Mortality in Children Aged 0-9 Years: A Nationwide Cohort Study from Three Nordic Countries

Decreasing death rates and causes of death in Icelandic children-A longitudinal analysis

BACKGROUND

Global death rate in children has been declining during the last decades worldwide, especially in high income countries. This has been attributed to several factors, including improved prenatal and perinatal care, immunisations, infection management as well as progress in diagnosis and treatment of most diseases. However, there is certainly room for further progress. The aim of the current study was to describe the changes in death rates and causes of death in Iceland, a high-income country during almost half a century.

METHODS

The Causes of Death Register at The Directorate of Health was used to identify all children under the age of 18 years in Iceland that died during the study period from January 1st, 1971 until December 31st, 2018. Using Icelandic national identification numbers, individuals could be identified for further information. Hospital records, laboratory results and post-mortem diagnosis could be accessed if cause of death was unclear.

FINDINGS

Results showed a distinct decrease in death rates in children during the study period that was continuous over the whole period. This was established for almost all causes of death and in all age groups. This reduction was primarily attributed to a decrease in fatal accidents and fewer deaths due to infections, perinatal or congenital disease as well as malignancies, the reduction in death rates from other causes was less distinct. Childhood suicide rates remained constant.

INTERPRETATION

Our results are encouraging for further prevention of childhood deaths. In addition, our results emphasise the need to improve measures to detect and treat mental and behavioural disorders leading to childhood suicide.

Risk factors of post-discharge under-five mortality among Danish children 1997-2016: A register-based study

Objectives

Estimating associations between somatic and socioeconomic risk factors and post-discharge under-five mortality.

Design

Register-based national cohort study using multiple Cox regression.

Participants

The population of 1,263,795 Danish children live-born 1997–2016 who survived until date of first discharge to the home after birth was followed from that date until death, emigration, 5 years of age or 31 December 2016.

Main outcome measures

(A) Mortality hazard ratios (HRs) among all children, (B) mortality HRs among children without severe chronic disease, and (C) mortality HRs among children without severe chronic disease or asthma.

Main results

In the total population (1,947 deaths) severe chronic disease was associated with mortality HR = 15.28 (95% CI: 13.77–16.95). In children without severe chronic-disease (719 deaths) other somatic risk factors were immature birth HR = 3.40 (1.92–6.02), maternal smoking HR = 1.84 (1.55–2.18) and low birth weight HR = 1.74 (1.21–2.51). Socioeconomic risk factors for mortality included: maternal age < 25 years HR = 1.91 (1.38–2.64) compared to > 35 years (similar for 30–35 years and 25–29 years), lowest vs. highest family income tertile HR = 1.76 (1.23–2.51), not living with both parents HR = 1.63 (1.25–2.13), maternal unemployment HR = 1.54 (1.12–2.12), presence of siblings HR = 1.44 (1.20–1.71) and secondary vs. tertiary parental education HR = 1.33 (1.07–1.65) for fathers and HR = 1.23 (1.01–1.52) for mothers. Factors not found to be associated with child mortality in this population included presence of asthma HR = 1.29 (0.83–1.98) and non-Danish ethnicity HR = 0.98 (0.70–1.37).

Conclusions

Childhood death after discharge to the home after birth and before 5 years of age is a very rare event in Denmark. This ‘post-discharge’ mortality was heavily associated with severe chronic disease. In children without severe chronic disease, immature birth, maternal smoking and certain socioeconomic characteristics were noticeable risk factors. Mortality may possibly be decreased by focusing on vulnerable groups.

Too much? Mortality and health service utilisation among Danish children 1999-2016: A register-based study

OBJECTIVES

To describe the temporal development of mortality and health service utilisation defined as in- and outpatient hospital contacts, contacts with general practitioner and specialists, and prescribed dispensed medication among Danish children 0-5 years of age from 1999 to 2016.

DESIGN

Register-based descriptive study.

PARTICIPANTS

All children born in Denmark in the period 1994-2016 followed until 5 years of age.

MAIN OUTCOME MEASURES

Annual incidence rates of mortality and health service utilisation outcomes, and incidence rate ratios compared to the reference calendar year 1999. The new measure of post-discharge mortality is presented.

RESULTS

Post-discharge mortality decreased from 1999 to 2016, IRR2016 = 0.49 (95% CI: 0.36 to 0.66). Total contacts did not change much over time, IRR2016 = 1.02 (1.02 to 1.03), but increased among neonates, IRR2016 = 3.69 (3.63 to 3.75), and decreased among children with chronic disease IRR2016 = 0.94 (0.93 to 0.94). In- and out-patient hospitalisations increased, IRR2016 = 1.26 (1.24-1.27) resp. IRR2016 = 1.62 (1.60-1.63), contacts with medical specialists increased, IRR2016 = 1.43 (1.42 to 1.43), whilst contacts with general practitioner decreased, IRR2016 = 0.91 (0.91 to 0.91). Medication use decreased, IRR2016 = 0.82 (0.82 to 0.82).

CONCLUSIONS

Our measure of post-discharge mortality was halved during the study period indicating improved health. Overall health service utilisation did not change much, but the type of utilisation changed, and the development over time differed between subgroups defined by age and chronic disease status. Our findings call for considerations about the benefit of increased specialisation and increased use of health services among 'healthy' children not suffering from chronic disease.

Mediating roles of preterm birth and restricted fetal growth in the relationship between maternal education and infant mortality: A Danish population-based cohort study

BACKGROUND

Socioeconomic disparities in infant mortality have persisted for decades in high-income countries and may have become stronger in some populations. Therefore, new understandings of the mechanisms that underlie socioeconomic differences in infant deaths are essential for creating and implementing health initiatives to reduce these deaths. We aimed to explore whether and the extent to which preterm birth (PTB) and small for gestational age (SGA) at birth mediate the association between maternal education and infant mortality.

METHODS AND FINDINGS

We developed a population-based cohort study to include all 1,994,618 live singletons born in Denmark in 1981-2015. Infants were followed from birth until death, emigration, or the day before the first birthday, whichever came first. Maternal education at childbirth was categorized as low, medium, or high. An inverse probability weighting of marginal structural models was used to estimate the controlled direct effect (CDE) of maternal education on offspring infant mortality, further split into neonatal (0-27 days) and postneonatal (28-364 days) deaths, and portion eliminated (PE) by eliminating mediation by PTB and SGA. The proportion eliminated by eliminating mediation by PTB and SGA was reported if the mortality rate ratios (MRRs) of CDE and PE were in the same direction. The MRRs between maternal education and infant mortality were 1.63 (95% CI 1.48-1.80, P < 0.001) and 1.19 (95% CI 1.08-1.31, P < 0.001) for low and medium versus high education, respectively. The estimated proportions of these total associations eliminated by reducing PTB and SGA together were 55% (MRRPE = 1.27, 95% CI 1.15-1.40, P < 0.001) for low and 60% (MRRPE = 1.11, 95% CI 1.01-1.22, P = 0.037) for medium versus high education. The proportions eliminated by eliminating PTB and SGA separately were, respectively, 46% and 11% for low education (versus high education) and 48% and 13% for medium education (versus high education). PTB and SGA together contributed more to the association of maternal educational disparities with neonatal mortality (proportion eliminated: 75%-81%) than with postneonatal mortality (proportion eliminated: 21%-23%). Limitations of the study include the untestable assumption of no unmeasured confounders for the causal mediation analysis, and the limited generalizability of the findings to other countries with varying disparities in access and quality of perinatal healthcare.

CONCLUSIONS

PTB and SGA may play substantial roles in the relationship between low maternal education and infant mortality, especially for neonatal mortality. The mediating role of PTB appeared to be much stronger than that of SGA. Public health strategies aimed at reducing neonatal mortality in high-income countries may need to address socially related prenatal risk factors of PTB and impaired fetal growth. The substantial association of maternal education with postneonatal mortality not accounted for by PTB or SGA could reflect unaddressed educational disparities in infant care or other factors.

Childhood death rates declined in Sweden from 2000 to 2014 but deaths from external causes were not always investigated

AIM

Countries that conduct systematic child death reviews report a high proportion of modifiable characteristics among deaths from external causes, and this study examined the trends in Sweden.

METHODS

We analysed individual-level data on external, ill-defined and unknown causes from the Swedish cause of death register from 2000 to 2014, and mortality rates were estimated for children under the age of one and for those aged 1-14 and 15-17 years.

RESULTS

Child deaths from all causes were 7914, and 2006 (25%) were from external, ill-defined and unknown causes: 610 (30%) were infants, 692 (34%) were 1-14 and 704 (35%) were 15-17. The annual average was 134 cases (range 99-156) during the study period. Mortality rates from external, ill-defined and unknown causes in children under 18 fell 19%, from 7.4 to 6.0 per 100 000 population. A sizeable number of infant deaths (8.0%) were registered without a death certificate during the study period, but these counts were lower in children aged 1-14 (1.3%) and 15-17 (0.9%).

CONCLUSION

Childhood deaths showed a sustained decline from 2000 to 2014 in Sweden and a quarter were from external, ill-defined or unknown causes. Systematic, interagency death reviews could yield information that could prevent future deaths.

Association of Mortality With the Death of a Sibling in Childhood

IMPORTANCE

The death of a close relative is associated with an increased mortality risk among the bereaved, but much less is known about the potential association of the death of a sibling in childhood with mortality in this population.

OBJECTIVE

To examine the association between sibling death in childhood and subsequent mortality risk.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study of 5 005 029 participants evaluated linked national registers in Denmark (January 1, 1973, through December 31, 2009) and Sweden (January 1, 1973, through December 31, 2008). A total of 2 060 354 Danish and 2 944 675 Swedish children who survived the first 6 months of their life were included. We excluded 14 children who died of the same external cause as their siblings within 30 days. Data were analyzed from November 2, 2015, through October 14, 2016.

EXPOSURES

Participants were classified as exposed if a sibling died in childhood (age <18 years).

MAIN OUTCOMES AND MEASURES

Poisson regression was used to estimate mortality rate ratio (MRR) with the exposure as a time-varying variable.

RESULTS

Among the 55 818 participants who experienced sibling death in childhood (51.5% male and 48.5% female; median age at loss, 7.0 [interquartile range, 3.3-12.1] years), all-cause mortality risk was increased by 71% (MRR, 1.71; 95% CI, 1.57-1.87) during the follow-up of 37 years. The excess mortality risk was observed for groups with specific causes of death, and the higher MRRs were found when the sibling pairs died of the same cause (death due to disease [MRR, 2.16; 95% CI, 1.87-2.49]; death due to external cause [MRR, 1.91; 95% CI, 1.54-2.37]). The increased mortality risk after sibling death was seen across the follow-up period, regardless of the age at bereavement and the type of death among bereaved siblings, but the magnitude of association was stronger during the first year after sibling death (MRR, 2.51; 95% CI, 1.79-3.54). Higher MRRs were found among sibling pairs with the same sex (MRR, 1.92; 95% CI, 1.70-2.18) and close age (MRR, 1.94; 95% CI, 1.58-2.37).

CONCLUSIONS AND RELEVANCE

Bereavement in childhood because of the death of a sibling was associated with an increased risk for mortality in the short and long term. Health care professionals should be aware of individuals' vulnerability due to sibling death, especially for sibling pairs of close age or the same sex. Social and health care support may help to minimize the potential adverse effects on the bereaved sibling.

Prenatal maternal bereavement and mortality in the first decades of life: a nationwide cohort study from Denmark and Sweden

BACKGROUND

The loss of a close relative is one of the most stressful life events. In pregnancy, this experience has been associated with a higher risk of fetal death and under-five mortality, but little is known about potential effects on long-term mortality in offspring. We examined the association between prenatal maternal bereavement and mortality in a cohort of 5.3 million children followed until up to 37 years of age.

METHOD

The population-based cohort study included 5 253 508 live singleton births in Denmark (1973-2004) and Sweden (1973-2006). Children born to mothers who lost a child, spouse, sibling, or parent during or 1 year before pregnancy were categorized as exposed.

RESULTS

Prenatal maternal bereavement was associated with a 10% increased all-cause mortality risk in offspring [mortality rate ratio (MRR) 1.10, 95% confidence interval (CI) 1.03-1.18]. The association was the most pronounced for children of mothers who lost a child/spouse (MRR 1.28, 95% CI 1.14-1.44) and was stronger during the first 10 years of life. Prenatal maternal bereavement may have stronger effects on natural causes of death in offspring, including infectious/parasitic disease (MRR 1.86, 95% CI 1.07-3.23), endocrine/nutritional/metabolic diseases (MRR 3.23, 95% CI 2.02-5.17), diseases of nervous system (MRR 3.36, 95% CI 2.47-4.58), and congenital malformations (MRR 1.39, 95% CI 1.08-1.80). No excess mortality risk in offspring was observed for unnatural causes of death.

CONCLUSION

Prenatal maternal bereavement was associated with an increased long-term mortality risk in offspring, particularly for selected natural causes of diseases and medical conditions. Our results support the fetal programming hypothesis that prenatal stress may contribute to ill health from physical diseases later in life.