Childhood disadvantage was linked to higher adult death rates in a review of 102 studies, 8.5 million people

Wealthier adults live longer than poorer ones. That gap is one of the most reliable patterns in public health, and most efforts to explain it look at adult life: jobs, smoking, access to a doctor. A harder question is how much of the gap was already in place by the time people left school.

Researchers at the University of Glasgow have now gathered nearly everything published on that question. Until now, they note, no recent meta-analysis has quantified these associations or graded how certain the evidence is. Their review, in The Lancet Public Health, covers 102 studies and about 8.5 million people. Adults who grew up in disadvantaged homes died at higher rates in the great majority of comparisons, across countries and whichever way disadvantage was measured. The authors also grade how far that evidence can be trusted, and the grade is mixed.

How much higher was adult mortality after a disadvantaged childhood?

Philip Broadbent, Vittal Katikireddi and their colleagues searched four research databases for studies that recorded something about a person’s circumstances in childhood and then followed them into adult life. The measures varied: a parent’s schooling or job, family income, the state of the housing. From 17,163 records they kept 102 studies, drawn from 24 countries.

The direction of the results was remarkably uniform. The authors report harmful associations in 390 of 474 estimates, or about four in every five. One pooled analysis of 18 studies turned that into absolute terms: 181 excess deaths per 100,000 people every year. At human scale, that is about one additional death a year among every 550 adults who grew up disadvantaged.

Money and parental schooling stood out among the measures. The team used a yardstick called the relative index of inequality, which compares people at the very bottom of a scale with those at the very top. For a household’s economic circumstances, mortality at the bottom was more than twice that at the top, and the figure for parental education was almost the same.

How sure can anyone be? Here the review is unusually direct. No randomized trial exists on the question, and all included studies were observational longitudinal studies, because nobody can assign children to poverty. Half of the studies were judged to be at high risk of bias, mostly for failing to account for other influences. On a standard four-step scale the certainty of the evidence ranged from very low to moderate. The estimate itself held steady when the weaker studies were dropped, and the authors describe their findings as consistent across exposure types, world regions, and risk of bias strata. A stable estimate resting on imperfect studies is the fair summary.

Which causes of death tracked childhood disadvantage?

Deaths from every cause rose together, but some rose more. The cause-specific analyses indicated elevated risks for cardiovascular death of about a quarter. For lung cancer the excess was about half, and for respiratory disease it was larger still, at 70% to 85% depending on sex.

That ordering is a clue. Lung cancer and chronic lung disease are driven heavily by smoking and by the air breathed at home and at work, and both follow poverty closely. The review does not test those pathways, so the pattern is suggestive and no more.

Is it childhood itself, or the adult life that follows?

A poor childhood often leads to a poor adulthood, and adult circumstances carry dangers of their own. A study of 1.7 million adults in The Lancet found that participants with low socioeconomic status had greater mortality compared with those with high socioeconomic status, a difference the authors put at about two years of life between ages 40 and 85. In the United States, tax records analyzed in JAMA showed the gap in life expectancy between the richest 1% and poorest 1% of individuals was 14.6 years for men.

Schooling, which is settled early in life, has its own measurable link. A global analysis by Norwegian and American researchers found that education showed a dose-response relationship with all-cause adult mortality, meaning the more years of schooling, the lower the death rate.

Epidemiologists have two broad ways of thinking about how early life gets under the skin, and an earlier review in this field set them out. In the critical period model, an exposure acting at a specific time has long-lasting effects on the structure or function of the body. In contrast, the accumulation of risk model suggests that effects accumulate over the life course, with each disadvantaged year adding to the last. The two are not rivals. Poor nutrition in infancy could do lasting harm on its own, while decades of worse housing and work pile further harm on top.

That earlier review, by Bruna Galobardes and colleagues at the University of Bristol in 2004, is also the measure of how far the field has come. It located 29 studies of childhood socioeconomic position and judged them too different to combine. Even so, eighteen of 22 studies found a higher risk of all-cause mortality associated with worse childhood socioeconomic circumstances. The Glasgow team had more than three times as many studies to work with and reached the same direction with numbers attached.

Weak controls in half the studies, and no experiments

The largest gap is one that more data will struggle to close. Since childhood circumstances are never assigned at random, any comparison can be distorted by things that travel with poverty, including parents’ health and the neighborhood. The authors rated 50 of the studies at high or very high risk of bias, primarily due to inadequate confounding control.

How childhood was measured is a further weakness of this literature. In the 2004 review, 10 of the 29 studies obtained data on childhood circumstances by participant recall during adulthood, which is less reliable than records made at the time. And a pooled figure for 24 countries hides how much the penalty may differ between, say, a Nordic welfare state and a country with little safety net.

For readers, nothing here is a personal forecast. An average across 8.5 million people says little about any one person, and plenty of those raised with little live long. What the review changes is the weight of the argument that early-life conditions matter for how long populations live. The authors conclude that disadvantaged childhood socioeconomic circumstances are associated with increased adult mortality across diverse measures of disadvantage and causes of death, and they call for early-life policies on that basis.

How much of that penalty comes from childhood itself, and how much from the adult life it leads to, is still unsettled.