Study Solidifies Link Between Environment and Psoriasis Risk

Image Credit: © Ольга Тернавская - stock.adobe.com

Besides its initial impact, psoriasis is often associated with increased risks of comorbidities, particularly cardiovascular diseases.¹ While the exact causes of psoriasis are not fully understood, genetic and environmental factors are increasingly determined to play a role.

Research has highlighted the positive health impacts of green and blue spaces—areas with vegetation or water—on various health outcomes.² However, the link between these environmental factors and psoriasis remains largely unexplored. Some studies suggest that green spaces might be beneficial by reducing inflammation and affecting skin microbiota, which is notable when associated with psoriasis.³ The role of genetics in psoriasis has been reported to be significant, with polygenic risk scores (PRS) used to assess genetic predisposition.⁴ Environmental factors can also modify genetic risk, leading researchers behind a recent study to explore the link between residential environments and psoriasis.

The study uses UK Biobank data to examine how natural environments, domestic gardens, and green and blue spaces in specific buffer zones relate to psoriasis risk. Additionally, it investigated how genetic risk factors might influence these associations.⁵

“We observed significant associations of residential natural environments and green spaces with an increased psoriasis risk,” researchers stated. “Inversely, domestic gardens and blue spaces were negatively associated with the risk of psoriasis. Moreover, individuals with a high genetic predisposition who were simultaneously exposed to a high percentage of natural environments and green spaces had the greatest relative increase in psoriasis risk.”

Study Design and Methods

The study used data from the UK Biobank, a large ongoing study with over 500,000 participants recruited between 2006 and 2010.⁶ After excluding those with a history of psoriasis and missing covariate data, the final sample size for this study was 385,145 participants.Residential environments were assessed using land use data from 2005 (GLUD) and 2007 (Land Cover Map) for England. This data, applied to small geographic areas (LSOAs) with about 1500 residents each, categorized land use into various types including green and blue spaces. Proximity criteria were set at 300 meters (walking distance) and 1000 meters (neighborhood scale) from participants' homes.⁷ 

Results

Participants in the study had an average age of 56.5 years, with 54.3% being women. Over a median follow-up of 12.45 years, 3,755 new cases of psoriasis were identified out of 385,145 participants, resulting in an incidence rate of 71.63 per 100,000 person-years. Researchers stated patients with psoriasis tended to be older, men, white, smokers, alcohol drinkers, obese, and less physically active, and they lived in areas with fewer domestic gardens and blue spaces but more natural and green environments. The correlations between different types of residential environments showed that natural environments and green spaces were strongly positively correlated, while domestic gardens were negatively correlated with other types.

The study found that the associations between environmental exposures and psoriasis were stronger in younger individuals, men, and those in less deprived areas. In terms of joint effects, researchers observed that high exposure to natural environments combined with low exposure to domestic gardens increased psoriasis risk, as did high exposure to green spaces combined with low exposure to blue spaces.

Participants with high genetic risk for psoriasis (measured using PRS) had a higher risk of developing psoriasis when exposed to high levels of natural environments or green spaces. However, high exposure to blue spaces was associated with a lower risk in individuals with high genetic risk. Researchers found joint effects of high genetic risk and high exposure to natural or green spaces significantly increased psoriasis risk, while interactions between PRS and other environmental factors were less pronounced. An antagonistic interaction was noted between blue spaces and genetic risk.

Conclusion

This study, the first to explore the impact of residential environments on psoriasis risk within a large cohort, revealed that higher exposure to natural environments and green spaces increased psoriasis risk, while exposure to domestic gardens and blue spaces is associated with lower risk. Notably, individuals with high genetic predisposition to psoriasis exhibited the greatest risk when exposed to extensive natural environments and green spaces. Conversely, the study found exposure to blue spaces and domestic gardens had a protective effect, particularly within these high-risk genetic groups.

The study noted differences in these associations across various subgroups underscore the complex interplay between environmental exposure, genetic risk, and psoriasis development. Researchers behind the study suggested that future research should attempt to clarify the relationship between residential environments and psoriasis via other methodologies, such as animal studies, Mendelian randomization, or randomized clinical trials.

References

1. Rendon A, Schäkel K. Psoriasis pathogenesis and treatment. Int J Mol Sci. 2019 Mar 23;20(6):1475. doi: 10.3390/ijms20061475.
2. Potter JD, Brooks C, Donovan G, et al. A perspective on green, blue, and grey spaces, biodiversity, microbiota, and human health. Sci Total Environ. 2023;892:164772. doi:10.1016/j.scitotenv.2023.164772
3. Ribeiro AI, Tavares C, Guttentag A, Barros H. Association between neighbourhood green space and biological markers in school-aged children. findings from the Generation XXI birth cohort. Environ Int. 2019;132:105070. doi:10.1016/j.envint.2019.105070
4. Chen H, Poon A, Yeung C, et al. A genetic risk score combining ten psoriasis risk loci improves disease prediction. PLoS One. 2011;6(4):e19454. Published 2011 Apr 29. doi:10.1371/journal.pone.0019454
5. Chen L, Chen H, Mo L, et al. Spatial distribution of residential environment, genetic susceptibility, and psoriasis: a prospective cohort study. J Glob Health.2024;14:04139. Published 2024 Aug 6. doi:10.7189/jogh.14.04139
6. Sudlow C, Gallacher J, Allen N, et al. UK biobank: an open access resource for identifying the causes of a wide range of complex diseases of middle and old age. PLoS Med. 2015;12(3):e1001779. Published 2015 Mar 31. doi:10.1371/journal.pmed.1001779
7. Wheeler B. UK Biobank Project 15374 documentation of environmental indicators attributed to participants based on home location grid references. 2024. Accessed August 9, 2024. https://biobank.ndph.ox.ac.uk/showcase/ukb/docs/App15374Docs.pdf.