Dermatology Online Journal

Sleep disturbances in psoriasis
Brandon G Shutty¹ DO, Cameron West¹ MD, Karen E Huang¹ MS, Erin Landis¹ AB, Tushar Dabade¹ MD, Betsy Browder¹ BS, Jenna O'Neill¹ MD, Megan A Kinney¹ MD MHAM, Ashley N Feneran¹ BS, Sarah Taylor¹ MD MPH DABFM, Brad Yentzer¹ MD, W Vaughn McCall² MD MS, Alan B Fleischer Jr¹ MD, Steven R Feldman^1,3,4 MD PhD
Dermatology Online Journal 19 (1): 1

1. Department of Dermatology
2. Department of Psychiatry
3. Department of Behavioral Medicine
3. Department of Pathology
4. Public Health Sciences
Center for Dermatology Research, Wake Forest University School of Medicine, Winston Salem, North Carolina

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Abstract

BACKGROUND: Psoriasis negatively impacts sleep, but the factors that cause this sleep disturbance are not well characterized. PURPOSE: To assess sleep quality in subjects with psoriasis. METHODS: 35 outpatients diagnosed with chronic plaque psoriasis affecting at least 10 percent BSA and 44 controls completed the Pittsburgh Sleep Quality Index, Patient Health Questionnaire, Itch Severity Scale, Insomnia Severity Index, and Epworth Sleepiness Scale. For multiple testing, alpha was set at 0.008. RESULTS: Adjusting for age, BMI, and gender, patients with psoriasis had 4.3 times the odds to score in a higher insomnia category (OR 95% CI: 1.7, 11.2; p=0.01), a trend toward experiencing "poor sleep" (p=0.04), and no difference in odds to be "sleepy" (p=0.83). Patients with psoriasis had greater itch than those without psoriasis (mean ISS 8.5 vs. 2.0; p<0.0001). When adjusting for age, BMI, gender, and depression, those with psoriasis were not more likely to experience poor sleep quality (p=0.25), nor to score in a higher insomnia category (p=0.20) or be more "sleepy" (p=0.53). CONCLUSIONS: Patients with psoriasis suffer from sleep disturbances and pruritus more than those without psoriasis. Although sleep disturbances are more prevalent, this may be secondary to depression rather than related to a direct effect of psoriasis.

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Introduction

Psoriasis is a physically, socially, and psychologically disabling disease [1-7]. Psoriasis impairs ability in everyday activities requiring use of hands, walking, sitting and standing for long periods of time, occupational performance, sexual activities, and sleep [4]. Sleep quality has been incorporated into several quality-of-life instruments used to assess the impact of psoriasis including the Psoriasis Disability Index, the Psoriasis Quality of Life Questionnaire, and the Psoriasis Index of Quality of life [1-6]. In a large mail survey conducted by the National Psoriasis Foundation in the United States, sleep was negatively affected in 22 percent of participants, independent of validated quality of life measures [4]. Similarly, a population-based study of atopic dermatitis in the United States found that one-third of participants experienced sleep disturbances [8]. Whereas psoriasis is known to generally impair sleep, the association between sleep disturbance and psoriasis has not been fully characterized.

Psoriasis may itch in a manner that impairs sleep [9, 10]. Pruritus, which is observed in 70 to 90 percent of psoriasis patients and commonly affects the trunk and extremities, is a daily, distressing symptom that parallels disease severity and negatively impacts quality of life [2, 3, 4, 6, 11-14]. Scratching occurs more frequently in sleep stages 1 and 2 than in slow wave sleep, precipitating nighttime arousals [9, 15].

Psoriasis is also associated with depression, which has also been shown to alter sleep [16, 17, 18]. Substance P plays a role in sleep disturbance and may be linked to the relationship between psoriasis, depression and sleep quality [19, 20]. The main purpose of this study was to measure prevalence of poor sleep quality in psoriasis subjects compared to age-, sex-, and BMI-matched subjects to better understand co-morbidities of the disease.

Methods

After institutional IRB approval, outpatients with chronic plaque psoriasis for at least 6 months as well as healthy controls recruited from the dermatology clinic completed questionnaires regarding their symptoms. Psoriasis patients were required to be over the age of 18 and have >10 percent BSA (body surface area) involvement for enrollment, as determined by a physician using the Psoriasis Area Severity Index (PASI). Surveys assessed the following:

1. Sleep Quality: The Pittsburgh Sleep Quality Index (PSQI) is a self-administered questionnaire that allows for subjective measure of sleep quality over the previous one month. Specifically, the questionnaire uses 4 open-ended questions and 14 questions based on a scale to assess subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, sleep-promoting medication use, and daytime dysfunction. The test is scored based on a 0-3 scale, in which “3” designates a negative outcome. A global sum of “5” or greater reflects poor sleep quality. PSQI has good reliability and validity.
2. Depression: The Patient Health Questionnaire (PHQ-9) is a self-administered questionnaire that correlates directly with the DSM-IV criteria for depression and is a standard instrument used for diagnosis. Because depression is a potential confounder known to impair sleep, the PHQ-9 was included in this study’s survey. The questionnaire includes 9 questions with a scale from 0-3, relating to the frequency of depressive symptoms with “3” being “nearly everyday.” Data analysis was carried out, both inclusive and non-inclusive of questions in the PHQ-9 concerning sleep, in order to observe relationships excluding depression’s known effects on sleep (falling asleep, staying asleep, or sleeping excessively).
3. Pruritus: The Itch Severity Scale (ISS) is a self-reported instrument that measures pruritus severity. It consists of 7 items related to itch description, frequency, and intensity and its effect on sleep, mood, sexual desire and function using a Likert scale and involved body surface area. Total ISS scores range from 0-21.
4. Insomnia: The Insomnia Severity Index (ISI) is a self-administered validated screening instrument for insomnia as well as a tool used in treatment research. Correlating with the DSM-IV criteria for Insomnia, the ISI measures symptom severity, distress, and daytime impairment using a 7 item survey. Total ISI score ranges from 0-28.
5. Hypersomnia: The Epworth Sleepiness Scale (ESS) is a self-administered questionnaire used to evaluate daytime somnolence; it is validated in obstructive sleep apnea. The ESS is an 8-item scale assessing severity of sleepiness while performing specified activities. Total scores on the ESS range from 0 to 24.

Statistics

To assess the relationship between psoriasis and the categorized levels of PSQI, ESS, ISI, and PHQ, frequencies and percentages were calculated and statistical significance was assessed using chi square and Fisher exact tests. Multivariable logistic regression was used to assess these relationships adjusting for gender, BMI, and age. Additional logistic regression models assessing the relationship between psoriasis and the sleep measures were also adjusted for depression using PHQ9. For the relationship between psoriasis and the continuous measures of PASI, ESS, PHQ9, ISS, ISI, and Global PSQI, means and standard deviations were calculated and statistical significance was assessed using t-tests and Wilcoxon rank sum tests. General linear modeling was used to estimate whether there was an association between psoriasis and the continuous measures of sleep after adjusting for gender, BMI, age, and/or depression (using PHQ9). To account for multiple comparisons for the five questionnaires and PASI measurement, a Bonferroni correction was applied so that the significance level was 0.008 for all logistic models and general linear models. Complete-case analyses were used for modeling. All analyses were performed using SAS 9.2 (Cary, NC).

Results

The majority of the subjects were male (58.2%, n=46) with a mean age of 44.2 years (± 14.6; range 18 to 74 years) and mean BMI of 29.6 kg/m² (± 7.1; range 18.1 to 59.8). Only one, two and three subjects did not complete the ISS, global PSQI and ISI questionnaires, respectively.

The mean ISS, an assessment of pruritus, was 4.8 (± 4.4; range 0 to 17.8). The mean global PSQI for sleep quality was 7.4 (± 4.5; range 1 to 22). Mean daytime somnolence as assessed by the ESS was 6.2 (± 3.3; range 0-17). The mean insomnia severity (ISI) was 8.3 (± 6.8; range 0 to 28) and the mean PHQ-9 was 5.5 (± 5.7; range 0 to 23) (Table 1).

Of all subjects, 44.3 percent (n=35) had psoriasis, with a mean PASI score (0 to 72) of 6.7 (± 9.4; range 0 to 43). Global PSQI assessment determined that 81.8 percent (n=27) of those with psoriasis experienced poor sleep, whereas only 18.2 percent (n=6) of those with psoriasis experienced normal sleep (p=0.05). The mean PSQI score for psoriasis patients (8.8 ± 4.4) was higher than for patients without psoriasis (6.3 ± 4.4; p=0.008). ESS, assessing mean daytime somnolence, found that 88.6 percent (n=31) of psoriatic patients were not “sleepy” and 11.4 percent (n=4) endorsed daytime “sleepiness.” Mean ESS scores did not differ among patients with or without psoriasis (p=0.35). Whereas 31.3 percent (n=10) of psoriasis subjects experienced no insomnia, 9.4 percent (n=3) experienced severe clinical insomnia as specified by the scoring criteria for the ISI; the mean ISI score was statistically greater for psoriasis patients compared to healthy controls (p=0.002). Concerning depression (PHQ-9), it was determined that of psoriasis subjects, 28.6 percent (n=10) had moderate depression, 5.7 percent (n=2) had moderately severe depression, and 11.4 percent (n=4) had severe depression. Mean PSQI scores were greater in subjects with rather than without psoriasis (p=0.0003; Table 1).

Adjusting for age, BMI, and gender, patients with psoriasis had 4.3 times the odds to score in a higher insomnia category using ISI (OR 95% CI: 1.7, 11.2; p=0.01), 6.1 times the odds to be depressed when viewing PHQ-9 scores (OR 95% CI: 2.3, 16.2; p<0.001), no more likely to be “sleepy” using ESS (p=0.83), and a trend toward “poor sleep” according to the PSQI (p=0.04). After controlling for age, gender, and BMI, patients with psoriasis had mean itch severity scores of 8.4 (95% CI: 7.3, 9.5), whereas those without psoriasis averaged 2.1 (95% CI: 1.2, 3.0; p<0.0001). When adjusting for age, BMI, gender, and depression through exclusion of depression-related sleep abnormalities on the PHQ-9, those with psoriasis were not significantly more likely to experience poor sleep (p=0.25), score in a higher insomnia category (p=0.20), nor be more “sleepy” using ESS (p=0.53). When adjusted for depression in addition to age, gender, and BMI, mean itch severity scores (ISS) were 7.6 (95% CI: 6.6, 8.6) in those with psoriasis and 2.7 (95% CI: 1.9, 3.6) in those without psoriasis (p<0.0001; Table 2).

As compared to controls for age, BMI, and gender, the mean PASI, mean PHQ-9, mean ISS, and mean ISI were significantly higher in patients with psoriasis (all p<0.008; Table 3). When adjusting for age, BMI, gender, and depression (as measured by PHQ-9 score), only mean ISS was significantly higher in patients with psoriasis (p<0.008; Table 4).

Discussion

Subjects with psoriasis were significantly more likely to experience insomnia than subjects without psoriasis, after controlling for age, gender, and BMI. Conversely, after discounting questions in the PHQ-9 concerning sleep, those with psoriasis were no more likely to encounter some level of insomnia than normal patients after adjusting for age, gender, BMI, and depression- level. Psoriasis has in the past been associated with disordered sleep quality, but this disturbance may be in large part secondary to depression rather than other aspects of the disease process.

The correlation between sleep disturbance and depression is well established; sleep impairments such as early morning awakenings are common symptoms of depression and often asked about as a clinical screening tool [16, 17, 18]. Problems with mood are also strongly correlated with worsened sleep quality [20]. Additionally, psoriasis has an established association with psychiatric morbidity. Specifically, depression has been observed to occur at a higher rate in patients with psoriasis compared to general population controls [6, 19, 21-25]. Prevalence of depression in patients with psoriasis ranges between 10 and 58 percent, with variability based on sample populations and different assessment tools [22]. Nearly half of the subjects with psoriasis in the current study demonstrated moderate to severe depression symptoms based on the PHQ-9 survey (Figure 1). Those with psoriasis were more likely to suffer from depression and had greater positive screening, or PHQ-9, outcomes. Notably, the prevalence of depression is higher among patients with psoriasis as compared to those with other dermatologic diseases such as lichen planus, atopic dermatitis, and acne [21, 22, 26]. In psoriasis, psychological distress likely relates to a combination of physical and social factors. Fatigue, feelings of helplessness in alleviating disease symptoms, and lack of social support are prominent predictors of distress in these patients [27]. However, the relationship between depression and psoriasis has not been well elucidated in the past.

Depression in the psoriasis patient correlates with disease severity and is related to difficulties associated with psoriasis, including problems related to social interaction and frustration with treatment in addition to impaired quality of life [24, 28]. Interestingly, individuals with moderate and severe depression are at higher risk for developing psoriasis [29]. Additionally, depression and pruritus are directly correlated and treatment of depression reduces symptoms of pruritus in psoriasis patients [29]. Depression is postulated to modulate itch perception by amplifying the need to scratch [30]. In the current study, subjects with psoriasis had average itch severity scores of 8.4, whereas those without psoriasis had an average score of 2.1 (p<0.0001; Table 3). The trend was similar after adjusting for depression-associated sleep disturbances, implying pruritus is associated with poor sleep quality, though it may or may not be causative (Table 4). Although psoriatic patients experienced greater pruritus, no conclusion can be made regarding its direct effect on depression-mediated sleep disturbance because the ISS survey did not specify questions concerning depression.

The present study had several notable limitations. The relatively small sample size may limit its ability to study all associations between demographic or clinical characteristics of some aspects of pruritus and depression. Although subjects in the psoriasis sample had moderate to severe psoriasis, findings may not be generalizable to general and private practice because the sample was recruited from one academic dermatology center. Finally, because few of the surveys dealt with depression, it was impossible to directly attribute depression and sleep quality to the symptoms of pruritus or sleepiness.

In conclusion, this study suggests that patients with psoriasis are more likely to suffer from sleep disturbances, possibly secondary to symptoms of depression associated with the psoriatic disease state. This knowledge is important because psoriasis and sleep disorders are each strongly associated with cardiovascular disease and metabolic syndrome [31-35]. Sleep disturbances can cause significant quality of life impairment; understanding the source of disease comorbidities in psoriasis patients, including sleep problems and their link to cardiovascular disease, may help to improve daily living and future treatment of the disease. Symptoms of pruritus and depression were frequently observed among the psoriasis sample, with depression independently compromising sleep. It may therefore be advisable to query patients about sleep quality because sleep disturbances may be indicative of depression, the treatment of which could improve patient outcomes and quality of life.

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