Is life expectancy really falling for groups of low socio-economic status? Lagged selection bias and artefactual trends in mortality

Abstract

Recent public health studies made headlines, 1-3 reporting that for some subpopulations in the USA, mortality rates have been higher and life expectancies lower for recent compared with earlier time periods. 4-7 These patterns have been described in both popular and academic discourse as a 'rise' in mortality or a 'decline' in life expectancy. We suggest that it is long past time to admit an alternative-and arguably more plausible-interpretation of these patterns. The fact that a measure was computed at two different time points does not, by itself, make the difference between them a trend. Imagine if researchers measured the average temperature for the whole of the USA a decade ago, and then for only Alaska this year, and found the former number to be lower than the latter. Would it be appropriate to say that average temperatures had 'declined' over the decade? We argue that it would not, and that it is likewise not appropriate to be describing many of the observed differences in subgroup life expectancy or mortality as 'trends'. Nevertheless, scholars and journalists alike have quickly adopted this 'trend' conclusion and given short shrift to an alternative interpretation that we find far more plausible. Here, we make the case that this alternative explanation should be the subject of serious empirical investigation and discussion in scholarly and public discourse, rather than getting the treatment it gets nowwhich is a cursory dismissal relegated to the 'limitations' sections of academic papers. We take seriously the reality of health disparities in the USA and the research and policy attention that they demand; understanding and redressing these disparities requires that trends be accurately characterized.

Complex health problems among the oldest old in Sweden: increased prevalence rates between 1992 and 2002 and stable rates thereafter

“…It is also possible that the relative importance of education for health varies over time. For example, as more recent cohorts have, on average, higher education, the selection into low education may be more strongly related to poor health (Mackenbach 2012;Dowd and Hamoudi 2014).…”

Increasing Disparities in Mortality by Socioeconomic Status

“…Meanwhile, the proportion with a college degree or more increased fourfold. Thus, it is possible that classifying individuals by completed grade or degree attained does not yield a consistent measure of SES rank across birth cohorts (4,14,22). This latter problem has received increased attention in recent years and can be addressed by converting to a relative as opposed to an absolute scale for years of schooling so that comparisons of mortality across birth cohorts focus on individuals at equivalent percentile points in the distribution for their own cohort.…”

Mortality Inequality: The Good News from a County-Level Approach

“…Examples of studies looking at inequality in mortality by education level include Pappas, Queen, Hadden, and Fisher (1993), Elo and Preston (1996), Preston and Elo (1995), Olshansky et al (2012), Meara, Richards, and Cutler (2008), Cutler et al (2011), Montez and Berkman (2014), and Montez and Zajacova (2013). The main difficulty with this approach is that the share of the population in different educational categories has changed dramatically over time (Dowd and Hamoudi 2014; Hendi 2015; Bound, Geronimus, Rodriguez, and Waidmann 2014; Goldring, Lang, and Shubik 2015). For example, the share of white, non-Hispanic women aged 25–84 who had less than a high school degree fell by remarkable 66 percent between 1990 and 2010.…”