Is there a gender difference in the severity of psoriasis?

Psoriasis is a common skin condition with a prevalence of 2-4% in the Western world.

Whilst the prevalence increases more rapidly with age in young female patients (i.e., age <20 years) compared with young male patients, thereafter, the prevalence of psoriasis is similar in both sexes.

Whilst the prevalence of the disease is similar in males and females, it has long been assumed that the disease is less severe in women than in men. However, the evidence for this has been generally indirect, fragmented and inconclusive. Now a research team from Sweden have provided strong evidence in support of this thesis (ref 1).

This was a cross-sectional study based on the National Registry for Systemic Treatment of Psoriasis in Sweden (PsoReg), with 5438 patients experiencing moderate to severe psoriasis. Of the study subjects, 3252 (59.8%) were men and 2186 (40.2%) women and the prevalence of obesity was virtually identical for males (28.6%) and females (28.0%).

To measure the severity of disease at enrolment, researchers used the Psoriasis Area and Severity Index (PASI) score – widely regarded as the gold standard for assessing disease severity. PASI is a combined score consisting of several dimensions of psoriasis and is based on four body areas: head, trunk, arms and legs. For each area, three plaque characteristics are assessed according to the degree of erythema (redness), induration (thickness), and desquamation (scaling). The scores for each area are first summed and then converted to the final score, which ranged from 0 to a theoretical maximum of 72.

Analysis showed that women have less severe psoriasis compared with men, after controlling for several possible confounders, such as age, smoking habits etc. Importantly, this difference between sexes was true for all body areas, except the head, where the PASI scores were equal. The researchers speculate that this could be a consequence of sex- and gender-specific differences in hair growth, care, and styling, with women tending to protect the head from direct sunlight, thereby limiting the potential benefit of sunlight on psoriasis. This would tend to raise the PASI score for the head area, making it more in line with the male score.

Given that men appear to have a more severe disease than women, it is no surprise that several studies have confirmed that men are more likely to receive systemic treatments than women. One study from Ireland showed that twice as many men received systemic treatment compared with women and that women had less severe psoriasis compared with men (ref 2). In addition, European registries of systemic treatment for psoriasis show a large dominance for males: Denmark 66%, Germany 60%, Italy 67%, The Netherlands 68%, and Spain 63% (ref 3).

Key points

• This is the first study to confirm genders difference in the severity of psoriasis
• The overall prevalence of psoriasis is similar in both sexes
• The severity of psoriasis tends to be greater in men than women, for all body areas except the head

Men are more likely to undergo systemic treatment for their disease 

References

1. Hagg D, Sundstrom A, Eriksson M, Schmitt-Egenolf M. Severity of Psoriasis Differs Between Men and Women: A Study of the Clinical Outcome Measure Psoriasis Area and Severity Index (PASI) in 5438 Swedish Register Patients. Am J Clin Dermatol 2017; 18: 583–590
2. White D, O’Shea SJ, Rogers S. Do men have more severe psoriasis than women? 
   J Eur Acad Dermatol Venereol. 2012;2 6:126–7.
3. Ormerod AD, Augustin M, Baker C, et al. Challenges for synthesising data in a network of registries for systemic psoriasis therapies. Dermatology. 2012; 224:236–43.