Unlike in the established literature, child abuse was not found to be significantly related to deficits in childhood height in the 1958 cohort141-145. Though there was some
indication, in both the complete and sensitivity analyses, that child abuse may be associated with deficits in height. The discrepancy in results could reflect
methodological variations. In previous studies, the relationship has been examined using specialised cohorts, where cases of child maltreatment have been ascertained using agency reports. Whereas a large national sample was used in this study, and participants self-reported abuse retrospectively at age 45y. As the 1958 cohort is a population cohort, it is expected that there are fewer cases of child abuse and neglect than in targeted samples, such as foster care cohorts. In addition, findings from Chapter 4 suggest the child maltreatment may have been under-estimated in the 1958 cohort due to sample attrition. It is also possible recall bias could have affected the relationship, as abused participants may not have reported their maltreatment experiences and
consequently were misclassified as not abused, therefore weakening the association323;330.
In the 1958 cohort, indicators of neglect and household dysfunction at age 7y were associated with short stature at all ages. However, the association was largely
explained by confounding factors. In particular, the strength of association weakened after adjustment for prenatal factors, such as birth weight, pre-term birth, maternal smoking during pregnancy and socio-economic circumstances, i.e. social class at birth and household crowding at age 7y. Previous studies have shown that the relationship between adverse childhood experiences and height growth attenuates after accounting for socio-economic disadvantage152. For example, a Swedish survey found that the association between parental divorce/separation and shorter adult stature was
attributable to financial hardship associated with changes to the family structure, and not family conflict352.
Nevertheless, an independent association was found between indicators of neglect at age 7y and deficits in childhood height after adjustment for demographic and socio- economic factors, with the effect persisting into adulthood for some measures. Effect
established literature: for example in the 1958 cohort neglect measures were associated with childhood (age 7, 11 and 16y) height deficits of 0.07-0.34 SD compared to ≥ 2 SD (age 0-14y) elsewhere141;142;144. Differences in the strength of association may reflect variations in study samples (clinical/foster vs. population) and methods of case- ascertainment (agency vs. parent/teacher-reports). The severity of neglectful experiences may also have differed, as 7y measures in the 1958 cohort are indicator variables and do not directly measure neglectful behaviour. Severity of experiences has been shown to be an important moderator in the relationship between child
maltreatment and behavioural outcomes433. Here, a cumulative effect of prospective neglect measures was found, suggesting that an increase in the number of neglectful experiences, and thus severity, was associated with greater deficits in height at each age.
Previous studies have found a cumulative effect of adverse childhood experiences on other aspects of child development192, including behavioural433 and emotional
development486. No study has examined the cumulative effect of child maltreatment and household dysfunction on height growth. In the 1958 cohort, adversity score was negatively related to childhood and adult stature. For each additional neglect or household dysfunction measure at age 7y, height decreased by ≈ 0.3cm in childhood and 0.1cm in adulthood. Researchers have suggested that a cumulative risk model may predict more variability in behavioural outcomes associated with adverse childhood experiences than agency reports of child maltreatment192
. In the 1958 cohort, there was little difference in the cumulative effect of indicators of neglect at age 7y on height compared to adversity score at age 7y: increases in neglect and adversity score at age 7y were both associated with ≈ 0.3cm deficit in childhood height in both genders.
Therefore, the cumulative effect of neglect may be more strongly associated with deficits in height growth compared to the overall level of adversity (neglect and household dysfunction).
There are several possible mechanisms by which childhood neglect may influence child-to-adult height trajectories. The relationship between neglect and height growth may reflect the impact of socio-economic disadvantage, for which a relationship with height has been established152;207;231. The relationship with short stature found for prospective neglect measures, but not for retrospective measures, suggests that
supporting findings from Chapter 4. Childhood neglect measures may have a stronger association with socio-economic disadvantage compared to those collected at age 45y. Indeed, the relationship between 7y neglect measures and child-to-adult height
trajectories mirror findings from a previous study of the 1958 cohort which investigated the association between early socio-economic circumstances and height growth152. Li et al found that low social class at birth and household crowding at age 7y were related to deficits in childhood height. As with childhood neglect measures, the strength of association between socio-economic disadvantage and height decreased by adulthood, with catch-up growth following a period of early delay152. Child neglect may be an additional component of socio-economic disadvantage, alongside other aspects of material and social deprivation, which has an additional effect on height growth.
Failures to provide adequate nutrition or medical treatment are important components of physical neglect, and are also related to socio-economic disadvantage265. Thus, deficits in height may represent the presence of chronic malnutrition or long-standing health issues associated with child maltreatment. There is also some evidence to suggest that a stress response to neglect may affect activation of the hypothalamic-pituitary-adrenal (HPA) axis. It has been hypothesised that cortisol, secreted in response to chronic stress, may inhibit pituitary growth hormone (GH) release, and decrease target tissue sensitivity to GH, somatomedic-C or other growth factors153;488;489;489;490;490;491.
However, physiological mechanisms by which neglect may influence height growth are not well understood.
It is also possible that the effects of material and social deprivation, such as an inadequate diet, may underlie the associations found between childhood indicators of neglect and height growth. The residual effect of neglect on height may be attributable to unmeasured confounding factors or other aspects of socio-economic disadvantage. For example, information on childhood diet was not collected in the 1958 cohort. In addition, it may not be possible to disentangle the separate effects of neglect and socio- economic disadvantage due to the complexity and overlap in constructs29;301;302. Thus the results may reflect the impact of neglect and socio-economic disadvantage on child- to-adult height growth.
5.5.3 Conclusion
In summary, adverse childhood experiences were inversely associated with height growth. Although some of the associations were explained by demographic and socio- economic factors, an independent association persisted for some neglect and household dysfunction measures. A dose-response relationship indicates that the cumulative effect of neglect experiences was associated with child-to-adult height trajectories. Results from this study also highlight the importance of using a wide-range of adverse
childhood experiences. A stronger association of adverse childhood experiences with childhood height compared to adult height indicates that growth deficits may diminish over time due to catch-up growth. Thus it is important to examine the influence on child-to-adult height trajectories as examining height at one age may fail to capture the full effect of the exposure. It is uncertain whether delays in growth may underlie the relationship between adverse childhood experiences and adult disease risk, but findings from this study suggest that it is a potential area for future research