The bottom line: In a Danish population-register study, grandchildren of families containing multiple exceptionally long-lived siblings had lower infant mortality and lower risks of several adverse birth outcomes than matched members of the general population. The advantages were weaker and less consistent one generation later. The observational findings suggest that some features associated with exceptional longevity may be visible near the start of life, but they cannot show that longevity genes caused those differences.
Evidence at a glance
- Study type: Four-generation matched cohort study using Danish national registers.
- Families: 659 longevity-enriched families, initially selected because at least two siblings had survived to age 88 or older. Almost all qualifying sibling pairs eventually reached at least 90.
- Births analyzed: 5,637 grandchildren and 14,908 great-grandchildren of the long-lived sibling generation, compared with 41,090 matched births from the general population.
- Main finding: Grandchildren had about half the rate of infant mortality seen in matched controls and lower risks of preterm birth, being small for gestational age and neonatal respiratory disorders.
- Evidence level: Observational population research. It identifies family-level associations and cannot separate genetic effects from all shared environmental, behavioral or socioeconomic influences.
Looking for longevity before aging begins
Research on exceptional longevity usually starts late in life. Scientists compare centenarians or their adult children with people from the general population and look for differences in disease, behavior or biology.
The Danish study asked a more unusual question: do health advantages in long-lived families appear as early as pregnancy, birth and infancy?
The idea does not mean that lifespan is fixed at birth. Rather, it comes from a life-course view of health. The biology and environment of early development can influence later vulnerability, while families can also transmit genes, habits, resources and social conditions across generations.
How the families were identified
The researchers began with 659 Danish families assembled through three longevity studies. Each family included a sibling group in which at least two people had reached age 88 and were still alive when recruited between 2004 and 2009. Eventually, 99.5% of these qualifying sibling pairs included two people who reached at least 90.
Interviews and Denmark’s Civil Registration System linked those long-lived siblings, called the G1 generation, to their children, grandchildren and great-grandchildren. The researchers then connected family records to national birth, hospital, education and income registers.
The analysis covered live births from 1973 through 2018. Each descendant birth was matched with two births from the general population according to sex, birth year and season, the mother’s birth year and parity, and whether the mother was born in Denmark.
The final sample contained 61,635 births: 5,637 grandchildren, designated G3, and 14,908 great-grandchildren, designated G4, from longevity-enriched families, plus 41,090 matched controls.
The clearest advantage appeared in the grandchildren
Among G3 grandchildren, the rate of death during the first year of life was about half that of matched controls. The hazard ratio was 0.53, with a 95% confidence interval from 0.36 to 0.77. In absolute terms, cumulative survival at one year was 0.41 percentage points higher.
The largest separation occurred during the first month after birth, pointing to the neonatal period rather than the rest of infancy as the main source of the difference.
G3 grandchildren also had lower odds of several adverse outcomes. After correction for multiple statistical tests, the clearest associations were for preterm birth, being small for gestational age and neonatal respiratory disorders. The absolute risk differences were modest, ranging from about 1.4 to 2.5 percentage points for those outcomes, but they pointed in a consistent favorable direction.
The great-grandchildren told a more cautious story. Their infant-mortality hazard ratio was 0.90, with a confidence interval from 0.70 to 1.17, a result compatible with anything from a moderate advantage to no difference. Some neonatal outcomes remained slightly more favorable, including being small for gestational age, but the overall pattern was weaker and less consistent.
Why the weaker fourth-generation signal matters
The decline in the association with greater distance from the long-lived siblings is one of the study’s most informative observations. The researchers tested whether it could simply reflect improving neonatal care over time, which might allow the general population to catch up. In analyses restricted to overlapping birth years, the difference between the two descendant generations remained.
The authors interpret this as dilution of a bundle of protective family factors across generations. That bundle could include inherited variants, parental health, prenatal conditions, behavior, partner selection and shared social environments. The design cannot assign the pattern to any single component.
Similar infant-survival associations appeared whether the mother or father came from the longevity-enriched family. That weakens a simple explanation based only on maternal physiology, but it does not prove a genetic mechanism. Paternal and maternal lines can transmit environmental and social influences as well as DNA.
Genes are only one possible explanation
Exceptional longevity tends to cluster in families more strongly than ordinary variation in lifespan, making genetic protection plausible. A child may inherit combinations of variants that support cardiovascular, metabolic, immune or cellular resilience.
Yet family resemblance is broader than genetics. Relatives often share diet, smoking patterns, healthcare access, housing, stress exposures and expectations about health. People also tend to choose partners with partly similar education, behavior and social background, a process known as assortative mating.
The study found lower rates of smoking during pregnancy among mothers in both descendant generations. Parents in the longevity-enriched families also showed some socioeconomic advantages. Adjusting for measured education, income and marital status changed the main estimates very little, suggesting that those recorded factors did not fully account for the results.
That does not remove confounding. The registers captured only a limited set of socioeconomic and behavioral measures. They could not fully measure nutrition, detailed smoking histories, healthcare use, neighborhood conditions, family support, parental health or many other influences that might travel through families.
What the study can and cannot establish
National registers are a major strength because they cover large populations with long follow-up and reduce reliance on memory. Matching also made the comparison groups similar on several important birth and maternal characteristics.
But this was not a randomized experiment, and researchers did not manipulate genes or family environments. The study can establish that early-life advantages were associated with descent from these longevity-enriched families. It cannot establish that longevity genes caused the differences, that healthier infancy caused exceptional longevity, or that any individual child was destined for a long life.
The G4 generation is also still too young for researchers to know whether its weaker early-life pattern will correspond to adult health or lifespan. Smoking information was incomplete for much of the G3 generation, and the study did not cover every developmental milestone or exposure.
A developmental clue, not a longevity forecast
The results fit the developmental origins of health and disease framework, which studies how conditions during fetal life and infancy can shape later physiology. Better early growth, fewer respiratory problems and improved neonatal survival could be early expressions of the same protective family context that later supports healthy aging.
The direction may also run the other way. Families with healthier adults may create healthier pregnancies and early environments. Both processes could operate together, along with inherited biology.
The Lifespan Brief assessment
The study extends the story of exceptional longevity toward the beginning of life. In these Danish families, the clearest health advantage was not limited to old age or even adulthood. It was visible in birth outcomes and infant survival among grandchildren of exceptionally long-lived sibling groups.
The weakening in the next generation argues against a simple longevity-gene narrative. The more plausible interpretation is a changing mixture of genetic, parental, behavioral, environmental and socioeconomic influences. Following these families as younger generations age, and adding direct genetic and biological measurements, will be necessary to understand which parts of that mixture matter most.
Primary sources
Developmental origins of exceptional health and survival: a four-generation family cohort study, Nature Communications, 2026.
University of Southern Denmark research unit overview: epidemiology across the life course.
This article is for general information and is not personal medical advice.