Cochrane systematic reviews of interventions for risk factors correlate weakly with global risk factor burden: a cross-sectional study.

BACKGROUND AND OBJECTIVES: Systematic reviews (SRs) are important for health-care decision-makers requiring evidence for interventions that target modifiable risk factors to prevent disease. We investigated whether Cochrane SR output correlated with risk factor burden as assessed by the Global Burden of Disease Study 2015. METHODS: We screened and extracted data from Cochrane reviews and protocols published since January 2011 investigating modifiable risk factors as outcomes. We calculated Spearman's rank correlation between number of occasions a risk factor was an SR outcome and that risk factor's global disease burden in disability-adjusted life years (DALYs). We also calculated standardized Pearson residuals (SPRs) of the variance between the observed and expected frequency of a risk factor featuring as an outcome. RESULTS: We obtained 400 unique SRs and 174 unique protocols from 6,392 Cochrane publications. Risk factors were an outcome a total of 965 times. The number of SR outcomes and DALYs per risk factor shared a weak-positive correlation (r = 0.45) for all risk factors, but was high (r = 0.83) for metabolic risks, similar for behavioral risks (r = 0.46), and weak negative for occupational and environmental risks (r = -0.40). SPRs for "high total cholesterol", "low bone mineral density", "alcohol and drug use" , and "child and maternal malnutrition" inferred a higher than expected frequency of outcomes, and for "air pollution", "dietary risk", and "unsafe water, sanitation, and hand-washing", fewer than expected. CONCLUSION: Our study investigated whether Cochrane risk factor SRs align with global risk factor burden, demonstrating a weak-positive correlation. Interventions modifying air pollution and dietary risks were sparsely studied, given disease burden.