Prurigo Nodularis Tied to Greater Risk for Insomnia, Not Sleep Apnea and RLS

Prurigo nodularis is associated with the development of insomnia but not sleep apnea or restless leg syndrome (RLS), according to study findings published in JAAD International.

Patients with prurigo nodularis, a chronic inflammatory dermatosis, experience intensely itchy, severely pruritic nodules and papules on the limbs and trunk. Out of all dermatoses, patients with prurigo nodularis experience the lowest quality of life and low quality of sleep. Researchers conducted a retrospective cohort study to assess the association between prurigo nodularis and the development of sleep disorders. 

The researchers collected data from The Health Improvement Network (THIN), a database based in the United Kingdom with information on over 3 million patients. 

Participants with prurigo nodularis were identified and followed between January 1, 1994 and July 31, 2021. The primary outcome was the incidence of sleep disorders, including insomnia, RLS, and sleep apnea. The index date of prurigo nodularis was considered the date of diagnosis.

The researchers excluded patients with previous sleep disorders, including insomnia, sleep apnea, RLS, and narcolepsy, and patients with health care data of less than 1 year. 

A total of 4193 patients with prurigo nodularis and 4193 matched control group patients were identified from the database. The median age of participants was 57 years (standard deviation [SD], 19.4 years) and 57.4% were women. 

Of the patients with prurigo nodularis, 311 (7.4%) developed insomnia, 44 (1.0%) had

168 sleep apnea, 37 (0.88%) had RLS, and 374 (8.9%) had overall sleep disorder after the index date. Among the control group patients, 199 (4.7%) developed insomnia, 28 (0.67%) had sleep apnea, 25 (0.60%) had RLS, and 243 (5.8%) had overall sleep disorder after the index date.

After 1 year follow-up, it was reported that patients with prurigo nodularis had a significantly increased risk of developing overall sleep disorders (risk ratio [RR], 1.72; 95% CI, 1.16-2.54) and insomnia (RR, 1.75; 95% CI, 1.14-2.70). There was also an insignificant increased risk for sleep apnea (RR, 2.5; 95% CI, 0.49-12.88) and RLS (RR, 1.2; 95% CI, 0.37-3.93). This trend was also observed at 5-year follow-up. At 10 years follow-up, the RR for sleep apnea was found to be significant while RLS remained insignificant. 

The Cox regression models showed that prurigo nodularis was associated with insomnia (adjusted hazard ratio [aHR], 1.77; 95% CI, 1.48-2.12) and overall sleep disorder (aHR, 1.72; 95% CI, 1.46-2.02). However, the association between sleep apnea and RLS with prurigo nodularis were insignificant.

Some variables with a significant association to insomnia were major depressive disorder (aHR, 2.01; 95% CI, 1.33-3.06) and anxiety disorder (aHR, 1.62; 95% CI, 1.21-2.17).

One variable significantly associated with sleep apnea was obesity (aHR, 10.04; 95% CI, 4.28-23.5), and female sex was negatively associated with sleep apnea (aHR, 0.39; 95% CI, 0.24-0.64).

“Additional studies are needed to investigate interventions to optimize treatment of insomnia in PN [prurigo nodularis] patients,” the researchers wrote. “Dermatologists should be aware of this elevated risk for insomnia in PN patients for appropriate monitoring and referral for treatment.”

Study limitations are the potential underestimation of sleep and psychiatric disorders, confounding factors, and the lack of information on the treatment of prurigo nodularis and insomnia. 

Disclosure: One study author declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

This article originally appeared on Neurology Advisor