Why the link? Qureshi says it may be underlying inflammation, thought to play a role in all three diseases. His team will try to duplicate the study in men to see if the link holds.
Though previous studies have also found a link between the three diseases, Qureshi says they were studies that looked only at one point in time, while his study has a long follow-up period and many participants.
It's not known whether anti-inflammatory treatments can reduce the risk of getting the other diseases, he says. The research does suggest that psoriasis should be viewed as not just a skin disease, but as a systemic disorder, he says.
Qureshi's study was partially funded by the National Cancer Institute. He has served as a consultant and speaker for the drug companies Abbott, Amgen, and Genentech.
The new study adds to the credibility of the link between psoriasis and other disorders, according to William H. Eaglstein, MD, emeritus chair of the department of dermatology and cutaneous surgery in the Miller School of Medicine at the University of Miami. Eaglstein wrote an editorial about the Qureshi study and other research.
The follow-up design was important to find the link, he tells WebMD, as was the large sample size. "The size was probably needed to make the connection," he says.
Whether the link is due to inflammation alone or something else combined with the inflammation is not known, says Eaglstein, who is also vice president of global medical science for Stiefel Laboratories Inc., a pharmaceutical company that makes skin care products.
Until more is known about the link between psoriasis, diabetes, and blood pressure problems, he says, "The take-home message is that both patients and physicians should be alert to the possibility."