Patients With Psoriasis May be at Greater Risk of Diabetic Retinopathy

Patients with diabetes and psoriasis are significantly more likely to develop new-onset, diabetes-related microvascular and macrovascular complications than are psoriasis-free patients with diabetes, according to the results of a large study which was presented to the annual congress of the European Academy of Dermatology and Venereology in Prague.

“In view of this greater likelihood of developing microvascular and macrovascular complications, clinicians may wish to consider closer disease management of diabetic patients with psoriasis,” said Dr. April W. Armstrong, director of clinical research and tele-dermatology for the department of dermatology at the University of California Davis Health System.

The study is the first to examine the impact of comorbid psoriasis and diabetes – two diseases characterized by systemic inflammation – on the risk of diabetic vascular complications.

She and her coinvestigators identified 6,164 adult patients with psoriasis and diabetes in the Thomson Reuters MarketScan medical records database. A limitation of the database is its lack of information regarding how well the participants’ diabetes was controlled, Dr. Armstrong noted.

The patients were matched to an equal number of control patients (psoriasis-free patients with diabetes) based on sex, diabetes type, prior diabetic complications, diabetic complications, and a vascular complications propensity score.

Then, the researchers analyzed the risk of incident diabetes-related microvascular and macrovascular complications over the subsequent 1, 3, and 5 years.

At 12 months’ follow-up, 18.3% of the patients with diabetes and psoriasis had developed new-onset diabetic microvascular complications – that is, retinopathy, neuropathy, or nephropathy – compared with 16.5% of controls. Similarly, 18.6% of patients with diabetes and psoriasis developed microvascular complications within this time frame, compared with 15.9% of controls.

Over the full 5 years of follow-up, 29.2% of the patients with diabetes and psoriasis experienced incident microvascular and 28.6% developed macrovascular complications, compared with 26.0% and 25.7% of control patients.

This translated to a highly significant adjusted 14% increased relative risk of incident microvascular complications in the cohort with comorbid diabetes and psoriasis, as well as a 13% increased incidence of macrovascular complications such as MI, heart failure, or stroke, Dr. Armstrong reported at the annual congress of the European Academy of Dermatology and Venereology.

At baseline, investigators classified 73% of the 6,164 psoriasis patients who also had diabetes as having mild psoriasis based on their use of topical therapies only, while the remaining 27% had moderate-to-severe psoriasis defined by their use of systemic medications or phototherapy.

Next, the researchers sought to find out whether the risk of diabetic vascular complications in patients with comorbid psoriasis climbed with increasing severity of their dermatologic disease. The answer turned out to be “sort of”, noted Dr. Armstrong.

That is, the adjusted 5-year risk of incident diabetic microvascular complications was 13% greater in patients with mild psoriasis than in psoriasis-free patients with diabetes, and 16% greater in those with moderate-to-severe psoriasis.

The results were consistent with the notion that more severe psoriasis, with its greater attendant systemic inflammation, spells greater vascular risk.

However, the risk for macrovascular complications wasn’t as clear cut. While the risk of diabetic macrovascular complications was increased 16% in patients with diabetes and mild psoriasis, the relative risk in those with moderate-to-severe psoriasis was only 10% more than in psoriasis-free patients with diabetes – and that degree of elevation didn’t achieve statistical significance.

One plausible explanation for this discordant finding, according to Dr. Armstrong, is that the use of systemic therapies in the cohort with moderate-to-severe psoriasis quelled their systemic inflammation, which dampened their risk for macrovascular disease to a level similar to that seen in patients with diabetes without psoriasis, which, it must be emphasized, is still significantly greater than in the general population without diabetes.

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