Abstract
Background
Chronic pruritus severely impacts the quality of life (QoL) of patients. Due to its multifactorial nature, the presence of factors that can predict itch-specific QoL needs comprehensive exploration.
Objective
To determine the sociodemographic and itch-related factors that predict itch-specific QoL among patients suffering from chronic pruritus.
Methods
We conducted a cross-sectional study on a cohort of patients with chronic pruritus at our itch clinic in Miami, Florida from 2016 to 2022 and explored predictors of itch-specific QoL using simple and multivariable linear regression models.
Results
Sociodemographic factors that had a negative impact on itch-specific QoL included female sex and multiracial ethnicity. The main itch-related factors that were associated with a negative impact on itch-specific QoL included pruritus in the upper extremity and buttocks/genital regions and associated factors such as pain, cold sensation, sweating, and stress.
Limitations
Single-center study at a tertiary care center with a primarily non-Hispanic White population and use of self-administered questionnaires.
Conclusions
A variety of factors help predict the itch-specific QoL in patients with chronic pruritus. Understanding these factors can help clinicians evaluate and treat patients suffering from chronic itch.
Key words: itch, pruritus, quality of life
Abbreviations used: CSU, chronic spontaneous urticaria; QoL, quality of life
Capsule Summary.
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Chronic pruritus can have a significant impact on quality of life.
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We found that the main predictors of poor quality of life in patients with chronic pruritus include female sex, multiracial ethnicity, itch location (upper extremity, buttocks), stress, and somatosensory sensations including pain, cold, and sweat.
Introduction
Chronic pruritus—defined as an itch lasting longer than 6 weeks—is a relatively common problem, with studies finding a lifetime prevalence of 22% and 25.5% in the general population.1,2 It is associated with a variety of diseases, including dermatologic, psychiatric, neurogenic, and systemic conditions. Several studies have explored how pruritus affects patients’ quality of life (QoL). Patients with chronic pruritus due to dermatologic conditions such as psoriasis and atopic dermatitis have reported more anxiety, depression, agitation, difficulty concentrating, and decrease in sexual desire and function.3, 4, 5, 6 The detrimental effect of pruritus on QoL is evident.
Due to its multifactorial nature, however, the role that certain factors play in predicting itch-specific QoL is less clear. Itch-related factors such as longer duration and higher frequency have been found to correlate with a greater negative impact on QoL.7 Demographic factors such as race, sex, and marital status have also been found to influence a person’s itch-specific QoL.7,8 We performed a cross-sectional study to further investigate the relationship between sociodemographic and itch-specific factors in predicting the itch-specific QoL among a cohort of patients suffering from chronic pruritus in the United States.
Methods
We conducted a cross-sectional study on a cohort of patients who attended an itch clinic in Miami, Florida, United States, from 2016 to 2022. We included male and female patients aged 18 years or above with itching for at least 6 weeks.
Exposures
We recorded sociodemographic factors, history, diagnosis, and character of itch (location, frequency, pattern, worsening factors, and associated symptoms) using a self-administered questionnaire. We included age (years), sex (male or female), ethnicity (Hispanic, non-Hispanic White, non-Hispanic Black, non-Hispanic Asian, and multiracial), marital status (single, married, and widowed/divorced/separated), diagnosis (atopic dermatitis, psoriasis, chronic urticaria, other inflammatory conditions [eg, prurigo nodularis, contact dermatitis], and other diagnoses [eg, neuropathic pruritus, psychogenic pruritus, pruritus secondary to systemic condition]), locations of itch (head and neck, upper limb, lower limb, groin and buttocks, and trunk), itch episode frequency (≥10/d, 5-10/d, 2-4/d, and ≤1/d), presence of itch day and night (yes or no), factors making the itch worse (stress, sweat, dry skin, contact with irritants, and allergens, foods, hot-water, salt-water, and acid-drinks), associated symptoms (rash, pain, sweating, heat, and cold sensations), and intensity of itching1, 2, 3, 4, 5, 6, 7, 8, 9, 10 as predictors.
Locations of itch were initially assessed in 16 anatomical sites (face, scalp, neck, shoulder, armpit, chest, abdomen, back, buttocks, groin, hand, forearm, arm, thigh, shin, and foot) but combined to form 5 logical sites as described above. A single patient may have itch in multiple locations, as well as multiple worsening and associated factors. Sex, locations of itch, worsening factors, associated factors, and presence of itch day and night were defined as binary categorical variables, while binary dummy variables (yes or no) were created for each category of ethnicity, marital status, and itch episode frequency. Age and intensity of itch were defined as continuous variables.
Outcomes
Itch-specific QoL was assessed using a 22 items Itch-specific quality of life questionnaire,7,9 and the 22 items were grouped into 3 domains: 6 in symptomatic impact, 7 in functional limitation, and 9 in emotional impact. Each response to questions (eg, “my skin hurts because of my itchy skin condition”) was graded using a five-point Likert scale from 1 (never) to 5 (always). Then sub-scores were calculated for each domain by summating the numerical values of the responses in the particular domain (symptomatic impact [6-30]; functional limitation [7-35]; emotional impact [8-40]), and the total score (21-105) was calculated by summating sub scores of the 3 domains. Then, the average scores were calculated for each sub-score and the total score by dividing the sub-scores and total score by the number of items in the particular domain and the total number of items in the questionnaire, respectively. Higher average values were representative of poor QoL.
Statistical analysis
We summarized the sample using descriptive statistics, means, and standard deviations for continuous variables, and frequencies and percentages for categorical variables. We explored the predictors of itch-specific QoL using simple and multivariable linear regression models. The average total score and sub-scores of each domain of the Itch-specific quality of life questionnaire were defined as QoL outcomes and the above-mentioned exposure variables were defined as predictors. Model 1 was a simple linear regression model (unadjusted) assessing the relationship between the individual predictor and QoL outcome. Model 2 was a multivariable linear regression model including all predictor variables into a single model. Model 3 was a multivariable linear regression model with backward deletion and variables were sequentially removed (starting with the variable with the weakest association with QoL) until only those with a P value <.1 remained in the model. We reported beta values and 95% CI. Collinearity was examined using the Variance Inflation Factor. The variability of multivariable linear regression model 3 was assessed using adjusted R2. We have reported the significant findings of the model 3 in the results.
Statistical analysis was conducted using IBM SPSS Statistics 25.0 (IBM).
Results
Summary statistics
There were 720 patients who attended the itch clinic from 2016 to 2022, and participants with incomplete data were excluded (n = 201). Thus, the final sample included 519 patients and survey completion response rate was 72.08%. Table I shows the descriptive statistics of the sample. The mean age was 58 ± 17 years and 59% were females. The majority were non-Hispanic Whites (62.2%). The mean intensity of itching was 7.76 ± 2.26. Most participants had itching for more than 10 episodes per day, and 44.9% had itch day and night. The upper limb (79.2%) was the most frequent site of itch, followed by the trunk (72.3%) and lower limb (68.2%). The most frequent symptom associated with itching was rash (51.8%), and dry skin was the most common factor making the itch worse (52.2%), followed up by stress (46.8%) and sweat (46.6%). The mean average scores of total itch-specific QoL, symptom, function, and emotion domains were 3.41 ± 0.92, 3.20 ± 0.95, 3.40 ± 1.08, and 3.56 ± 1.07, respectively.
Table I.
Summary statistics of the sample
| Variable | Frequency (%) (n = 519) |
|---|---|
| Age (years), mean (SD) | 57.85 (17.18) |
| Sex | |
| Male | 215 (41.4) |
| Female | 304 (58.6) |
| Ethnicity | |
| Non-Hispanic White | 323 (62.2) |
| Non-Hispanic Black | 60 (11.6) |
| Non-Hispanic Asian | 17 (3.3) |
| Hispanic | 100 (19.3) |
| Multiracial | 19 (3.7) |
| Marital status | |
| Single | 153 (29.5) |
| Married | 281 (54.1) |
| Widow/divorced/separated | 85 (16.4) |
| Diagnosis (yes) | |
| Atopic dermatitis | 89 (17.1) |
| Psoriasis | 30 (5.8) |
| Chronic urticaria | 23 (4.4) |
| Other inflammatory | 198 (38.2) |
| Other diagnoses | 179 (34.5) |
| Location of itch (yes) | |
| Head and neck | 332 (64.0) |
| Upper limb | 411 (79.2) |
| Lower limb | 354 (68.2) |
| Groin and buttocks | 266 (51.3) |
| Trunk | 375 (72.3) |
| Symptoms associated with itch (yes) | |
| Rash | 269 (51.8) |
| Pain in itching area | 212 (40.8) |
| Sweating | 87 (16.8) |
| Heat sensation | 185 (35.6) |
| Cold sensation | 28 (5.4) |
| Factors which make the itch worse (yes) | |
| Stress | 243 (46.8) |
| Sweat | 242 (46.6) |
| Dry skin | 271 (52.2) |
| Contact with irritants | 135 (26.0) |
| Contact with allergens | 73 (14.1) |
| Foods | 54 (10.4) |
| Hot water | 169 (32.6) |
| Salt water | 31 (6.0) |
| Acidic drinks | 33 (6.4) |
| Presence of itch day and night (yes) | 233 (44.9) |
| Frequency of itch | |
| 1≤ episode/day | 70 (13.5) |
| 2-4 episodes/day | 118 (22.7) |
| 5-10 episodes/day | 118 (22.7) |
| >10 episodes/day | 213 (41.0) |
| Intensity of itch (1-10), mean (SD) | 7.76 (2.26) |
| ItchyQoL scores (average; 1-5), mean (SD) | |
| Symptom sub score | 3.20 (0.95) |
| Function sub score | 3.40 (1.08) |
| Emotion sub score | 3.56 (1.07) |
| Total score | 3.41 (0.92) |
| ItchyQoL scores (sums), mean (SD) | |
| Symptom sub score (6-30) | 19.20 (5.71) |
| Function sub score (7-35) | 23.82 (7.57) |
| Emotion sub score (8-40) | 28.51 (8.59) |
| Total score (21-105) | 71.53 (19.27) |
QoL, Quality of life.
Predictors of itch-specific QoL
Table II shows the results of the multivariable linear regression model 3, which explained 48%, 44%, 42%, and 35% variability associated with total itch-specific QoL, symptom, function, and emotion sub-domains, respectively. The female sex was associated with poor total itch-specific QoL, including all sub-domain scores, compared to the male sex. However, aging was associated with good itch-specific QoL in the symptom sub-domain. Interestingly, multiracial patients had poor itch-specific QoL in the symptom subdomain compared to the other races.
Table II.
Associations of predictors with itch specific quality of life in the adults—Itch-specific quality of life questionnaire
| Variables | ItchyQoL—model 3 |
|||
|---|---|---|---|---|
| Total score |
Symptom score |
Function score |
Emotion score |
|
| Beta (95% CI) | Beta (95% CI) | Beta (95% CI) | Beta (95% CI) | |
| Age (per 1 y increase) | - | −0.01 (−0.01, −0.00) | - | −0.01 (−0.01, 0.00) |
| Sex | ||||
| Female (vs male) | 0.28 (0.16, 0.40) | 0.18 (0.04, 0.31) | 0.26 (0.11, 0.42) | 0.38 (0.22, 0.54) |
| Ethnicity | ||||
| Non-Hispanic White (vs other) | - | - | - | - |
| Non-Hispanic Black (vs other) | - | - | - | 0.24 (−0.01, 0.48) |
| Non-Hispanic Asian (vs other) | - | - | - | - |
| Hispanic (vs other) | - | 0.17 (−0.01, 0.33) | - | 0.22 (0.02, 0.41) |
| Multiracial (vs other) | - | 0.37 (0.03, 0.71) | - | - |
| Marital Status | ||||
| Single (vs other) | - | −0.15 (−0.30, 0.01) | - | - |
| Married (vs other) | - | - | - | - |
| Widow/divorced/separated (vs other) | - | - | - | - |
| Diagnosis | ||||
| Atopic dermatitis (vs other) | - | - | - | - |
| Psoriasis (vs other) | - | - | - | - |
| Chronic urticaria (vs other) | −0.29 (−0.57, −0.01) | −0.56 (−0.88, −0.26) | - | - |
| Other inflammatory (vs other) | - | - | - | - |
| Other diagnoses (vs other) | - | - | - | - |
| Location of itch | ||||
| Head and neck (yes vs no) | - | - | - | - |
| Upper limb (yes vs no) | 0.21 (0.06, 0.36) | 0.22 (0.06, 0.39) | 0.38 (0.18, 0.57) | - |
| Lower limb (yes vs no) | - | - | - | - |
| Groin and buttocks (yes vs no) | 0.25 (0.12, 0.37) | 0.15 (0.02, 0.29) | 0.27 (0.11, 0.43) | 0.34 (0.18, 0.50) |
| Trunk (yes vs no) | - | - | - | - |
| Symptoms associated with itch | ||||
| Rash (yes vs no) | 0.16 (0.04, 0.28) | 0.28 (0.15, 0.41) | - | - |
| Pain in itching area (yes vs no) | 0.26 (0.14, 0.38) | 0.50 (0.36, 0.63) | 0.23 (0.08, 0.39) | - |
| Sweating (yes vs no) | - | 0.22 (0.05, 0.40) | - | - |
| Heat sensation (yes vs no) | 0.12 (−0.00, 0.25) | - | 0.14 (−0.02, 0.30) | - |
| Cold sensation (yes vs no) | 0.31 (0.05, 0.57) | 0.34 (0.05, 0.62) | - | 0.33 (−0.01, 0.66) |
| Factors which make the itch worse | ||||
| Stress (yes vs no) | 0.32 (0.20, 0.44) | 0.17 (0.04, 0.31) | 0.28 (0.12, 0.43) | 0.38 (0.22, 0.54) |
| Sweat (yes vs no) | - | - | 0.17 (0.01, 0.32) | - |
| Dry skin (yes vs no) | - | - | - | - |
| Contact with irritants (yes vs no) | - | - | 0.17 (−0.01, 0.34) | - |
| Contact with allergens (yes vs no) | - | - | - | - |
| Foods (yes vs no) | - | 0.20 (−0.02, 0.41) | - | - |
| Hot water (yes vs no) | - | 0.13 (−0.01, 0.27) | - | - |
| Salt water (yes vs no) | - | - | - | - |
| Acidic drinks (yes vs no) | - | - | - | - |
| Presence of itch day and night (yes vs no) | 0.30 (0.18, 0.43) | 0.12 (−0.02, 0.26) | 0.36 (0.20, 0.53) | 0.32 (0.16, 0.49) |
| Frequency of itch | ||||
| 1≤ episode/day (vs other) | −0.19 (−0.37, −0.01) | −0.25 (−0.44, −0.05) | - | −0.28 (−0.52, −0.05) |
| 2-4 episodes/day (vs other) | - | - | −0.19 (−0.38, −0.01) | - |
| 5-10 episodes/day (vs other) | - | - | - | - |
| >10 episodes/day (vs other) | - | - | - | - |
| Intensity of itch (1-10) (per 1 unit increase) | 0.13 (0.10, 0.16) | 0.10 (0.07, 0.14) | 0.14 (0.10, 0.17) | 0.14 (0.10, 0.18) |
Model 3 were constructed using multivariable linear regression with backward deletion and variables were sequentially removed (starting with the variable with the weakest association with QoL) until only those with a P value <.1 remained in the model.
Bold results are statically significant.
ItchyQoL, Itch-specific quality of life questionnaire; QoL, quality of life.
The site of pruritus, associated symptoms, and worsening factors of itching predicted poor itch-specific QoL. Itch in the upper limb was related to poor itch-specific QoL with respect to the total score, symptom, and function sub-scores, while itching in the groin and buttocks was associated with poor itch-specific QoL with respect to total and all sub-domain scores. Pain in the itching area was associated with poor total itch-specific QoL, including symptom and function sub-domain scores. Furthermore, having a rash in the itchy area and cold sensation were associated with poor total itch-specific QoL, including the symptom sub-domain score, while sweating was associated with poor itch-specific QoL in the symptom and function sub-domains only. Stress, as a worsening factor of itching, was associated with poor total itch-specific QoL, including sub-domain scores. Interestingly, patients with chronic urticaria diagnosis had good total itch-specific QoL, including symptom sub-domain score, compared to those with the rest of the diagnoses.
Increased intensity of itch predicted poor total itch-specific QoL, including all sub-domain scores. Similarly, the presence of itch day and night predicted poor itch-specific QoL with respect to the total score and function and emotion sub-domain scores. The lower frequency of itch predicted good itch-specific QoL compared to the higher frequency of itch.
Discussion
Pruritus characteristics/associated factors
We found that a variety of itch-related factors predicted a poor QoL. Similar to findings from previous studies, we concluded that higher intensity and higher frequency of itch were both associated with a worst QoL.7,10 Pain in the pruritic area was also found to be a predictor of poor QoL. The presence of pain may be due to the fact that peripheral and central sensitization in chronic itch involves similar neural mechanisms to those in chronic pain. In our observational study of 13,138 adults, we found that 53.3% of patients with skin conditions reporting pain had scores on a Dermatology Quality of Life Index that indicated low dermatology-related QoL.11 Both sweating and cold sensation all predicted a worse itch-related QoL in relation to at least 1 domain. In a study of patients with atopic dermatitis, 96% of patients reported that sweating increased the severity of their pruritus.6 For decades, cold stimuli have been reported to reduce itch. This led to the use of cooling agents such as topical menthol as a treatment for pruritus. Interestingly, we recently reported that itch in psoriasis is highly associated with the menthol cold receptor transient receptor potential cation channel subfamily M (melastatin) member 8 (TRMP8) expression.12 Moreover, in human experimental models of itch induction, cold stimuli did not inhibit itch while noxious heat robustly inhibited itch. This suggests that cooling agents may not be suited for many patients with chronic itch.13
Itch-associated stress was found to be a predictor of poor QoL, including sub-scores on all domains. Stress is known to exacerbate disorders such as atopic dermatitis and psoriasis, which could lead to a vicious cycle in patients experiencing stress from their pruritus. This is an important factor to consider when choosing treatment options for patients with pruritic conditions, for psychological treatment modalities could help reduce stress and thus improve patients’ QoL. Relaxation trainings such as progressive muscle relaxation and autogenic training have been shown to be helpful in treating patients with chronic itch, especially those with stress as an associated factor.14
The location of cutaneous lesions has been found to be a predictor of QoL in patients with other dermatologic conditions such as cutaneous lupus erythematosus and nonmelanoma skin cancers.15,16 Regarding location of pruritus, poorer QoL was associated with pruritus in the upper limb and groin/buttocks. Pruritus in the groin/buttocks area could be associated with itch in the genital region, which is known to significantly impact QoL. Studies evaluating patients with genital psoriasis have shown that they experience a more severe impairment in QoL than those without genital involvement, including impaired sexual functioning, fear of sexual relations, and decreased sexual desire.17,18 Many studies have found that nighttime pruritus negatively affects patients’ QoL, mostly because of the association with sleep disturbances.19,20 Others have found no association between time of day when itch is worst and Itch-specific quality of life questionnaire scores.7 Our results showed that having itch during the day and at night was associated with worse QoL outcomes. This could in part be related to daytime scratching behaviors, which have been found to be associated with higher levels of perceived stigmatization.4
In relation to diagnoses, we discovered that chronic urticaria was a predictor for a better itch-specific QoL when compared to the other pruritic conditions evaluated. These results should be cautiously interpreted, as patients with chronic spontaneous urticaria (CSU) with high urticarial activity scores have been reported to suffer a significant impairment of their QoL.21 A possible explanation for the better QoL in the patients with CSU in comparison to other chronic itch conditions is that the majority of severe CSU cases are not seen by dermatologists, and thus our patient population included mainly CSU of moderate severity. In moderate cases, itch tends to fluctuate and is less severe and constant.
Patient characteristics
Sociodemographic factors were also examined in our study. Female sex was found to be associated with poor QoL outcomes. Although this supports findings from some previous studies, others have not found a significant association between female sex and itch-related QoL.7,8 One study showed that while women suffering from chronic pruritus deem factors such as reducing itching and burning sensations, wearing all types of clothing, and experiencing less nervousness/depression as significantly more important therapy goals, men deemed contact with other people and a normal sex life as more important.22 Increasing age was found to be a predictor of better itch-specific QoL in the symptom subdomain. This is in accordance with findings that older age correlates with a less adverse impact on QoL.7
Lastly, multiracial ethnicity was found to be a predictor of poor itch-specific QoL in the symptom subdomain compared to other races. Studies have shown that non-White races experience a worse itch-specific QoL when compared to White patients.7,23 Regarding symptomatic impact, Shaw et al reported that patients in the “other race” category reported more burning and stinging associated with their pruritus.23 These findings suggest that these patients could have more pain with their itch, which would explain a lower QoL. Overall, this highlights the need to address racial disparities when treating patients who suffer from chronic pruritus.
Limitations
Our single-center study was conducted at a tertiary care center where we mostly see patients with moderate to severe pruritic conditions. Therefore, our results may not adequately reflect the impact of factors related to milder forms of itch on patients’ QoL. We mainly included patients of non-Hispanic White ethnicity (62.3%), which reflects the primary patient population at our Itch Clinic. Therefore, our results may not be applicable to populations of different ethnicities, especially considering that Black patients are affected by pruritus at greater proportions than their White counterparts24 and therefore may experience factors associated with poor itch-specific QoL outcomes at higher percentages.
Another potential limitation of this study is that a self-administered questionnaire was used to gather most of our data. When using questionnaires, recall bias is always a potential factor that can affect patient’s answers to the questions and therefore alter results. Also, we could not infer the causality of the itch-specific QoL due to the cross-sectional nature of this study. Regarding statistical analysis, we included many predictors into our multivariable regression models, including sociodemographic factors, characteristics of itch, associated symptoms, and worsening factors. However, we could not exclude residual confounding.
Conclusion
We identified a variety of predictive factors that affect QoL in a large cohort of patients suffering from chronic itch. Our results highlight important considerations that should be taken into account when evaluating patients presenting with chronic pruritus. Assessing for factors such as itch location, presence of pain with itch, and stress levels may enable dermatologists to better tailor treatment options that can address these factors and improve QoL in patients suffering from chronic itch. Further directions of research include assessing whether the integration of itch screening questionnaires as part of the clinical evaluation for patients with chronic pruritus could help with early detection of factors associated with a poor itch-specific QoL.
Conflicts of interest
Gil Yosipovitch reports were provided by University of Miami School of Medicine. Dr Yosipovitch is a consultant for Sanofi, Regeneron, Pfizer, Galderma, Novartis, Eli Lilly, Abbvie, Kiniksa, Trevi, Pierre Fabre, LEO, Escient, Celldex, and Bellus; is a board member for IFSI, NEA, NPF, and IEC; receives research support from Pfizer, Sanofi Regeneron, LEO, Eli Lilly, Kiniksa, Novartis, Escient, Bellus, Galderma, and Celldex. Choragudi and Soares have no conflicts of interest to declare.
Footnotes
Funding sources: None.
IRB approval status: University of Miami Institutional Review Board approved the study.
Patient consent: All the participants gave written informed consent for the study. I have read this consent form, which is printed in English (a language which I read and understand). This study has been explained to my satisfaction and all of my questions relating to procedures, risks and discomforts, and side effects have been answered. If I have any further questions regarding this study, or in the event of a study-related injury, I should contact the appropriate person named above. Based on this information, I volunteer to take part in this study.
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