management at a university hospital.


SUBJECTS
A total of 111 patients with PHN satisfied the study inclusion criteria and were included in the analyses.


METHODS
The Insomnia Severity Index (ISI) was used to determine the presence of clinical insomnia (ISI score ≥ 15). Patient demographics, pain-related factors, and rash severity and location were evaluated with logistic regression analysis to identify risk factors of clinical insomnia among patients with PHN.


RESULTS
In total, 50.5% of patients reported mild to severe insomnia symptoms (ISI score ≥ 8) after pain development. Moderate to severe clinical insomnia (ISI score ≥ 15) was observed in 30.6% of PHN patients. Multivariate logistic regression analyses revealed that high pain intensity was the strongest predictor of clinical insomnia (odds ratio (OR) = 12.417, 95% confidence interval (CI): 2.990-51.561, P = 0.001). However, presence of mechanical allodynia (OR = 4.263, 95% CI: 1.040-17.481, P = 0.034) and high anxiety and depression level (OR = 4.452, 95% CI: 1.201-16.508, P = 0.026; OR = 6.975, 95% CI: 1.425-34.138, P = 0.017) were also significantly associated with clinical insomnia after adjusting for pain score. Clinical insomnia was not significantly related to age, gender, rash severity, or location of skin lesion.


CONCLUSIONS
Insomnia should be addressed as an important part of pain management in PHN patients with these risk factors, especially in patients with severe pain.