Modifiable Risk Factors and the Development of Psoriatic Arthritis in People With Psoriasis

A. Green; G. Shaddick; R. Charlton; J. Snowball; A. Nightingale; C. Smith; W. Tillett; N. McHugh

Disclosures

The British Journal of Dermatology. 2020;182(3):714-720. 

In This Article

Abstract and Introduction

Abstract

Background: Psoriatic arthritis (PsA) is a progressive and often destructive joint disease affecting approximately 20% of people with psoriasis.

Objectives: To investigate associations between obesity, changes in body mass index (BMI), alcohol intake and smoking status and the development of PsA in people with psoriasis.

Methods: We undertook a cohort study involving incident cases of psoriasis identified from the U.K. Clinical Practice Research Datalink between 1998 and 2014. The associations between smoking, alcohol and BMI and development of PsA were assessed using generalized additive models. Additionally, the risks associated with a change in BMI during follow-up were investigated using distributed lag nonlinear models.

Results: We identified 90 189 incident cases of psoriasis (42% male, mean age 51 years), of whom 1409 had a subsequent record of PsA diagnosis. BMIs of 25·0–29·9, 30·0–34·9 and ≥ 35·0 kg m−2 were significantly associated with an increased risk of developing PsA compared with BMIs < 25·0 kg m−2: adjusted odds ratios (95% confidence intervals) 1·79 (1·46–2·19), 2·10 (1·67–2·63) and 2·68 (2·09–3·43), respectively. Reducing BMI over a 10-year period (linearly) was associated with a reduction in the risk of developing PsA compared with BMI remaining constant over the same period. Increased risks of developing PsA were associated with moderate drinking but not with former or heavy drinking or with current or past smoking status.

Conclusions: In this incident psoriasis cohort, increased BMI and moderate drinking, but not heavy drinking or smoking status, were associated with an increased risk of PsA in people with psoriasis. Importantly, we have shown that reducing weight may result in a reduction in the risk of developing PsA.

Introduction

Psoriatic arthritis (PsA) is a progressive and often destructive joint disease affecting approximately 20% of people with psoriasis.[1] PsA causes pain, swelling and joint stiffness and is accompanied by chronic disfiguring skin disease; it can lead to impaired quality of life.[2] For the majority of people with psoriasis, PsA is diagnosed after, or synchronously with, the onset of psoriasis,[3] identifying them as a target group for investigating modifiable risk factors in the development of PsA.

While the association between obesity and an increased risk of psoriasis is well documented,[4] fewer studies have investigated its association with the risk of developing PsA. Three studies have found an increased risk of PsA among obese people with psoriasis, with the risk increasing with increasing body mass index (BMI).[5–7] However, these studies have only considered the effect of obesity as a single exposure, whereas the effect of obesity on the risk of developing PsA in people with psoriasis may occur with some delay and may change over time.

The role of smoking in the development of PsA is less clear, with studies reporting conflicting results.[8–11] The conflicting results may relate to different study designs and timing of smoking measurement. While there is substantial evidence suggesting that alcohol intake is associated with risk of psoriasis, the relationship between alcohol intake and risk of PsA is less established.[12–17] Two studies have found an increase in alcohol consumption to be associated with an increase in the risk of developing PsA.[14,15] Additional studies are therefore needed to determine better the role of smoking and alcohol in the development of PsA.

The aim of this study was to examine the associations between obesity, changes in BMI, alcohol consumption and smoking status, and the development of PsA in people with psoriasis, using data from the Clinical Practice Research Datalink (CPRD). Understanding these modifiable risk factors is essential in determining those who are at greatest risk of developing PsA, and hence will inform clinical recommendations on potential lifestyle adjustments that may reduce that risk.

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