Fertility and Well-Being

At a Glance Projects Publications Team


Consequences of Sibling Group Structure

Conducted by Mikko Myrskylä; Susie Lee, Kieron Barclay; in Collaboration with Anna Baranowska-Rataj (Umeå University, Sweden), Martin Kolk, Martin Hällsten (both: Stockholm University, Sweden), Dalton Conley (Princeton University, USA)

Detailed Description

The focus of this project is to examine how fertility decisions made by parents, which affect sibling group structure and the early-life conditions experienced within the family, affect a range of health, educational, and socioeconomic outcomes for children, using registry or register-like data.

Previous research suggests that short birth-spacing increases the risk of poor perinatal and poor long-term socioeconomic outcomes. Existing research also shows that children without siblings as well as later-born siblings in multi-child sibling groups have worse long-term socioeconomic and health outcomes. As a result, it is important to understand how these various factors influence offspring outcomes.

Two of our new works addressed the importance of family size during childhood for health and mortality, using Swedish population registers. We found overall lower health and survival rates among only children compared with those who have one or two siblings. As yet, only children without half-siblings were consistently healthier than those with half-siblings, suggesting that parental disruption confers additional disadvantages. In another study, we used a novel approach – cousin fixed-effects – to study whether birth order in the parental generation influences the educational attainment of their children. The method compares cousins who share the same biological grandparents and therefore adjusts for unobserved factors in the extended family.

We also expanded our previous works on the health implications of birth intervals. Revisiting the question of long-term consequences of short birth intervals and using the Utah Population Database, we found that not even the very shortest birth intervals are negatively associated with educational or occupational outcomes or with long-term mortality. In another work, we found that in a high-income country such as contemporary Sweden, neither short nor long birth intervals seem to have a negative effect on birth outcomes such as preterm birth, low birth weight; nor do birth intervals affect the probability of hospitalization during childhood. These findings challenge much of the previous work produced in similar high-income contexts, encouraging more research to be done to ascertain the long-term implications of birth intervals on offspring health.

Research Keywords:

Fertility Development, Health Care, Public Health, Medicine, and Epidemiology


Dierker, P.; Diewald, M.:
MPIDR Working Paper WP-2023-004. (2023)    
Keenan, K.; Barclay, K. J.; Goisis, A.:
Population Studies 77:1, 71–90. (2023)    
Howe, L. J.; Nivard, M. G.; Morris, T. T.; Hansen, A. F.; Rasheed, H.; Cho, Y.; Chittoor, G.; Ahlskog, R.; Lind, P. A.; Palviainen, T.; van der Zee, M. D.; Cheesman, R.; Mangino, M.; Wang, Y.; Li, S.; Klaric, L.; Ratliff, S. M.; Bielak, L. F.; Nygaard, M.; Giannelis, A.; Willoughby, E. A.; Reynolds, C. A.; Balbona, J. V.; Andreassen, O. A.; Ask, H.; Baras, A.; Bauer, C. R.; Boomsma, D. I.; Campbell, A.; Campbell, H.; Chen, Z.; Christofidou, P.; Corfield, E.; Dahm, C. C.; Dokuru, D. R.; Evans, L. M.; de Geus, E. J. C.; Giddaluru, S.; Gordon, S. D.; Harden, K. P.; Hill, W. D.; Hughes, A.; Kerr, S. M.; Kim, Y.; Kweon, H.; Latvala, A.; Lawlor, D. A.; Li, L.; Lin, K.; Magnus, P.; Magnusson, P. K. E.; Mallard, T. T.; Martikainen, P.; Mills, M. C.; Njølstad, P. R.; Overton, J. D.; Pedersen, N. L.; Porteous, D. J.; Reid, J.; Silventoinen, K.; Southey, M. C.; Stoltenberg, C.; Tucker-Drob, E. M.; Wright, M. J.; Social Science Genetic Association Consortium within Family Consortium; Hewitt, J. K.; Keller, M. C.; Stallings, M. C.; Lee, J. J.; Christensen, K.; Kardia, S. L. R.; Peyser, P. A.; Smith, J. A.; Wilson, J. F.; Hopper, J. L.; Hägg, S.; Spector, T. D.; Pingault, J.; Plomin, R.; Havdahl, A.; Bartels, M.; Martin, N. G.; Oskarsson, S.; Justice, A. E.; Millwood, I. Y.; Hveem, K.; Naess, Ø.; Willer, C. J.; Åsvold, B. O.; Koellinger, P. D.; Kaprio, J.; Medland, S. E.; Walters, R. G.; Benjamin, D. J.; Turley, P.; Evans, D. M.; Smith, G. D.; Hayward, C.; Brumpton, B.; Hemani, G.; Davies, N. M.:
Nature Genetics 54:5, 581–592. (2022)    
Barclay, K. J.; Lyngstad, T. H.; Conley, D.:
European Sociological Review 37:4, 607–625. (2021)    
Barclay, K. J.; Baranowska-Rataj, A.; Kolk, M.; Ivarsson, A.:
Population Studies 74:3, 363–378. (2020)    
Gabay-Egozi, L.; Grieger, L.; Nitsche, N.:
MPIDR Working Paper WP-2020-031. (2020)    
Keenan, K.; Barclay, K. J.; Goisis, A.:
MPIDR Working Paper WP-2020-004. (2020)    
Spilerman, S.; Barclay, K. J.:
MPIDR Working Paper WP-2020-017. (2020)    
Molitoris, J.; Barclay, K. J.; Kolk, M.:
Demography 56:4, 1349–1370. (2019)    
Barclay, K. J.:
Research in Social Stratification and Mobility 54, 56–65. (2018)    
Barclay, K. J.; Kolk, M.:
Demography 55:3, 929–955. (2018)    
Baranowska-Rataj, A.; Barclay, K. J.; Kolk, M.:
Population Studies 71:1, 43–63. (2017)    
Barclay, K. J.; Hällsten, M.; Myrskylä, M.:
Social Forces 96:2, 629–660. (2017)    
Barclay, K. J.; Myrskylä, M.; Tynelius, P.; Berglind, D.; Rasmussen, F.:
Drug and Alcohol Dependence 167, 15–22. (2016)    
Barclay, K. J.; Myrskylä, M.:
Social Science and Medicine 123, 141–148. (2014)    
The Max Planck Institute for Demographic Research (MPIDR) in Rostock is one of the leading demographic research centers in the world. It's part of the Max Planck Society, the internationally renowned German research society.