EMBARGOED UNTIL: Wednesday, September 11, 8:30 AM MDT
(Session 55, Paper B-388)
Oregon Publ. Hlth. Div., Portland, OR, United States
In addition to lowering cholesterol, there is some evidence that statins also have the ability to improve the body’s response to infection. For certain serious bacterial infections and influenza, some of the tissue damage and complications of the infection are caused by the body’s overactive immune response to the infection, and is not simply a direct result of the infection itself. In addition to preventing production of cholesterol, statins also have anti-inflammatory properties and can down-regulate the body’s inflammatory and immune response.
The current mainstays of influenza prevention and control strategies in the U.S., annual influenza vaccination and antiviral therapy in persons at high risk of complications, have their limitations. Vaccines can provide protection against influenza in otherwise healthy individuals but are less effective in the elderly, and circulating influenza strains may not always match the currently available vaccine. The neuraminidase inhibitor (NAI) class of antiviral medication reduces duration of symptoms by an average of one day when initiated within the first 48 hours of treatment but data suggesting that use of NAIs can prevent hospitalization are equivocal. Additionally, resistance to antiviral medications can develop. For these reasons, the potential role of statins in preventing severe illness and death from influenza has drawn much interest, particularly in the setting of a pandemic.
Reviewing the available literature on studies looking at use of statins in patients with influenza is a useful way to determine if there is enough evidence to recommend whether statins should be prescribed for patients with influenza. Three studies have investigated whether regular use of statins prevents influenza infection. Two were large studies conducted over several influenza seasons that looked at medical and pharmacy claims data over several years. The third asked travelers from France attending the Haj in Saudi Arabia before they left whether they were taking statins, and asked them about symptoms of influenza after their return. None of these studies found that statins were effective in preventing cases of influenza.
Another approach is to investigate patients diagnosed with influenza and determine whether those taking statins were less likely to have severe complications, such as death or admission to an intensive care unit. Two large studies, one in New Mexico and the other in Ontario, Canada, used pharmacy and medical claims data to look at this question and found a protective effect of statins in preventing hospitalizations and deaths from influenza. However, neither of these studies confirmed whether patients had influenza, so their conclusions should be taken with a grain of salt. Five additional studies used clinical data and studied only patients with laboratory-confirmed infection. A study of over 3,000 hospitalized patients during the winter of 2007-8 in the US found that, among patients with positive tests for influenza, those who had been taking statins were significantly less likely (41% less likely) to have died. A very similar study of patients hospitalized in the UK with influenza the following year, during the H1N1 pandemic, found similar results, although the results were not statistically significant. Three smaller studies, two from Mexico and one from Spain, reviewed the medical records of patients hospitalized with the H1N1 influenza virus in 2009; all three did not find a statistically significant protective effect of statins.
Observational studies such as the ones described above may be biased by lack of proper classification of statin use or laboratory confirmation of influenza; another source of bias, “healthy user” bias, may occur when persons found to be taking statins are actually healthier than those not taking statins, which would explain the protective effect of statins in some of the studies. In conclusion, the existing studies have found conflicting results and are not of high enough quality to suggest that patients diagnosed with influenza should be given statin medications. A randomized control trial would be the best type of study to determine whether a statins should have a role in the management of severe influenza.