Lifestyle changes for treating psoriasis

  • Protocol
  • Intervention



This is the protocol for a review and there is no abstract. The objectives are as follows:

To assess the effects of lifestyle changes for psoriasis.


Description of the condition

Psoriasis is a chronic inflammatory skin disease affecting about 2% of the population worldwide (Parisi 2013). Psoriasis most frequently presents with erythematous scaling plaques involving the scalp, trunk, and the extensor that is the outer side of the limbs (Treloar 2010). About 50% of people with psoriasis have nail involvement that may deform their nails (de Vries 2013). Psoriasis may also present with pustular lesions or with erythroderma that involves the entire skin (Mason 2013). Guttate psoriasis is a specific form that primarily occurs in children and young adults following a streptococcal sore throat or tonsillitis (Owen 2000). Psoriasis has a huge impact on quality of life, especially of people with skin lesions involving the hands and face (Yang 2015). Psoriasis causes a heavy economic burden on healthcare systems (Chi 2014).

Obesity has been associated with the development of psoriasis and psoriasis of increased severity (Debbaneh 2014). It has been proposed that the fat tissue acts like an endocrine organ and secretes proteins, such as adiponectin and leptin, which are involved in inflammation, altered glucose metabolism, and vascular endothelial biology (Gerdes 2011). Chronic inflammation is considered the link between psoriasis and associated co-morbidities, such as metabolic syndrome, cardiovascular disease, stroke, and renal diseases (Wang 2014; Chi 2015).

In addition to obesity, unhealthy lifestyles, such as excessive alcohol consumption, smoking, and a sedentary lifestyle, have been associated with onset and worsening of psoriasis (Gerdes 2010; Frankel 2012; Keyworth 2014). Stress (Naldi 2005; Altunay 2013) and lack of sleep (Treloar 2010) are also associated with worsening of psoriasis.

Description of the intervention

Psoriasis usually follows a relapsing-remitting course, but may evolve into persistent severe disease (Treloar 2010); there is no cure for psoriasis (Ryan 2014). The current available medical interventions include topical drugs (Mason 2013), phototherapy (Chen 2013), and systemic drugs (Wang 2014). The clinical decision for using these interventions either alone or in combination is made by physicians after considering the evidence for efficacy and safety, disease severity, and the person's preferences and circumstances (Chi 2013).

Psoriasis is associated with metabolic and cardiovascular co-morbidities that lifestyle changes, such as weight reduction, may modify (Chi 2015). The lifestyle change interventions that are potentially effective in treating psoriasis include diet, exercise, weight reduction, smoking cessation, and alcohol abstinence.

How the intervention might work

Adipose (fat) tissue in obese people with psoriasis produces inflammatory adipokines (bioactive products) and propagates inflammation, which plays a major role in both psoriasis and its associated co-morbidities (Gerdes 2011). The excessive adipose tissue in obesity may also increase the volume of drug distribution and diminish the response to medical treatments (Toussirot 2014). Two biological therapies, infliximab and ustekinumab, adopt weight-adjusted regimens to overcome the decrease in clinical response in obese people (Chi 2014). Weight reduction decreases the amounts of adipose tissue, and therefore could reduce inflammation and improve the severity of psoriasis and the response to medical treatments.

Lifestyle intervention Potential mechanism in treating psoriasis
Weight reduction

Reduction of the amounts of adipose tissue that causes inflammation

Decrease in the volume of drug distribution

Alcohol abstinenceReduction of inflammation associated with alcohol consumption
Smoking cessationReduction of the production of free radicals induced by smoking

Improvement of the body composition

Reduction of inflammation

Excessive alcohol consumption and smoking have been associated with psoriasis of increased severity (Gerdes 2010). Tumour necrosis factor-α (TNF-α) plays a major role in inflammation, which is a key feature in psoriasis (Serwin 2007). Excessive alcohol consumption increases the expression of TNF-α-converting enzyme (TACE) and plasma levels of tumour necrosis factor-α receptor (sTNF-α-R1) (Serwin 2008).

Smoking induces the production of free radicals that trigger inflammation and thus may promote the development of psoriasis (Armstrong 2014). Furthermore, smoking may increase the already increased risk of co-morbid cardiovascular disease in people with psoriasis (Armstrong 2014). Thus, alcohol abstinence and smoking cessation may help reduce inflammation and the severity of psoriasis (Treloar 2010).

Previous studies have found that exercise improves body composition (i.e. lowering of the percentage of body fat), reduces stress, and lessens chronic inflammation and the levels of pro-inflammatory cytokines (small proteins released by cells that promote inflammation) (Treloar 2010; Frankel 2012). Therefore, exercise may improve both the severity and co-morbidities of psoriasis (Treloar 2010).

Why it is important to do this review

Although there is a large body of evidence on the associations between unhealthy lifestyles and worsening of psoriasis, it is unclear if lifestyle changes can effectively reduce the severity of psoriasis or prolong the remission of psoriasis (Ryan 2014). We will conduct a systematic review to evaluate the evidence of the effects of lifestyle changes in treating psoriasis.


To assess the effects of lifestyle changes for psoriasis.


Criteria for considering studies for this review

Types of studies

Randomised controlled trials (RCTs) that assess the effects of lifestyle changes in treating psoriasis.

Types of participants

People with psoriasis diagnosed by a healthcare professional. We will not impose any limitations on the severity of psoriasis or the age of participants.

Types of interventions

We will include all lifestyle change interventions, including the following:

  • weight reduction;

  • alcohol abstinence;

  • smoking cessation;

  • dietary modification;

  • exercise; and

  • other lifestyle change interventions.

We will compare all of the listed lifestyle change interventions either alone or in combination against no lifestyle changes or another active intervention.

Types of outcome measures

Primary outcomes
  • Severity of psoriasis: the proportion of participants achieving at least 75% improvement from baseline in the Psoriasis Area and Severity Index (PASI 75). A European consensus proposed PASI 75 as a treatment goal for psoriasis (Mrowietz 2011). If PASI 75 is unavailable, we will use the proportion of participants achieving at least 50% or 90% improvement from baseline in PASI (i.e. PASI 50 and PASI 90, respectively). If none of these are available, we will use other validated assessment tools for psoriasis, including Body Surface Area (BSA), Physician Global Assessment (PGA), Lattice System Physician's Global Assessment (LS-PGA), Self-Administered Psoriasis Area Severity Index (SAPASI), Salford Psoriasis Index (SPI), Copenhagen Psoriasis Severity Index (CoPSI), and other validated assessment tools for psoriasis (Puzenat 2010).

  • Adherence to the intervention.

Secondary outcomes
  • Quality of life: as measured by validated tools, including Dermatology Life Quality Index (DLQI), 36-item Short Form (SF-36), Skindex 29, Skindex 17, Dermatology Quality of life Scale (DQOLS), Psoriasis Disability Index (PDI), Impact of Psoriasis Questionnaire (IPSO), Psoriasis Index of Quality of Life (PSORIQOL), and other validated quality of life assessment tools for psoriasis (Bronsard 2010). Regarding the DLQI, we will consider a DLQI score change of at least 5 as a minimally important difference (Khilji 2001).

  • Time to relapse.

  • Reduction in co-morbidities (e.g. reduction in obesity, hypertension, diabetes mellitus, and metabolic syndrome.

Search methods for identification of studies

We will include all relevant RCTs regardless of language or publication status (published, unpublished, in press, or in progress).

Electronic searches

We will search the following databases for relevant trials:

  • the Cochrane Skin Group's Specialised Registers;

  • the Cochrane Central Register of Controlled Trials (CENTRAL);

  • MEDLINE via Ovid (from 1946);

  • EMBASE via Ovid (from 1974);

  • LILACS (Latin American and Caribbean Health Science Information database; from 1982);

  • China National Knowledge Infrastructure (CKNI; from 1994); and

  • Airiti Library (publications and theses from Taiwan; from 1991).

We have devised a draft search strategy for RCTs for MEDLINE (Ovid), which is displayed in Appendix 1. We will use this as the basis for search strategies for the other databases listed.

Trials registers

We will search the following trials registers.

We have drafted a search strategy for the ISRCTN registry (Appendix 2), which we will modify for searching other trial registers.

Searching other resources

References from included trials

We will examine the reference lists of included RCTs to identify further references to relevant trials on lifestyle changes for treating psoriasis.

Unpublished literature

We will ask the authors of the included RCTs if they are aware of any relevant unpublished data.

Adverse effects

We will not perform a separate search for adverse effects of the lifestyle change interventions. We will only examine data on adverse events from the included RCTs.

Data collection and analysis

Some parts of this section uses text that was originally published in another Cochrane protocol (Chi 2012) and the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).

Selection of studies

Two review authors (CC and SK) will independently check the titles and abstracts from the searches. They will not be blinded to the names of the trialists and their institutions. If we can judge from the title and abstract that a study does not relate to an RCT on lifestyle change interventions for treating psoriasis, we will exclude it straight away. The same two review authors will independently examine the full text of each remaining study and judge if it meets our inclusion criteria. If the two review authors disagree on whether they should include a study, they will achieve unanimity through discussion with a third review author (MY). We will list the studies that we exclude after examining the full text and the reasons for exclusion in the 'Characteristics of excluded studies' tables.

Data extraction and management

Two review authors (CC and SK) will independently extract data from the included RCTs using a data extraction form. We will pilot test the data extraction form (Appendix 3). If there is disagreement about some data, the two review authors will consult with a third review author (MY) to achieve unanimity. One review author (CC) will enter the data into Review Manager 5 (RevMan 2014).

Assessment of risk of bias in included studies

We will use Cochrane's tool for assessing risk of bias in RCTs in evaluating the following domains (Higgins 2011).

  • Random sequence generation (selection bias): adequacy of the method of random sequence generation to produce comparable groups in every aspect except for the intervention.

  • Allocation concealment (selection bias): adequacy of the method used to conceal the allocation sequence to prevent anyone foreseeing the allocation sequence in advance of, or during, enrolment.

  • Blinding of participants and personnel (performance bias): adequacy of blinding participants and investigators from knowledge of which intervention a participant receives.

  • Blinding of outcome assessment (detection bias): adequacy of blinding outcome assessors from knowledge of which intervention a participant receives.

  • Incomplete outcome data (attrition bias): the completeness of outcome data for each main outcome, including attrition and exclusions from the analysis, whether attrition and exclusions are reported, the numbers in each intervention group (compared with total randomised participants), reasons for attrition or exclusions where reported, and any re-inclusions in our analyses.

  • Selective reporting (reporting bias). When the trial protocol is available, we will examine if all pre-specified outcomes are reported. When the study protocol is unavailable, we will examine if the published reports include all expected outcomes, including those that are pre-specified.

  • Other bias: any important concerns about bias not addressed in the other domains.

Two review authors (CC and SK) will independently assess the risk of bias of included RCTs. We will discuss with a third review author (MY) to resolve disagreements in assessment.

Measures of treatment effect

Dichotomous data

We will express dichotomous data as risk ratios (RR) with 95% confidence intervals (CI). When the RR is statistically significant, we will also present the number needed to treat for an additional beneficial outcome (NNTB) and number needed to treat for an additional harmful outcome (NNTH) with 95% CI and the baseline risk to which it applies.

Continuous data

We will express continuous data as difference in means (MD) with 95% CI. When different outcome scales are pooled, we will express continuous data as standardised mean differences (SMD) with 95% CI.

Time-to-event data

We will express time-to-event data as hazard ratios (HRs) with 95% CI.

Unit of analysis issues

We will not pool studies of different designs. For studies of the following types of design, we will analyse them separately using appropriate techniques described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).

Cluster-randomised trials

For cluster-randomised trials, we will employ the methods described in Chapter 16.3 in theCochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), and estimate the intervention effect assuming an intracluster correlation coefficient (ICC) of 0.072 (Adams 2004). We base this assumption on an analogy to a cluster RCT assessing the efficacy of adherence to the Adult Treatment Panel (ATP III) guidelines for cholesterol management (Parker 2005).

Cross-over trials

As carry-over effect of lifestyle changes cannot be excluded in cross-over trials, we will include only data from the first period for analysis.

Studies with multiple treatment groups

For studies with multiple intervention groups, we will make pair-wise comparisons of one intervention versus another.

Dealing with missing data

We will contact the trialists of studies less than 10 years old for missing data. When missing data are not available, we will conduct an intention-to-treat (ITT) analysis to recalculate the intervention effect estimates. That is, we will include all randomised participants in the analysis and assume those with missing dichotomous outcome data are treatment failures. For missing continuous outcome data, we will adopt the last observation carried forward (LOCF) approach in analysis.

Assessment of heterogeneity

We will assess the clinical diversity (i.e. variations in the participants, interventions, and outcomes) and methodological diversity (i.e. variations in the study design and risk of bias) to determine whether a meta-analysis is appropriate. We anticipate clinical heterogeneity will include baseline severity of psoriasis and various regimens of the same intervention.

We will calculate the I² statistic to assess statistical heterogeneity across the included trials. The Cochrane Handbook for Systematic Reviews of Interventions provides a rule of thumb as follows (Higgins 2011):

  • 0% to 40%: might not be important;

  • 30% to 60%: may represent moderate heterogeneity;

  • 50% to 90%: may represent substantial heterogeneity; and

  • 75% to 100%: considerable heterogeneity.

Assessment of reporting biases

When there are at least 10 trials that report useable data on primary outcomes for an intervention, we will use a funnel plot to examine the publication bias.

Data synthesis

We will provide a narrative description on all outcomes when data are available. We will only pool trials that are clinically homogeneous for participants, interventions, and outcomes. We will perform a meta-analysis employing the random-effects model to obtain a pooled intervention effect. When a meta-analysis is not feasible, we will summarise the data narratively instead. When relevant data are available, we will perform meta-regression to see whether amount of weight loss reduction is associated with an outcome.

Where results are estimated for individual studies with low numbers of outcomes (fewer than 10 in total) or where the total sample size is less than 30 participants and an RR is used, we will report the proportion of outcomes in each group together with a P value from a Fisher's exact test.

Subgroup analysis and investigation of heterogeneity

We will conduct the following subgroup analyses when adequate data are available.

  • Paediatric and adult participants.

  • Regarding lifestyle interventions that involve weight reduction, we will conduct a subgroup analysis on overweight and non-overweight participants.

Sensitivity analysis

We will conduct a sensitivity analysis to examine the intervention effects after excluding trials with high risk of bias for one or more key domains.

'Summary of findings' table

We will present at least one 'Summary of findings' table in our review summarising the main outcome data for the most important comparison (Higgins 2011), and will assess the quality of the body of evidence using the five GRADE considerations (study limitations, consistency of effect, imprecision, indirectness, and publication bias). When there are several major comparisons or the outcomes need to be summarised for different populations, we will produce more 'Summary of findings' tables.


We thank the Editorial Base of the Cochrane Skin Group for assistance in preparing this protocol.

The Cochrane Skin Group editorial base wishes to thank Robert Dellavalle, who was the Dermatology Editor for this protocol; Ben Carter, who was the Statistical Editor; Esther van Zuuren, who was Methods Editor; the clinical referee, Anawin Sanguankeo; and the consumer referee, Carolyn Hughes.


Appendix 1. Draft MEDLINE (Ovid) search strategy

  1. exp Psoriasis/ or psoria$.mp.

  2. palmoplantar$

  3. pustulosis palmaris et

  4. (pustulosis and palms and soles).mp.

  5. 1 or 2 or 3 or 4

  6. Diet/

  7. exp Dietary Supplements/

  8. exp food habits/ or meals/

  9. exp Diet Therapy/

  10. exp Nutrition Therapy/

  11. Caloric Restriction/

  12. Diet, Reducing/

  13. diet$.mp.

  14. Weight Reduction Programs/

  15. Weight Loss/

  16. (weight adj2 (loss or lost or reduc$ or eliminat$)).mp.

  17. ((body mass index or bmi) adj3 (reduc$ or decreas$ or low$)).mp.

  18. body mass index/

  19. Obesity/

  20. Overweight/

  21. exp Life Style/

  22. (lifestyle$ or life style$).mp.

  23. exp Health Behavior/

  24. (health and (behaviour$ or behavior$)).mp.

  25. Smoking Cessation/

  26. ((quit$ or stop) and smok$).mp.

  27. "Tobacco Use Cessation"/

  28. (smoking adj2 cessation).mp.

  29. Alcohol Abstinence/

  30. alcohol

  31. exp Alcohol Drinking/

  32. ((quit$ or stop) and (drinking or alcohol)).mp.

  33. exercis$.mp.

  34. exp Exercise/

  35. exp Exercise Therapy/

  36. Walking/ or sports/ or bicycling/ or running/ or swimming/

  37. Physical Fitness/

  38. (sport$ or walk$ or swim$ or cycl$3 or run$3 or jog$3).mp.

  39. (physical$ adj (fit$ or exer$ or activ$)).mp.

  40. Habits/

  41. risk reduction behavior/

  42. or/6-41

  43. randomized controlled

  44. controlled clinical

  45. randomized.ab.

  46. placebo.ab.

  47. clinical trials as

  48. randomly.ab.

  49. trial.ti.

  50. 43 or 44 or 45 or 46 or 47 or 48 or 49

  51. exp animals/ not

  52. 50 not 51

  53. 5 and 42 and 52

[Lines 43-52: Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE: sensitivity- and precision-maximising version (2008 revision)]

Appendix 2. Draft ISRCTN registry search strategy

  1. Condition: psoriasis AND Interventions: lifestyle

  2. Condition: psoriasis AND Interventions: diet

  3. Condition: psoriasis AND Interventions: weight reduction

  4. Condition: psoriasis AND Interventions: smoking cessation

  5. Condition: psoriasis AND Interventions: alcohol abstinence

  6. Condition: psoriasis AND Interventions: exercise

Appendix 3. Data extraction form

Study ID (first author, year of publication):


Funding source 

Risk of bias

Bias Authors' judgement Support for judgement
Random sequence generation (selection bias)  
Allocation concealment (selection bias)  

Blinding of participants and personnel (performance bias)

All outcomes


Blinding of outcome assessment (detection bias)

All outcomes


Incomplete outcome data (attrition bias)

All outcomes

Selective reporting (reporting bias)  
Other bias  

Contributions of authors

CC was the contact person with the editorial base; co-ordinated the contributions from the co-authors and wrote the final draft of the protocol; worked on the methods sections; drafted the clinical sections of the background and responded to the clinical comments of the referees; and responded to the methodology and statistics comments of the referees.
CC, SK, MY, SW, YT, and MH contributed to writing the protocol.
SW was the consumer co-author and checked the protocol for readability and clarity. She also ensured that the outcomes are relevant to consumers.
CC is the guarantor of the final review.


This project was supported by the National Institute for Health Research (NIHR), via Cochrane Infrastructure funding to the Cochrane Skin Group. The views and opinions expressed therein are those of the review authors and do not necessarily reflect those of the Systematic Reviews Programme, NIHR, National Health Service (NHS), or the Department of Health.

Declarations of interest

Ching-Chi Chi: nothing to declare.
Shu-Hua Ko: nothing to declare.
Mei-Ling Yeh: nothing to declare.
Shu-Hui Wang: nothing to declare.
Yu-Shiun Tsai: nothing to declare.
Mei-Ya Hsu: nothing to declare.

Sources of support

Internal sources

  • Chang Gung Memorial Hospital, Chiayi, Taiwan.

External sources

  • The National Institute for Health Research (NIHR), UK.

    The NIHR, UK, is the largest single funder of the Cochrane Skin Group.