Commentary: Chasing the elusive null—the story of income inequality and healthy

Backlund and colleagues,1 provide new multilevel evidence of a strong and robust association between US state income inequality and individual mortality in the <65-year-old adult population (relative risks of 1.39 for men and 1.13 for women, Table 2,1), even after conditioning this association on a range of covariates. Yet, this statistically and substantively significant finding is not a part of the study’s conclusion. Instead, the null association observed in the elderly population (565 years) is emphasized to conclude that ‘this explains why income inequality is not a major driver of mortality trends in the United States because most deaths occur at ages 65 and over.’ In this comment, we evaluate the substantive and empirical aspects of the study, which we believe helps to settle some disagreements in the field. The study, however, is also characteristic, somewhat unfortunately, of the way in whic