A study on the epidemiology of rosacea

Pharmacoepidemiology is the science of the use and the effects of drugs in large human populations. Although its original role was confined to post-marketing surveillance of rare or long-latency adverse drug events, the science is gaining increasing importance across different stages of drug development, where it has been applied to assess drug utilization patterns and cost-effectiveness, to characterize target populations of drugs in development, to evaluate undiscovered beneficial or detrimental drug effects, or to provide evidence of effectiveness when randomized controlled trials face ethical or practical barriers.
Rosacea is a common but under-investigated inflammatory skin disease, characterized by relapses and remissions. The exact pathomechanism of the skin disease remains to be elucidated, but recent findings indicate a key etiologic role of the innate immune system. Evidence-based treatment options for the skin disease are sparse and greatly needed.
The aim of the comprehensive rosacea project presented within this thesis was to contribute to the general understanding of the skin disease, thereby focusing on the impact of different drugs and diseases on incident rosacea. The project comprises six individual studies, set up in a case-control study design, using data from the General Practice Research Database (GPRD). This United Kingdom (UK)-based database contains longitudinal primary-care records of millions of patients, representative of the UK population. Information is recorded by general practitioners including demographics, lifestyle factors, medical diagnoses, referrals to secondary care, laboratory and diagnostic results, and a complete history of drug prescriptions.
The study population consisted of 53,927 patients with an incident rosacea diagnosis between 1995 and 2009 and the same number of rosacea-free controls, matched on age, sex, index date, general practice, and history in the database. Study 3.1 builds the basis of the project, and describes the study population in terms of demographics, lifestyle characteristics, and ocular symptoms. An overall incidence rate of diagnosed rosacea in the UK of 1.65 / 1,000 person-years was calculated, and stratified by age, gender, calendar time, and geographic region. While cigarette smoking seemed to prevent patients from developing rosacea, alcohol consumption yielded a marginal risk increase.
Studies 3.2 and Study 3.5 fathom the insufficiently supported notion regarding the association of rosacea with migraine (Study 3.2) and with psychiatric diseases (Study 3.5). Drug effects of triptans (Study 3.2) and of psychotropic drugs (Study 3.5) on incident rosacea were also studied. In contrast to previous findings, pre-existing migraine was not generally associated with incident rosacea, but post-menopausal women with severe migraine may be at a slightly increased risk of rosacea. Although mechanistically conceivable, triptans did not alter the risk of developing rosacea. Neither depression nor other affective disorders affected the relative risk of rosacea, but patients with diagnosed schizophrenia were diagnosed with rosacea less frequently. Although the latter finding is intriguing, it requires further investigation, as diagnostic bias cannot be ruled out. Of all psychotropic drugs, current lithium exposure may protect patients from developing the skin disease. Topical lithium has been proven to be effective in seborrheic dermatitis, and might be an interesting approach for rosacea therapy.
Two further studies evaluate the effect of diuretics (focus spironolactone, Study 3.3) and of other antihypertensive drugs (including β-blockers and calcium channel blockers, Study 3.6) on incident rosacea. In line with one previous study, spironolactone yielded a significantly decreased rosacea risk, whereas no other diuretic drug class showed an effect. Despite a generally assumed detrimental effect of calcium channel blockers on rosacea, Study 3.6 did not reveal an increased risk of rosacea for users of this drug class. β-blockers, which have been suggested as an off-label treatment for erythematotelangiectatic rosacea, revealed a small risk decrease, which is probably larger in erythematotelangiectatic rosacea patients alone. Especially with abundantly used therapeutics, such as antihypertensive drugs, sound evidence is required in order for healthcare professionals to make the right decisions in clinical practice.
Finally, Study 3.4 reports a previously uninvestigated decreased rosacea risk for patients with diabetes at an advanced disease stage, potentially due to impaired vasodilation. It remains to be clarified whether insulin enhances this effect.
In summary, these large population-based studies contribute to the understanding of rosacea yielding important evidence and raising new hypotheses. While some results may directly support clinicians in their daily decisions on rosacea treatment, yet others might spark follow-up projects on potential new treatment approaches for rosacea as well as on pathomechanistic aspects of the skin disease.