Rosacea may increase risk for glioma, according to a nationwide cohort study in Denmark.

The findings, published online in JAMA Dermatology,  suggest that an increased focus on neurologic symptoms in patients with rosacea may be warranted.

Exactly how the two conditions are linked is not fully undersood. “This association may be mediated, in part, by mechanisms dependent on matrix metalloproteinases,” study authors write. Rosacea has a poorly understood pathogenesis in which increased matrix metalloproteinase activity might play an important role. Glioma accounts for 80 percent of all primary malignant tumors in the central nervous system, and these tumors also show upregulation of certain matrix metalloproteinases, they note.

All Danish citizens 18 years or older from January 1, 1997, to December 31, 2011, were eligible for inclusion in the cohort study. A total of 5,484, 910 individuals were eligible for analysis; of these, 68,372 had rosacea and 5,416,538 constituted the reference population. Data were analyzed from July 14 to August 10, 2015. Of the 5,484,910 individuals in the study population, 21,118 individuals developed glioma during the study period, including 20, 934 of the 5, 416, 538 individuals in the reference population (50.4 percent women; mean [SD] age, 40.8 [19.7] years) and 184 of the 68 372 patients with rosacea (67.3 percent women; mean [SD] age, 42.2 [16.5] years).The incidence rate (95% CI) of glioma was 3.34 (3.30-3.39) in the reference population and 4.99 (4.32-5.76) in patients with rosacea. The adjusted incidence rate ratio (95% CI) of glioma in patients with rosacea was 1.36 (1.18-1.58) in our primary analysis. the adjusted incidence rate ratio was 1.82 (1.16-2.86) when analyses were limited to patients with a primary diagnosis of rosacea by a hospital dermatologist (n = 5,964), the study showed.