In this nationwide population-based cohort study we show that the association between parity and health in old age differs for different health outcomes, that is, between the risk of first hospitalisation and the risk of re-admission and mortality. While it is known that childless old people have higher mortality, this study indicates that this may result from a shorter survival once a disease has occurred. If hospitalisation is a proxy for disease onset, our results further suggest that childless individuals do not necessarily face an earlier disease onset. In addition, this study demonstrates that adult children’s educational level is important for both hospitalisation as well as survival, in fact more so than the number of children itself. Finally, our results indicate that offspring’s socioeconomic resources explain part of the curvilinear relationship between parity and later life mortality observed in this and in previous studies.
The finding that childless individuals have a higher mortality than parents is in line with previous studies [4]. Only among the small group of parents with five or more children (less than 3% of the study population), we found no reduced mortality compared to childless. A complex interplay of selection processes and biological and social effects of parity may result in an ‘optimal’ number of children for parental mortality [4]. To our knowledge, parity in relation to risk of hospitalisation, re-admission and mortality after hospitalisation has not previously been studied. As such, we cannot draw comparisons with previous work. It has been hypothesised that having children may promote healthier behaviours in parents [26], which may contribute to a delay in onset of disease. Our results do not support this hypothesis since the hospitalisation risk was not lower for parents than for childless individuals. It should be noted, however, that hospitalisations are not an ideal measure of disease onset and that the probability of hospitalisation may differ between parents and childless individuals regardless of disease status.
Having three or more children was associated with a greater risk of hospitalisation than having one child. This could be related to the balance between the positive effects of having children and selection processes defining the social background and composition of this group of parents [4] which results in a greater risk of hospitalisation but lower mortality. Alternatively, children could assist their parents with seeking inpatient care for existing health problems or with transport to the hospital.
Health selection into parenthood could be an explanation for differences in morbidity and mortality between parents and childless individuals, but is less likely that selection explains disparities in survival once a disease has occurred. The observed associations between having children and re-admission or survival after hospitalisation might thus suggest support from children to matter for prognosis after disease onset. However, these findings might also stem from a difference in the probability of becoming hospitalised. Adjusting for parents’ own education and income had almost no impact on the increased mortality of childless individuals. This, too, may indicate that selection into parenthood or an accumulation of disadvantage over the life-course is not the only force behind the survival disadvantage among individuals without children, but that support from adult children also matters.
Consistent with previous studies we found adult children’s education to be more closely related to parental mortality than children’s income [14, 22]. Building on this earlier work, our results show that education of adult children is associated with both disease onset in parents and with survival after ill health has begun. Even though the children’s socioeconomic resources seem to matter more for health in old age, the associations with number of adult children remained after adjusting for children’s education and income. This suggests that the number of children, independent of their socioeconomic resources, matters for the survival of their parents, but perhaps through different mechanisms.
In Sweden, elderly care is universally available and almost fully subsidised. Differences in access to health and elderly care are therefore less likely to explain the results than in other contexts. However, a publically financed health care system also comes with limitations of resources and a slim lined organisation that could increase differences between individuals with and without family support. Although cohabitation of adult children with their parents is uncommon in Sweden, the majority of parents has contact with their children at least once per week [27, 28]. Moreover, adult children often become care-givers for their aging parents [11]. Still, it is possible that children and their socioeconomic resources play an even larger role for their parents’ health in countries in which care is not publically financed. In order to gain further insight in the relationship between childlessness, health, and survival in old age we suggest future studies continue looking into mechanisms linking adult children to parental health and focus, for instance, on the different types of support that could affect health in old age. In an era in which childlessness is increasing [29] this is important to inform public health policies and reduce survival inequalities.
Strengths and limitations
This large population-based cohort study has complete information since it is based on national register data, and therefore a low risk of exposure and outcome misclassification or selection bias. It is the first study, to our knowledge, to examine and compare the risk of hospitalisation, re-admission, and mortality after hospitalisation among parents compared to childless individuals. Nonetheless, there are some limitations of the work. It could be argued that hospitalisations are a poor proxy for disease onset. For example, some people could experience disease onset without being admitted to hospital, while other people may be admitted to hospital for relatively minor difficulties. However, requiring hospitalisation for at least two nights ensured some degree of severity, and the publically financed healthcare in Sweden ensures equal chances of being admitted for everyone. Thus, we believe both specificity (all with a severe condition are hospitalised) and sensitivity (the hospitalised are truly ill) are high given the definition of onset of severe disease. It could further be argued that adult children’s socioeconomic resources are proxy measures of their parent’s socioeconomic position, rather than an independent exposure. However, if this was the case we would expect similar associations with both adult children’s education and income. The fact that we observed associations with parental outcomes for adult children’s education but not income suggests that the mechanisms driving these associations are related to adult children’s education per se. It should, however, be noted that the inequality in income is rather low in Sweden compared to other countries. Adult children’s income might perhaps play a larger role for parental health in other contexts.