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

Abstract

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.