US scientists who followed 78,000 women for 14 years found that having psoriasis, an immune system condition that appears on the skin in the form of thick, red scaly patches, was linked to a higher risk of developing diabetes and high blood pressure, and called for more research to find out if treating the complaint reduces the risk.

The study was the work of researchers from the Brigham and Women's Hospital, Harvard Medical School and Harvard School of Public Health, in Boston, Massachusetts and is published online in this month's issue of the Archives of Dermatology.

The prospective study included participants who were taking part in the Nurses' Health Study II, a cohort of over 116,000 women who were followed up from 1991 when they were aged between 27 and 44 years, to 2005. The women completed health questionnaires relevant to this study at baseline (when they enrolled), then every two years, and then in the final year of the study.

The researchers found over 78,000 of the participants in the overall cohort had completed a question about a lifetime history of doctor-diagnosed psoriasis in 2005, and only included in their analysis those who reported no history of diabetes or high blood pressure (hypertension) when they enrolled. They then looked for new diagnoses of diabetes or high blood pressure in the sample.

The results showed that:
  • 1,813 (2.3 per cent) of the 78.061 women who filled in the question about psoriasis reported having received a diagnosis of the complaint.

  • Over 14 years of follow up, 1,560 of the women (2 per cent) developed diabetes, and 15,724 (20 per cent) developed high blood pressure.

  • Compared with women without psoriasis, the women with psoriasis had a 63 per cent higher risk of developing diabetes (multivariate relative risk [MRR] 1.63, 95 per cent confidence interval [CI] ranged from 1.25 to 2.12).

  • Women with psoriasis also had a 17 per cent higher risk of developing high blood pressure (MRR 1.17, 95% CI 1.06-1.30).

  • Taking into account age, body mass index (BMI) and whether a woman smoked or not did not change the link between psoriasis and risk of diabetes or high blood pressure.
The authors concluded that:

"In this prospective analysis, psoriasis was independently associated with an increased risk of diabetes and hypertension."

They suggested more studies were needed to establish whether treating psoriasis might also reduce risk of developing diabetes or high blood pressure.

"Psoriasis and the Risk of Diabetes and Hypertension: A Prospective Study of US Female Nurses."
Abrar A. Qureshi; Hyon K. Choi; Arathi R. Setty; Gary C. Curhan.
Arch Dermatol. 2009;145(4):379 -382.
Published online April 2009.

Additional Sources: National Psoriasis Foundation.

Written by: Catharine Paddock, PhD