Was Cinderella just a fairy tale? Survival differences between stepchildren and their half-siblings

Abstract

The death of a parent, particularly the mother, is linked to a suite of negative outcomes across the life-course. Compounding concerns for child outcomes are expectations of poor treatment by step-parents after parental remarriage. Indeed, folk tales of step-parental abuse abound cross-culturally and are embedded into stories taught to children. To understand why child outcomes might be sensitive to levels of relatedness within the household, evolutionary-oriented research targets patterning in parental expenditure in ways predicted to maximize inclusive fitness. In particular, parents are expected to prioritize investments in their biological children. However, stepfamilies are only formed after children experience multiple unfortunate events (e.g. parental loss, poverty), blurring causal interpretations between step-parental presence and stepchild outcomes. Moreover, stepchildren have been shown to be integral to household functioning, caring for their half-siblings and stabilizing relationships. These results challenge narrow views of adaptive behaviour; specifically, that step-parents, unlike biological parents, do no stand to reap fitness benefits from the care that they provide to their stepchildren. To evaluate these critiques, we analyse the survival outcomes of stepchildren. We include over 400 000 individuals from across a natural fertility period (1847–1940) in the United States state of Utah and examine the consequences of parental loss and step-parental introduction. Our analyses yield three key results: (i) exposure to maternal loss in childhood is associated with elevated mortality risk, (ii) parental remarriage does not increase the risk of mortality among stepchildren compared to non-stepchildren who too had lost a parent, and (iii) stepchildren enjoy higher survival than their half-siblings within the same family. Ultimately, this work contributes to the increasingly recognized importance of cooperative relationships among non-kin for childcare and household functioning.

This article is part of the theme issue ‘Multidisciplinary perspectives on social support and maternal–child health’.

1. Introduction

Among mammals, human offspring are particularly altricial, slow to develop and expensive in terms of both the time and resources necessary for them to achieve independence [1,2]. The costliness of children during their dependence necessitates support from beyond their biological mothers, often resulting in biparental care where both mothers and fathers support children's survival and development [3–5]. However, decision making among parents regarding optimal parental expenditures, and the consequences for offspring outcomes, is a contentious subject. The role of mothers versus fathers varies across societies, as do patterns of child survival and pace of development [6–9], resulting in a complex set of interacting parts that can cause child outcomes to differ across time and place because of variability in parent–child relationships.

One way to distinguish more clearly the roles of mothers and fathers on child outcomes is to observe the consequences of parental death [10]. While claims of human universal phenomenon are difficult given our behavioural variability across cultures, what can be said with certainty is that children who experience parental loss typically suffer a suite of negative outcomes that are distinct from those who do not. Given the dependence of children on their mothers, maternal loss increases child mortality risk, particularly during infancy (reviewed in [11]). Paternal loss, however, does not affect infant survival as strongly, or as uniformly, across studies; instead, the absence of a father is more often linked to negative outcomes later in childhood and well into adulthood, particularly where monogamy is normative and/or fathers provide the bulk of financial resources. For example, paternal loss is often linked to lower educational attainment, greater involvement in criminal or delinquent activities and elevated levels of poverty across the life-course [12–14].

These adverse outcomes are driven by multiple factors in parental loss households; however, reduced levels of parental care coupled with economic instability appear to be key drivers [15]. A seemingly straightforward means to gain back biparental care and economic stability (at least partially) is to reintroduce a parent into households where one has been lost. However, while remarriage by the remaining parent may mediate some of the negative effects of parental loss, these gains may be overshadowed by the potential costs owing to the introduction of a step-parent into the household [16]. This new family also often includes additional children who too require resources and attention from parents. Because not all family members are related, conflict within the household over resource allocation is anticipated, resulting in mortality differentials possibly emerging in step-structured households [17].

To explain why child outcomes might be sensitive to levels of relatedness within the household, evolutionary-oriented researchers argue that parental expenditure should be allocated in ways expected to maximize inclusive fitness [18–21]. In particular, parents are expected to prioritize investments in their biological children. In support of this, stepchildren have been shown to experience higher rates of abuse, neglect and mortality than children in households with two biological parents [22]. This relationship has been dubbed the Cinderella Effect [23] in-line with folk tales of step-parental antipathy and mistreatment that are common cross-culturally and embedded into stories taught to children (e.g. fairy tales) [24].

However, there are multiple critiques of this argument and evidence presented. Stepfamily households are often formed only after the experience of multiple unfortunate events (e.g. parental death and poverty). Together, these factors may contribute to a poorly functioning family unit, blurring simple causal interpretations [25,26]. Moreover, stepchildren are often overlooked as important contributors to household functioning and stability. This oversight is surprising given that over 40% of adults in the United States (US) have a step-relationship [27], and that this value is probably even higher in many small-scale, preindustrial societies (greater than 50%), as well as in the past [28,29]. For example, stepchildren provide social, emotional and economic support to their half-siblings from childhood to adulthood, continuing even after the death of their stepparent [30]. Additionally, research targeting stepfathers find their financial investment in current stepchildren to be proportionate to their genetic children from a previous relationship [31]. While difficult to interpret through the lens of the Cinderella Effect literature, these researchers highlight that investments in non-biological children can be fitness enhancing by way of, for example, signalling relationship commitment in order to develop and maintain a second marriage (which is often more fragile than the first). Altogether, this work highlights that relatedness is not a necessary condition for realizing fitness pay-offs to investment in or cooperation among household members [32,33].

Parental loss, family reformation, the presence of a step-relative and investment in non-biological kin are recurrent themes faced by individuals and families across place and time. Accordingly, expectations of step-parental neglect may be based on a narrow view of adaptive behaviour, specifically that parenting behaviour is only optimized when directed towards biological kin (sensu [34]). However, the question remains as to the outcome of stepchildren. Typical expectations are that stepchildren will be worse off than biological children in response to reduced parental investment. However, given possible pay-offs to stepchild investment, step-parental solicitude may be an adaptive means to stabilize a tenuous relationship and foster household cooperation, thereby, possibly even indirectly, benefitting the stepchild. Accordingly, to make sense of these competing claims, we present and evaluate several predictions targeting the survival outcomes of those who experience parental loss, specifically focusing on stepchildren. That is, do stepchildren experience more adverse outcomes compared to other children, or instead does remarriage and the presence of a step-parent offer benefits?

Our analyses are divided into three distinct phases to answer very specific aspects of stepchild survival using data from the Utah Population Database. First, because the general literature on parental loss reports that children and families who experience traumatic events are at greater risk for more negative outcomes, we expect that children who lose a parent will be at a survival disadvantage compared to those who do not. Moreover, given that investments by mothers are of greater importance for child survival, we hypothesize that children who lose a mother will be at a greater survival disadvantage compared to those who lose a father. With this initial analysis, we do not yet evaluate support for the Cinderella Effect; instead, we use this as an analytical entry point into the topic and a way to evaluate well-established relationships by way of our dataset. Thus, for our first set of analyses, the question is simply whether children who experienced the death of a mother or father in childhood face worse survival in relation to children who did not.

The second set of analyses focuses exclusively on the subset of egos whose parents died when they were children. Our attention here is on the role of remarriage, or not, and its influence on the survival of these two types of bereaved children. Put simply, egos with a widowed parent may see the surviving parent remarry. Our question is whether remarriage affects the survival of these children. Within the literature, quite often negative effects are reported for children in response to parental remarriage and their change in status to ‘stepchild'. To isolate appropriately the effect of becoming a stepchild from other life events, we focus on comparing stepchildren to other children who too have experienced parental loss, but whose surviving parent has not remarried. Unsurprisingly, past research has found negative effects for stepchildren when compared to children who have never experienced parental death and the associated social, economic and emotional hardships [35]. Here, we remedy this by comparing the survival of children only among those who have lost a parent.

In the third portion of the analysis, we explicitly target central claims from the Cinderella Effect literature. To do so, we make survival comparisons between sibling types within the same household. That is, within a stepfamily, are stepchildren at a survival disadvantage compared to their half-siblings (who are the product of ego's biological parent and step-parent in the new family)? A key prediction from the Cinderella Effect literature is that stepchildren will experience reduced survival compared to half-siblings, particularly when a stepfather is present [23].

In sum, increasingly well-documented are the contributions of those other than biological parents for successful childrearing and household functioning. Accordingly, we are interested in evaluating the expectation that parenting behaviour is optimized when directed towards biological kin. Specifically, we apply predictions from the Cinderella Effect literature, targeting stepchild outcomes compared to their half-siblings, to examine expectations of step-parental antipathy and neglect directed towards unrelated children in the household.

2. Data

For this study, we use the Utah Population Database (UPDB) to examine the relationship between child status (e.g. stepchild, full biological child) and survival. This analysis is performed in three stages: consequences of parental loss, effects of step-parent introduction and a within-stepfamily sibling comparison analysis. The UPDB is housed at the Huntsman Cancer Institute at the University of Utah and is a unique and comprehensive source of in-depth information on individuals and families that supports research on genetics, epidemiology, demography and public health. The central component of the UPDB is an extensive set of genealogies in which family members are linked to demographic and medical information. The genealogies are based on a combination of original genealogical data of the founders and their descendants in the state of Utah, derived from the Genealogical Society of Utah, and extensive use of birth certificates derived from state vital records.

In this study, we use data from children younger than 18, born between 1847 and 1940, and their siblings (n = 416,325) to assess survival probabilities across three sets of analyses (detailed below). We target this time period because it is marked by natural fertility, large families and an agrarian lifestyle—all characteristic traits of the family and economic conditions from which folk tales of step-parental mistreatment emerged. During the frontier-period of Utah, fertility was initially high (mean = 8.9, s.d. = 2.9; 1850–1859) and women married in their late teens and early twenties. Children were important sources of agricultural labour and were also caretakers for younger siblings (particularly older sisters; [36]). Consistent with other regions of the US, as populations increasingly urbanized, fertility declined in Utah (mean = 5.7, s.d. = 2.7; 1930–1939) as women married later, increased their interbirth intervals and/or stopped reproducing sooner [37]. Important to note is that Utah fertility rates were higher than US fertility generally across this time period. This is, in part, attributed to prenatal and prosocial religious practices among members of the Church of Jesus Christ of Latter-day Saints (LDS) who compose approximately 60% of our sample. Accordingly, we control for this religious affiliation in our analyses. Additionally, while polygyny was practiced by some men during the nineteenth century, data employed here only includes children born into monogamous marriages. Lastly, we also include other control variables, in addition to the covariates necessary to evaluate Cinderella Effect predictions, because of their known association with childhood mortality (detailed below; [38]).

3. Analysis and results

(a). Consequences of parental loss

The broader question posed in this study deals with the well-being and survival of stepchildren. The precipitating event which creates the circumstances for stepchildhood is the death of a parent. Accordingly, here we examine the effect of parental death on child survival. Table 1 provides descriptive statistics for the sample under analysis comprising 203,747 girls and 212,578 boys. Approximately, 9% of these children experienced the death of their father prior to age 18 while nearly 6% lost their mothers.

Table 1.

Descriptive statistics by sex (n = 416,325).

	female (n = 203,747)	male (n = 212,578)
died before the age of 18	21,874 (10.7%)	24,094 (11.3%)
follow-up time to the age of 18 (months)	199.8±51.9	197.9±55.0
birth year	1905.2±22.7	1905.4±22.9
birth order	4.3±2.9	4.3±2.9
father's membership in the Church of Jesus Christ of Latter Day Saints (LDS)	129,503 (63.6%)	135,215 (63.6%)
mother's membership in the Church of Jesus Christ of Latter Day Saints (LDS)	134,078 (65.8%)	139,936 (65.8%)
number of full siblings	7.8±3.2	7.8±3.1
father died before the age of 18	18,097 (8.9%)	18,896 (8.9%)
- mother remarried before the age of 18	1,315	1,281
- half-brother born before the age of 18	675	655
- half-sister born before the age of 18	670	677
mother died before the age of 18	12,127 (6.0%)	12,211 (5.7%)
- mother remarried before the age of 18	3,640	3,782
- half-brother born before the age of 18	2,630	2,739
- half-sister born before the age of 18	2,643	2,754

Table 2a summarizes sex-specific Cox regression models for childhood mortality between the ages of 28 days and 18 years of age (see the electronic supplementary material, table S1 for a full model summary). We did not include the first month of life as part of the follow-up in order to focus on mortality that was not the immediate consequence of maternal mortality during childbirth. We also excluded those whose death was within 31 days of parental death because this pattern is typically driven by infectious disease within a household and not parental investment decisions. Parental mortality for these models is treated as a time-varying covariate. Included in our models are controls for birth year, birth order, maternal age at birth and parental LDS status. Interactions with child age were included for variables that did not satisfy the proportional hazards assumption. We find, summarized in table 2a, that for both sons and daughters, the death of a mother is associated with excess mortality before the age of 18 in relation to children whose mother was still alive over this interval. Significant effects were not found for paternal mortality.

Table 2.

Cox models of mortality from 28 days to 18 years (parental loss and remarriage models) using time varying dataset. (***p < 0.001; **p < 0.01; *p < 0.05.)

	daughters	sons
(a) parental deatha
n children	203,747	212,578
n child deaths	21,874	24,094
likelihood ratio (LR), degrees of freedom (d.f.)	4027***, 10	4182***, 12
hazard ratio (HR) (95% CI)
- mother dies	1.55 (1.31, 1.83)***	1.89 (1.61, 2.22)***
- mother dies × child age	1.00***	1.00***
- father dies	1.07 (0.97, 1.17)	1.00 (0.90, 1.10)
(b) mother's remarriage modelb
n children	16,408	16,973
n child deaths	538	455
LR, d.f.	78.81***, 17	42.35***, 19
HR (95% CI)
- mother remarries	1.13 (0.62, 2.04)	0.99 (0.54, 1.81)
(c) father's remarriage modelc
n children	10,992	10,912
n child deaths	481	481
LR, d.f.	80.27***, 17	57.59***, 17
HR (95% CI)
- father remarries	1.07 (0.77, 1.49)	0.97 (0.68, 1.37)

^aModel was additionally adjusted for birth year, birth order, maternal age at birth, and parental Latter-Day Saints (LDS) status. Interactions of birth order and maternal age at birth with child age were also added to the sons model because these predictors did not fulfill the proportional hazards assumption.

^bModel was additionally adjusted for birth year, birth order, maternal age at birth, parental LDS status, number of full siblings, presence of an older brother, presence of an older sister, presence of a stepbrother, presence of a stepsister, birth of a half-brother (time-varying), birth of a half-sister (time-varying), and mother surviving to the child turning 18 (time-varying). Interaction of birth year with child age was added to the daughters model and interactions of birth year and mother surviving to the child turning 18 with child age were added to the sons model because these predictors did not fulfill the proportional hazards assumption.

^cModel was additionally adjusted for birth year, birth order, maternal age at birth, parental LDS status, number of full siblings, presence of an older brother, presence of an older sister, presence of a stepbrother, presence of a stepsister, birth of a half-brother (time-varying), birth of a half-sister (time-varying), and father surviving to the child turning 18 (time-varying). Interaction of birth year with child age was added to the daughters model and interactions of birth year and presence of a half-brother were added to the sons model because these predictors did not fulfill the proportional hazards assumption.

(b). Effects of step-parent introduction

The next phase of analysis includes only those children who lost a parent to death prior to the age of 18, hence a smaller sample reflecting this restriction. In table 2b,c, we show sex-specific results of the child for father death/mother remarriage and mother death/father remarriage models, respectively (electronic supplementary material, tables S2 and S3). These Cox regression results treat a remarriage event as a time-varying covariate. Controls, in addition to those listed for the model above, include the number of full siblings, the presence of an older brother, the presence of an older sister, the presence of a stepbrother, the presence of a stepsister, the birth of a half-brother (time-varying), the birth of a half-sister (time-varying) and whether the surviving parent dies prior to the child turning 18 (time-varying). We find no evidence that a child's sex or the sex of the remarrying parent affects child survival. Thus, the introduction of a step-parent does not reduce child survival. Specifically, stepchildren are not at higher risk than other children who too have lost a parent.

(c). Within-family sibling comparison

A useful model for comparing the survival of stepchildren versus biological children is the use of fixed effects models where the step and biological children are contrasted within a family. This specification is attractive because it allows us to isolate the survival differences between these two types of children while simultaneously controlling for common characteristics shared between them such as parental and family traits and any other unobservable yet stable characteristics. Thus, for our analysis, we target families where there were both stepchildren and the shared, biological children of both parents (i.e. the half-sibling of the stepchild). Here, we structure the file so that we can group all sibships that contain both step and biological children within a given family and then apply Cox regressions stratified by families and additionally adjusted for sex, birth year, parental LDS status, number of full siblings, number of half-siblings and number of stepsiblings. We find that, within the same family, stepchildren have significantly lower rates of mortality than their half-siblings. The protective effects of being a stepchild are comparable whether it was the mother (hazard ratio (HR) = 0.29, confidence interval (CI) = 0.24, 0.35) or the father (HR = 0.25, CI = 0.18, 0.36) who was the surviving parent (see the electronic supplementary material, table S4 for a full model summary). As a note, one of the artefactual aspects of this specification is that the sequence of the first marriage, birth, parental death, remarriage and new birth means that the children from the first marriage are going to be older, by definition, than the children born from the newly formed (second) marriage at the time of the birth of the new half-siblings. As we constructed the file, we required that the children born from the first marriage, who later became stepchildren, had to survive long enough to be present when children from a second marriage were born so that parents were faced with resource allocation questions between the two types of children. This requirement means that the children from the first marriage have a mortality hazard rate of zero since they must live to the time when their half-siblings are born.

To improve the within-family model specification, we imposed more stringent criteria where we compare the last-born child from the original marriage to the first-born child from the newly constituted marriage; the former being the stepchild (to the new parent) and the latter being the half-sibling (the biological child of both parents from the newly formed family). We further required that the comparison of mortality be restricted to those years where both had to have lived to some minimum age, specifically the age the stepchild was when his/her half-sibling was born. For example, if the stepchild lived to the age of five before the (latter) half-sibling child was born, we would then compare survival from the age of five onwards for both individuals (i.e. mortality risk was compared beginning at the age of five). This ‘exposure alignment' is the basis of the sample used to conduct the final set of analyses.

We find that stepchildren with either a stepmother (HR = 0.20, CI = 0.04, 1.08; n = 3,354; electronic supplementary material, table S5) or stepfather (HR = 0.27, CI = 0.01, 9.12; n = 980; electronic supplementary material, table S6) experience no elevated risk of mortality. Further, when we pool across step-parent type, we find their presence to be protective for stepchild survival (HR = 0.22, CI = 0.05, 0.95; n = 4,334; electronic supplementary material, table S7). In figure 1, we display the results of this analysis by way of a survival curve showing that stepchildren have better survival than biological children (after exposure alignment). In other words, step-parents afford a survival advantage rather than a disadvantage to the stepchildren, an association not consistent with the Cinderella Effect.

Figure 1.

Paired sibling Cox model of stepchild survival compared to their half-siblings up to the age of 18 following age-related exposure alignment.

4. Discussion

Applying predictions from the Cinderella Effect literature, we targeted analyses on the survival of children in response to parental loss and step-parental introduction. First, we found that parental loss (specifically maternal loss) was indeed associated with elevated mortality risk in childhood. Second, we found that remarriage and the introduction of a step-parent into the household was not associated with increased mortality risk for stepchildren. Third, we found that stepchildren enjoyed higher survival probabilities than their half-siblings within the same family, even after exposure alignment.

These results run counter to previous research reporting negative outcomes for stepchildren. Differing findings may be driven, in part, by several factors including the apples to oranges effect, response bias in reporting, inappropriate labelling and the dissimilar role of divorce versus death on child outcomes. The apples to oranges effect to the problematic comparison of stepchild outcomes to children living in intact households with both biological parents [35]. Regularly, researchers report more negative stepchild outcomes through measures of education [39], mental health [40] and drug use [41]. However, as we find, stepchild outcomes are similar to children living in single-parent households (reviewed in [35]). Thus, claims that step-parents per se drive the poorer outcomes of stepchildren are not supported given that children who experience social, economic and emotional hardships associated with parental loss and/or single-parent households share similar fates. Moreover, response bias in reporting against step-parents has long been noted [42]. Behaviour between a parent and child that might seem appropriate to social and healthcare workers (e.g. physical reprimands) may be reported as abuse if observed happening between a step-parent and stepchild [43,44]). Additionally, research on stepchild outcomes regularly relies on data reported at the family level (e.g. [45]). This is problematic because the researcher assumes that the step-parent is the perpetrator, yet all that is known for sure is that a step-parent is present [46]. The research focused on individual relationships has found, for example, no significant difference between step and birth parents with regard to violence directed at children [43]. Lastly, here the precipitating event which creates the circumstances for stepchildhood is the death of a parent. Recently, however, stepfamilies more commonly form following divorce [47]. While this may be of relevance to predicting and interpreting stepchild outcomes, the literature rarely distinguishes between the two and, consequently, their relative effects have yet to be clearly disentangled. However, there has been research conducted on child outcomes generally (i.e. not specific to stepchildren) following parental death versus divorce. While the results are mixed with respect to outcomes [47,48], findings broadly indicate that both groups of children experience lower educational and economic attainment as adults compared to children from intact households [49–51].

An additional consideration is that support for the Cinderella effect primarily comes from WEIRD (Western, Educated, Industrialized, Rich and Democratic; [52]) settings where parental care is nuclear family based. However, there are numerous ways in which families and cultures across the world organize households to meet the emotional and physical needs of developing children [53]. In some groups, men rarely engage in childcare, only in resource provisioning, and instead these needs are met primarily by the mother and her extended female kin-network [7,54–56]. Sisters, grandmothers, aunts, cousins and more distantly related relatives jointly contribute, to varying degrees. However, in other groups, fathers contribute the bulk of childcare and mothers focus on the economic productivity of households [57]. Thus, the relative roles of mothers and fathers as caregivers versus resource providers, the stability of families and the tasks that children perform are all are important considerations for predicting stepchild/step-parent relationships. For example, in most agrarian economies children, both related and unrelated are necessary for household productivity. Not only do they serve as helpers in the field, they also serve as helpers in the home [58,59]. Accordingly, stepchild investments can be fitness enhancing by way of fostering household productivity through stepchild labour and childcare.

As mentioned earlier, Utah primarily operated through an agrarian economy during the time period under study here (although the state was becoming increasingly industrialized and urbanized). Family size was large and children were important sources of household labour, a key difference compared to modern Utah, and the US more generally, where fertility and child productivity have declined dramatically following demographic transition [36]. However, far from being an unusual time period or population under study, this dataset allows for an ideal test of Cinderella Effect predictions. The effect itself was named after folk tales of stepchild mistreatment from a time of large, farming families similar to those under study here [23]. Yet, when replicating many of the conditions under which the fairy tale emerged, we fail to find support for step-parental neglect. While time period, mode of production and family size are all probably important variables underlying costs versus benefits to step-parental investment, these nuanced considerations have yet to be incorporated into contemporary Cinderella Effect models.

Ultimately, cross-cultural variability in parenting strategies challenge straightforward generalizations of human universals regarding stepparent antipathy and neglect—specifically that parents should bias their investment towards biological children at the expense of other children in the household. What is increasingly well-documented is the dependency of any one individual on many others for his or her welfare. From infancy to death, humans are part of nested sets of social relationships necessary for individual health and household functioning [11,60,61]. These networks include kin, of course, but are also inclusive of non-kin: in-laws and friends. All too often overlooked is that for many, stepchildren are important components of one's network and while, at times, they may require more resources than they provide, they can easily compensate for this as they grow.

In sum, we argue that evolutionary models of parental investment need to be appropriately situated to human life-history patterns. Across time and place, the human family is regularly composed of step-structured households, reliant on investments from multiple individuals, including stepchildren. Thus, because step-parents are in part dependent on the productivity of stepchildren for successful household functioning, stepchild solicitude is an important component of fitness. The trade-offs individuals face when making parental investment decisions have long been studied across the social and biological sciences, yet we believe past research has been overly narrow in privileging fitness benefits tied to investment in kin.

Ethics

The research was approved by the University of Utah Institutional Review Board (IRB no. 00043524) as part of the ‘Early Life Conditions, Survival, and Health: A Pedigree-Based Population Study' (PI Smith).

Data accessibility

The UPDB is a unique research resource that enhances the value and furthers the advancement of research in studies linking early life circumstances to health and behavioural outcomes later in life. Special attention is given to protect individuals and their information contained within the UPDB and the organizations that contribute data while also allowing access to researchers. Accordingly, the Utah Resource for Genetic and Epidemiologic Research (RGE), established by the Executive Order of the Governor of Utah, administers access to the UPDB through a review process of all proposals using UPDB data. The protection of privacy and confidentiality of individuals represented in these records has been negotiated with agreements between RGE and data contributors. Data from the UPDB are available only for approved health-related research studies and access is project-specific and granted after review and approval by an RGE oversight committee and the University of Utah's IRB. This process allows researchers with approved protocols to use the data, a process that has proven effective and successful as evidenced by hundreds of approved studies that have relied on the UPDB.

Competing interests

We declare we have no competing interests.

Funding

Funding for this research was provided by the National Institutes of Health—National Institute of Aging, R01 AG022095 (Early Life Conditions, Survival and Health, Smith PI). We also thank the Pedigree and Population Resource of the Huntsman Cancer Institute, University of Utah for its role in supporting of the Utah Population Database (UPDB). We additionally acknowledge partial support for the UPDB through grant no. P30 CA2014 from the National Cancer Institute, University of Utah and from the University of Utah's Program in Personalized Health and Center for Clinical and Translational Science.