A population-based cohort study of 1m Danish children shows that adversity in childhood increases the risk of premature death in early adulthood (16-36 years of age) more than fourfold.
Researchers from the faculty of health and medical sciences at the University of Copenhagen recorded social and stressful adversity* in childhood among 1m Danish children. “We divided the children into five groups depending on the degree of adversity experienced in childhood. The more stressful experiences they have experienced during childhood, the higher the mortality rate in early adulthood. For the most vulnerable children, the mortality rate is surprisingly 4.5 times higher”, says Professor Naja Hulvej Rod from the department of public health.
The higher mortality rate mainly manifests itself in suicide and accidents, but the study also shows a higher risk of dying from cancer in this group.
According to the researchers, the results of the study stress the critical importance of broad structural public-health initiatives to reduce stressful adversity in childhood. For example, prevention of childhood poverty and other adversity in childhood. With time, it may help reduce social inequality in health.
“It is striking to see such a strong connection between adversity in childhood and mortality in the Danish welfare state, which among other things aims to promote financial stability among families with young children and to minimise social adversity. From an international perspective, you may worry that these associations are even stronger in a less extensive welfare system”, says Rod.
The study is the first of its kind on a global basis. The size of the study has made it possible for the researchers to study the associations between incidents of social and stressful adversity throughout childhood and how it affects mortality rates among young adults.
*In the study, social adversity is defined as financial poverty or long-term unemployment in the family, while stressful adversity includes – death of a parent, divorce or alcohol/drug abuse among the parents.
Group 1: 54 % of the children experienced no or only very few isolated incidents of adversity in childhood.
Groups 2-4: 43 % of the children experienced isolated incidents of adversity in childhood, mainly related to poverty or illness in the family. Here the researchers found a mortality rate in early adulthood that is 1.3-1.8 times higher than in Group 1.
Group 5: 3 % experienced great social and stressful adversity throughout childhood. In this group, the mortality rate is 4.5 times higher than in Group 1.
Background: Childhood is a sensitive period with rapid brain development and physiological growth, and adverse events in childhood might interfere with these processes and have long-lasting effects on health. In this study, we aimed to describe trajectories of adverse childhood experiences and relate these to overall and cause-specific mortality in early adult life.
Methods: For this population-based cohort study, we used unselected annually updated data from Danish nationwide registers covering more than 1 million children born between 1980 and 1998. We distinguished between three different dimensions of childhood adversities: poverty and material deprivation, loss or threat of loss within the family, and aspects of family dynamics such as maternal separation. We used a group-based multi-trajectory clustering model to define the different trajectories of children aged between 0 and 16 years. We assessed the associations between these trajectories and mortality rates between 16 and 34 years of age using a Cox proportional hazards model and an Aalen hazards difference model.
Findings: Between Jan 1, 1980 and Dec 31, 2015, 2 223 927 children were included in the Danish Life Course cohort. We excluded 1 064 864 children born after 1998, 50 274 children who emigrated before their 16th birthday, and 11 161 children who died before their 16th birthday, resulting in a final sample of 1 097 628 children. We identified five distinct trajectories of childhood adversities. Compared with children with a low adversity trajectory, those who had early-life material deprivation (hazard ratio 1·38, 95% CI 1·27–1·51), persistent deprivation (1·77, 1·62–1·93), or loss or threat of loss (1·80, 1·61–2·00) had a moderately higher risk of premature mortality. A small proportion of children (36 081 [3%]) had multiple adversities within all dimensions and throughout the entire childhood. This group had a 4·54 times higher all-cause mortality risk (95% CI 4·07–5·06) than that of children with a low adversity trajectory, corresponding to 10·30 (95% CI 9·03–11·60) additional deaths per 10 000 person-years. Accidents, suicides, and cancer were the most common causes of death in this high adversity population.
Interpretation: Almost half of Danish children in our study experienced some degree of adversity, and this was associated with a moderately higher risk of mortality in adulthood. Among these, a small group of children had multiple adversities across social, health, and family-related dimensions. This group had a markedly higher mortality risk in early adulthood than that of other children, which requires public health attention.
Naja H Rod, Jessica Bengtsson, Esben Budtz-Jørgensen, Clara Clipet-Jensen, David Taylor-Robinson, Anne-Marie Nybo Andersen, Nadya Dich, Andreas Rieckmann
University of Copenhagen The Faculty of Health and Medical Sciences material
The Lancet abstract