Metformin Reduces Risk for Immune-Mediated Skin Diseases in Diabetes

Metformin is associated with a significantly lower risk for immune-mediated skin diseases, but not for androgen-mediated skin diseases among patients with type 2 diabetes, according to study results published in Dermatology.

Researchers sourced data from the National Health Insurance (NHI) database in Taiwan collected between 1999 and 2009. Patients who were treated with metformin in the initial 12-month period were assigned to the metformin group, and those who received antidiabetic medications other than metformin in the initial 12 month were assigned to the nonmetformin group.

The analysis included 360,506 patients (234,585 in the metformin group and 125,921 in the nonmetformin group). Intention-to-treat (ITT) and per-protocol (PP) analyses were performed, and follow-up continued until December 31, 2011.

Researchers used Cox regression with the inverse probability of treatment weighting and propensity score to estimate hazard ratios (HR) to compare skin diseases among those in the metformin group with those in the the nonmetformin group.

Metformin group participants were a mean age of 54.51 years, 59% were men, and the mean time since diabetes diagnosis was 1.65 years. Those in the nonmetformin group were a mean age of 56.5 years, 58% were men, and the mean time since diabetes diagnosis was 1.44 years.

Regarding the immune-mediated skin diseases (ie, urticaria, allergic contact dermatitis, and psoriasis), the HRs were 0.930 (95% CI, 0.920-0.940; P <.0001) in the ITT analysis and 0.930 (95% CI, 0.918-0.943; P <.0001) in the PP analysis.

Individually, the ITT analysis HR was 0.933 (95% CI, 0.918-0.948) for urticaria, 0.927 (95% CI, 0.916-0.938) for allergic contact dermatitis, and 0.898 (95% CI, 0.845-0.954) for psoriasis. The PP analysis HR was 0.910 (95% CI, 0.892-0.928) for urticaria, 0.899 (95% CI, 0.885-0.913) for allergic contact dermatitis, and 0.768 (95% CI, 0.714-0.826) for psoriasis.

Regarding androgen-mediated skin diseases (ie, acanthosis nigricans, hidradenitis suppurativa, and acne) in the ITT analysis, the HR was 1.110 (95% CI, 1.060-1.162; P < .0001), and in the PP analysis the HR was 0.990 (95% CI, 0.935-1.048; P = .7194).

Disease-specific HRs in the ITT analysis were 0.950 (95% CI, 0.633-1.425) for acanthosis nigricans, 1.028 (95% CI, 0.787-1.343) for hidradenitis suppurativa, and 1.116 (95% CI, 1.064-1.170) for acne. Disease-specific HRs in the PP analysis were 1.008 (95% CI, 0.623-1.633) for acanthosis nigricans, 1.033 (95% CI, 0.739-1.446) for hidradenitis suppurativa, and 0.988 (95% CI, 0.932-1.047) for acne.

Limitations of the study include possible disease misclassification and confounding by indication. Also, the analysis did not determine whether the use of a same set of confounders was adequate.

“Except for the need of a minor vigilance on the potential risk of acne, the multiple pleiotropic effects of metformin including a protection on immune-mediated skin diseases and skin cancer at the therapeutic doses required for hyperglycemic control provide supportive evidence for using metformin as the first-line antidiabetic drug, especially in patients who have potential dermatological problems,” conclude the study authors.