Psoriasis Risk According to BMI: Q&A With Dr Amit Garg

Amit Garg, MD, is a professor and the founding chair for the department of dermatology at the Donald and Barbara Zucker School of Medicine at Hofstra University in Hempstead, NY. Dr Garg is a skilled medical dermatologist and educator. He is known for his outstanding expertise in autoimmune and inflammatory skin diseases including psoriasis and hidradenitis suppurativa. He shared his insights on the relation between psoriasis and body mass index (BMI) through the recent cohort analysis¹ he coauthored.

What was the reason you and your team conducted this study?
Obesity is associated with a proinflammatory state in which white adipose tissue secretes a similar profile of cytokines as with psoriasis, and this potentially links the two conditions.While the association between psoriasis and obesity has been described previously, data on this relationship in United States-based cohorts is mostly limited to the Nurses’ Health Studies, which include highly selected samples.Moreover, the temporal relationship between obesity and psoriasis has not been well established. So we did this study in order to evaluate the risk of developing psoriasis in patients with different BMI categories and to assess whether the association between psoriasis and obesity differs across patient subgroups.

Your study found that BMI “independently influences the development of psoriasis.” What is the significance of these findings?
In evaluating a demographically heterogeneous sample of over 1.5 million patients in the US, we noted that that incidence of psoriasis per 10,000 person-years was 9.5 among normal or underweight patients, 11.9 among overweight patients, 14.2 among obese class-1 patients, and 17.4 among obese-class two-thirds patients. Compared with patients with a BMI less than 25.0, those who were overweight, obese-class 1, and obese-class two-thirds had 1.2, 1.3 and 1.8 times the risk of developing psoriasis, respectively.

Can you share what areas of future research are needed to better understand the relationship between BMI and psoriasis?
The mechanistic links between obesity and psoriasis are not well established. The T_H1 and T_H17 pathways are implicated in both obesity and psoriasis, and there are likely other shared mechanism which are yet to be elucidated. Understanding the mechanism linking the two conditions may help us individualize treatment approaches for patients who are obese with psoriasis.

How should dermatologists work together with their patients to lower psoriasis development utilizing BMI?
Dermatologists can discuss obesity as a risk factor for developing psoriasis. However, it is not likely that obesity is the singular risk involved, and other risk factors, such as genetics, are not modifiable. It is also not yet clear that patients who are obese and at risk for developing psoriasis (ie, those with family history of psoriasis) can reduce this risk through weight management strategies. Dermatologists should take into consideration at least these two issues when counseling patients with psoriasis on obesity and weight management.

What clinical implications and considerations should dermatologists take from your study?
This analysis suggests that BMI independently influences the development of psoriasis. Higher BMI appears to be associated with increased risk of developing psoriasis independent of age, sex, race, and smoking status. Finally, there appears to be a graded association between BMI and risk of developing psoriasis.

Are there any tips or insights you’d like to share with your dermatologist colleagues regarding BMI or psoriasis?
The findings in this study should not further stigmatize patients with psoriasis. Given the negative impact of the condition on physical activity and psychosocial well-being, it is certainly likely that having psoriasis also contributes to weight gain in individual cases. There are also other risk factors that contribute to the development of psoriasis which we could not assess in this study. Indeed, there are numerous patients who are non-obese and also develop disease. Accordingly, it is essential that clinicians do not ascribe development of psoriasis to obesity alone.

Reference
1. Norden A, Rekhtman S, Strunk A, Garg A. Risk of psoriasis according to body mass index: a retrospective cohort analysis. J Am Acad Dermatol. Published online June 9, 2021. doi:10.1016/j.jaad.2021.06.012