The effect of statins on influenza-like illness morbidity and mortality.
The effect of statins on cytokine-mediated inflammatory responses may impact on the prognosis of influenza. We assessed whether statin use decreases the incidence of adverse influenza-related outcomes. Additionally, we used a new-user study design to minimize healthy user bias. We further examined the possibility of non-causal associations by using unrelated outcomes.



We used the UK Clinical Practice Research Datalink to identify all patients aged 30 or older diagnosed with influenza-like illness during 1997-2010. Statin users were compared with propensity score-matched patients not receiving statins. The outcome was hospitalization for influenza or pneumonia or death in the 30 days following influenza diagnosis. Logistic regression estimated cumulative incidence ratios.



The study cohort included 5181 statin users matched to 5181 non-users. The 30-day incidence of hospitalization or death was 3.5% in statin users and 5.2% in non-users, resulting in a 27% lower incidence with statin use (cumulative incidence ratio: 0.73, 95%CI: 0.59-0.89). New statin users were less protected against our composite outcome. The effect of statins was less pronounced among those with respiratory and cardiac disease. Statin use was shown to be associated with a non-statistically significant risk reduction of motor vehicle accident and burns.



The attenuation of the effect of statins with the new-user design, supporting evidence from the assessment of effect modification, and additional sub-analyses evaluating the effect of statins on non-related outcomes suggest that the beneficial effect of statins on influenza-related adverse outcomes may be explained by a healthy user bias. Copyright © 2016 John Wiley & Sons, Ltd.
Centre for Clinical Epidemiology, Lady Davis Research Institute, Jewish General Hospital, Montreal, Quebec, Canada.|Departments of Medicine and of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Quebec, Canada.
Paul
P
Brassard
Centre for Clinical Epidemiology, Lady Davis Research Institute, Jewish General Hospital, Montreal, Quebec, Canada.
Jennifer W
JW
Wu
Centre for Clinical Epidemiology, Lady Davis Research Institute, Jewish General Hospital, Montreal, Quebec, Canada.|Departments of Medicine and of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Quebec, Canada.
Pierre
P
Ernst
Centre for Clinical Epidemiology, Lady Davis Research Institute, Jewish General Hospital, Montreal, Quebec, Canada.
Sophie
S
Dell'Aniello
Centre for Clinical Epidemiology, Lady Davis Research Institute, Jewish General Hospital, Montreal, Quebec, Canada.
Brielan
B
Smiechowski
Centre for Clinical Epidemiology, Lady Davis Research Institute, Jewish General Hospital, Montreal, Quebec, Canada.|Departments of Medicine and of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Quebec, Canada.
Samy
S
Suissa
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D015331:Cohort Studies; D016207:Cytokines / Q000378:metabolism; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000008:administration & dosage*; D015994:Incidence; D007249:Inflammation / Q000188:drug therapy / Q000821:virology; D007251:Influenza, Human / Q000150:complications / Q000188:drug therapy* / Q000401:mortality; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D006113:United Kingdom
D016207:Cytokines; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors
epidemiology; healthy user bias; influenza; pharmacoepidemiology; pneumonia; preventive therapy; statins