Disease exposure in infancy affects women’s reproductive outcomes and offspring health in southern Sweden 1905–2000. Van Dijk, Nilsson, Quaranta. Social Science and Medicine, 347 (116767). Paper here.

We investigated the long-term effects of peaking infectious disease, indicated by infant mortality peaks, in the year of birth. We were interested in the effects in mid-life, when mortality tends to be low and for which we can rarely study other health outcomes using historical data. We therefore took a closer look at women’s reproductive outcomes as in indicator of their health, using historical and contemporary obstetric records and demographic information. We found that, overall, exposed women had similar numbers of children as non-exposed women. However, women born in years with high infectious disease load gave birth to fewer boys, experienced more miscarriages, and experienced more (male) stillbirths. These results align with literature showing that male fetuses are more sensitive to mother’s health and overall conditions while she is pregnant. The exposed women gave birth to boys with a slightly higher birthweight so that the most robust boys may have been selected for survival. Overall, this evidence indicates that women exposed to infectious disease peaks early in life had a worse health in adulthood, and a reduced capacity to carry pregnancies to term.

Childhood neighborhoods and cause-specific adult mortality in Sweden 1939–2015. 2023. Hedefalk, van Dijk, Dribe. Health & Place, 84 (103137). Online (open access) here.

Today there is a large and growing social gradient in health but this has not always been the case. In this study we look into the social determinants of health for a cohort of children growing up in the town in Landskrona at a time that these social differences in health and mortality were smaller. We look into how mortality is affected by their social status and that of the children that they grew up with. We find that for men, adult mortality (age 40-69) is affected by their own social class and that of their peers while growing up. For women, that is not the case. Especially men’s preventable mortality is affected, pointing to lifestyle and behavioral factors as important mechanisms. Possibly, children growing up with peers from working-class families have higher alcohol and tobacco use in adulthood, resulting in a larger likelihood of mortality to behavior-related causes of death (lung cancer and COPD, injuries and external causes of death, alcohol-related diseases).

Increasing number of long-lived ancestors marks a decade of healthspan extension and healthier metabolomics profiles. 2023. Van den Berg, Rodriguez-Girondo, van Dijk, Slagboom, Beekman. Nature Communications, 14 (4518). Online (open access) here, summary on Twitter here and below.

Health and longevity are not individual accomplishments but cluster strongly in families. In this paper, we studied healthy lifespan and mortality over 26 years, among individuals with known parents and grandparents, in >2,000 families in the Netherlands (Leiden Longevity Study) and Sweden (SEDD). SEDD contains Swedish register data linked to historical records, and data from the Netherlands contain children of long-lived parents with a long-lived sibling (women >91y, men >89y) We selected people whose ancestors were the top survivors of their birth cohort.

We showed that an increasing number of long-lived ancestors associates with (1) decreasing mortality risk over the entire life course; (2) delay in cardiovascular and metabolic disease onset and multimorbidity from mid-life onward; (3) lower medication use; and (4) healthy metabolomics (chemical markers of the metabolism measured in blood) profile before disease onset. In the longest-lived families, the healthy lifespan was up to a decade longer. The results show that health and longevity benefits across the life course are not individual accomplishments but cluster strongly in families. The results further show a very strong link between longevity and healthspan.

The paper is the first paper from our externally funded projects by the Dutch Science Organization (PI van den Berg) and my project “An Age Old Advantage” funded by Riksbankens Jubileumsfond. We’re now continuing work looking into socio-behavioral and genetic mechanisms – stay tuned!

Exercise in a home for the elderly, Amsterdam, 1990. Archive Amsterdam, Busselmans.

Short Lives. The impact of parental death on early life mortality and height in the Netherlands 1850-1940. 2023. Quanjer, van Dijk, Rosenbaum-Feldbrugge (shared first authorship). Demography 60 (1): 255–279. Online-first here, summary on Twitter here.

We investigate how parental death in infancy, childhood and adolescence affects health using two distinct measures: mortality before age 20 and young adult height. Using two complementary indicators of health enables us to gain more insights into processes of selection and scarring of health. Employing nationally representative data for the Netherlands for the period 1850-1940, we analyze survival of roughly 36 thousand boys and girls using Cox proportional hazard models, and stature of more than 4,000 young adult men using linear regression models. Results show that parental loss, and particularly maternal loss, at an early age (0-1 and 1-5) was related to strongly increased mortality. At the same time, we do not identify an effect of parental loss at these ages on stature in young adulthood. For boys, maternal death between age 5-12 is strongly associated with shorter young adult height, while the association between paternal death and stature is generally weaker. Taken together, these results indicate that boys orphaned early in life, and whose health was likely to be affected most strongly, may not have survived to young adulthood.

Weert, Netherlands, October 1918. Spaarnestad Photo

Unequal excess mortality during the Spanish Flu pandemic in the Netherlands. Rijpma, van Dijk, Ruben Schalk, Zijdeman and Mourits. Economics and Human Biology. 407(101179), Available from the publisher here, summary on Twitter here.

In this paper, we explore the relation between occupational characteristics and excess mortality among men during the Spanish Flu pandemic in the Netherlands. By creating a new occupational coding for exposure to disease at work, we separate social status and occupational conditions for viral transmission. We estimate whether social position, regular interaction in the workplace, and working in an enclosed space affected excess mortality among men in the Netherlands in the autumn of 1918. We find some evidence that men with occupations that featured high levels of social contact had higher mortality in this period. Above all, however, we find a strong socioeconomic gradient to excess mortality among men during the Spanish Flu pandemic, even after accounting for exposure in the workplace.

Poor area in Amsterdam, 1913, Utrechts Archief

Kept in the Family: Remarriage, Siblings, and Consanguinity in the Netherlands. 2021. Van Dijk & Kok. Kept in the Family. Remarriage with Kin among Widows and Widowers in the Netherlands 1812 – 1937. Journal of Interdisciplinary History. 52 (3): 313–349. Available from the publisher here, from Lund University repository here.

Who remarries with their brother-in-law or sister-in-law after their partner’s death, even at a time that such a marriage was forbidden?

Widowhood involves many practical challenges next to the emotional impact of bereavement. Remarriage to a blood relative of a deceased spouse can often help a bereaved spouse to solve issues related to inheritance, child care, and comfort in a stressful period. A study of 15,540 widowers and 18,837 widows in the Dutch province of Zeeland—of whom about 8,000 men and 5,000 women eventually remarried—which uses genealogical data about their partners and the links family-reconstitution database, finds that the relatively high likelihood of farmers’ widows remarrying and doing so with kin may have been a strategy to prevent property from falling into the hands of other families. Notwithstanding that the attractiveness of a widow or widower could also be a factor in opportunities to remarry, older widows and widows with many young children, whose chances on the remarriage market tended to be poor, did not usually have such recourse to kin in remarriage.

Families in comparison: An individual-level comparison of life-course and family reconstructions between population and vital event registers. 2021. Van Dijk*, van den Berg*, Mourits*, Slagboom, Janssens,  & Mandemakers (* shared first authorship). Population Studies. 75(1): 91-110. Available with open access here.

How do different types of demographic sources affect the representation of life courses in databases? We compare two historical data sources: register-type data and linked vital event observations from civil certificates of birth, marriage and death, for the same individuals.

we compare family and life-course reconstructions for 495 individuals simultaneously present in two well-known Dutch data sets: LINKS, based on the Zeeland province’s full-population vital event registration data (passive registration), and the Historical Sample of the Netherlands (HSN), based on a national sample of birth certificates, with follow-up of individuals in population registers (active registration). We compare indicators of fertility, marriage, mortality, and occupational status, and conclude that reconstructions in the HSN and LINKS reflect each other well: LINKS provides more complete information on siblings and parents, whereas the HSN provides more complete life-course information. We conclude that life-course and family reconstructions based on linked passive registration of individuals constitute a reliable alternative to reconstructions based on active registration, if case selection is carefully considered.

Maternal Age and Child Reproductive Success. 2021. Van Dijk*, Van den Berg*, Mourits*. Historical Life Course Studies 10(3). (* shared first authorship). Available with open access here.

Are daughters of older mothers less fertile?

The human mutation rate is high and increases with chronological age. As female oocytes age, they become less functional, reducing female chances at successful reproduction. Increased oocyte mutation loads at advanced age may be passed on to offspring, decreasing fertility among daughters born to older mothers. In this paper we study the effects of maternal ageing on her daughter’s fertility, including total number of children, age at last birth, and neonatal mortality among her children. We study fertility histories of two generations of women from mutually exclusive families from a pre-demographic transition historical population in the Dutch province of Zeeland. Using mixed effect Poisson and linear models to take within family (sibling) relations into account, we show that among married daughters fertility is reduced for those who were born to mothers with an advanced maternal age, resulting in fewer children ever born and earlier ages at last birth. We do not find consistent evidence for effects on neonatal mortality. These results may indicate that women born to older mothers are negatively affected by their mothers’ increased age.

Longevity defined as top 10% survivors and beyond is transmitted as a quantitative genetic trait. 2019. Van den Berg, Rodriguez-Girondo, Van Dijk, Mourits, Janssens, Mandemakers, Beekman, Smith, Slagboom. Nature Communications, 10 (35). Available with open access here.

Survival to extreme ages clusters within families. We study 20,360 families containing index persons, their parents, siblings, spouses, and children, comprising 314,819 individuals from two large datasets, UPDB (US) and LINKS (Netherlands). Our analyses provide strong evidence that longevity is transmitted as a quantitative genetic trait among survivors up to the top 10% of their birth cohort. We show a survival advantage, mounting to 31%, for individuals with top 10% surviving first and second-degree relatives in both databases and across generations, even in the presence of non-longevous parents.

The Long Harm of Childhood: Childhood Exposure to Mortality and Subsequent Risk of Adult Mortality in Utah and the Netherlands. 2019. Van Dijk, Janssens, Smith. European Journal of Population 35(5): 851-871. Available with open access here.

How do early-life conditions affect adult mortality? Research has yielded mixed evidence about the influence of infant and child mortality in birth cohorts on adult health and mortality. Studies rarely consider the specific role of mortality within the family. We estimated how individuals’ exposure to mortality as a child is related to their adult mortality risk between ages 18 and 85 in two historical populations, Utah (USA) 1874–2015 and Zeeland (The Netherlands) 1812–1957. We examined these associations for early community-level exposure to infant and early (before sixth birthday) and late (before eighteenth birthday) childhood mortality as well as exposure during these ages to sibling deaths. We find that that exposure in childhood to community mortality and sibling deaths increases adult mortality rates. Effects of sibling mortality on adult all-cause mortality risk were stronger in Utah, where sibling deaths were less common in relation to Zeeland. Exposure to sibling death due to infection was related to the surviving siblings’ risk of adult mortality due to cardiovascular disease (relative risk: 1.06) and metabolic disease (relative risk: 1.42), primarily diabetes mellitus, a result consistent with an inflammatory immune response mechanism. We conclude that early-life conditions and exposure to mortality in early life, especially within families of origin, contribute to adult mortality.

Mortality Clustering in Families: A Review of the Literature. 2019. Van Dijk. Population Studies, 73, 1, 79-99. Available with open access here.

Research on early-life mortality in contemporary and historical populations has shown that infant and child mortality tend to cluster in a limited number of high-mortality families, a phenomenon known as ‘mortality clustering’. This paper is the first to review the literature on the role of the family in early-life mortality. Contemporary results, methodological and theoretical shortfalls, recent developments, and opportunities for future research are all discussed in this review. Four methodological approaches are distinguished: those based on sibling deaths, mother heterogeneity, thresholds, and excess deaths in populations. It has become clear from research to date that the death of an older child harms the survival chances of younger children in that family, and that fertility behaviour, earlier stillbirths, remarriages, and socio-economic status all explain mortality clustering to some extent.

Like mother, like daughter: Intergenerational transmission of infant mortality clustering in Zeeland 1833 – 1912. 2018. Van Dijk & Mandemakers. Historical Life Course Studies, 7(2), 28-46. Available with open access here.

The burden of infant mortality is not shared equally by all families, but clusters in high risk families. Earlier research has shown that the risk of early death among infants may at least partially be transmitted from grandmothers to mothers. We assess whether intergenerational transmission of mortality clustering occurred in Zeeland, and if so, whether it can be explained on the basis of the demographic characteristics of the families in which the infants were born. We find that mortality clustering is indeed transmitted from grandmothers to mothers, and that the socioeconomic status of the family, the survival of mothers and fathers, and the demographic characteristics of the family affected infant survival. However, they explain the heterogeneity in infant mortality at the level of the mother only partially.

With my fellow PhD candidates Rick Mourits and Niels van den Berg in Utah, during the three months we worked with the Utah Population Database (UPDB)