Quantitative genetic analysis of injury liability in infants and toddlers

Early-Life Temperamental Differences as Longitudinal Predictors of Unintentional Injuries

OBJECTIVE

Unintentional injuries are the leading cause of hospitalization and death among children. Compared to environmental factors, less attention in injury preventive efforts has been paid to how individual characteristics relate to the risk of injury. Using a large prospective cohort, the current study assessed the longitudinal impact of early-life temperament on the cumulative number of injuries until mid-adolescence.

METHODS

The data came from the European Longitudinal Study of Pregnancy and Childhood (ELSPAC-CZ). Temperament was evaluated by mothers when children were 3 years old (N = 3,545). The main outcome was the pediatrician-reported sum of child's injuries from age 3 to 15 (seven timepoints). Latent profile analysis (LPA) was used to determine classes based on temperamental dimensions and then extended to a mixture model with a distal count outcome. The covariates included maternal conflict and attachment, sex, family structure, and maternal education.

RESULTS

The LPA determined the existence of three classes: shy children (8.1% of the sample; lowest activity/highest shyness), outgoing children (50.8%; highest activity/lowest shyness), and average: children (41.1%; middle values). Results from a mixture model showed that the outgoing temperament was associated with the highest longitudinal risk for injuries, as both average children (IRR = 0.89 [0.80, 0.99]), and the shy children (IRR = 0.80 [0.68, 0.95]) had lower risk.

CONCLUSIONS

Early childhood temperamental differences can have long-term effects on injury risk. Highly active children showed the highest risk for future injuries, suggesting that these characteristics make them more likely to be involved in novel and potentially dangerous situations.

Nature, Nurture, and Expertise

Rather than investigating the extent to which training can improve performance under experimental conditions ('what could be'), we ask about the origins of expertise as it exists in the world ('what is'). We used the twin method to investigate the genetic and environmental origins of exceptional performance in reading, a skill that is a major focus of educational training in the early school years. Selecting reading experts as the top 5% from a sample of 10,000 12-year-olds twins assessed on a battery of reading tests, three findings stand out. First, we found that genetic factors account for more than half of the difference in performance between expert and normal readers. Second, our results suggest that reading expertise is the quantitative extreme of the same genetic and environmental factors that affect reading performance for normal readers. Third, growing up in the same family and attending the same schools account for less than a fifth of the difference between expert and normal readers. We discuss implications and interpretations ('what is inherited is DNA sequence variation'; 'the abnormal is normal'). Finally, although there is no necessary relationship between 'what is' and 'what could be', the most far-reaching issues about the acquisition of expertise lie at the interface between them ('the nature of nurture: from a passive model of imposed environments to an active model of shaped experience').

Twins' injuries: genetic and environmental risks / twin research reports / human interest stories

The relative contributions of genetic and environmental factors to unintentional injuries are of interest to families with young twins. A recent study found that childhood injuries are explained mostly by child-specific environmental factors. Next, twin research reviews of the association between periodontal disease and cancer, secular trends in gestational age and birthweight, and language development in hearing and deaf co-twins are also summarized. Interesting reports of newborn twins, twin-like relationships, twin interactions and missed twin relationships are presented.

Why carry out a longitudinal birth survey?

In spite of technological progress throughout the world, ill health, both physical and mental, is widespread - but much of this is preventable. With rapid globalization, populations in both industrialised and developing countries are being exposed to various stresses and to new environmental factors, such as those related to climate change and to an increasing range of chemicals of unknown effect. There is substantial evidence that exposures to environmental risk factors in pregnancy and childhood have a major influence on health and development even into adulthood and future generations. In this paper we discuss the importance of longitudinal studies in identifying the processes underlying health and developmental problems and thus, by using the strengths of birth cohort studies, identifying preventative and other strategies which will protect public health from adverse environmental influences.

Distribution of accidents, injuries, and illnesses by family type. ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood

OBJECTIVE

To investigate whether family type and psychosocial risks indexed by family type were systematically associated with differences in health outcomes in children.

DESIGN AND SUBJECTS

The study is based on a longitudinal, prospective study of a large (n = approximately 10 000) community sample of families, the Avon Longitudinal Study of Pregnancy and Childhood.

MAIN OUTCOME MEASURES

Frequency of accidents, illnesses, and medical interventions.

RESULTS

At 2 years of age, children in single-parent and stepfamilies were disproportionately likely to experience accidents and receive medical treatment for physical illnesses. In addition, children in single-parent families and stepfamilies were more likely to be hospitalized or receive attention from a hospital doctor for an injury or illness. Exposure to psychosocial risks also were elevated in single-parent families and stepfamilies, compared with intact or nonstepfamilies, and these factors primarily accounted for the connection between family type and children's physical health.

CONCLUSIONS

The consequences of family transitions on children's health extend beyond traditional mental health and behavioral outcomes and include accident proneness, illness, and receipt of medical attention. The mediating processes are not entirely attributable to social class differences connected to family type and may instead be associated with a range of psychosocial risks that are more frequently found in single-parent families and stepfamilies, compared with intact or nonstepfamilies. Prevention and intervention efforts directed toward children at risk for poor behavioral and mental health adjustment secondary to family disruption should consider children's physical health and health-related behaviors.

Genetics and behavioral medicine

Genetics has substantial relevance to behavioral medicine. A rapidly growing body of evidence indicates the influence of genetics on health and disease and on the behavioral factors related to them. The model of quantitative genetics provides a general interpretational scheme for this burgeoning field. The model focuses on variability, and a major research objective is the decomposition of observed individual differences into portions attributable to various types of genetic and environmental sources of variability. This approach emphasizes the coaction of genes and environments and stands in sharp contrast to the archaic view that places nature and nurture in opposition. Some relevant examples are given in this first article to illustrate the general analytic process. A detailed application to cardiovascular health and disease is provided in the second article, and some policy implications are briefly considered in the third article.