Siblings of Children with Cancer Show No Lasting Drop in School Grades, Swedish Register Study Finds

When a child is diagnosed with cancer, the entire family's life is upended: hospital stays, treatment schedules and emotional strain can crowd out everyday routines, including homework and school attendance. A question that has received surprisingly little research attention is whether the healthy brothers and sisters of these children pay an academic price. A new nationwide register-based cohort study from Sweden, published in Frontiers in Public Health, set out to answer that question by following thousands of siblings across decades of school records, and its central finding is broadly reassuring: having a brother or sister with childhood cancer was not associated with poorer school grades overall.

The research team, led by Moa Carlbaum of Lund University with colleagues at Lund, the Icahn School of Medicine at Mount Sinai, Shimane University and the University of Macau, exploited Sweden's comprehensive national registers, which link medical, demographic and educational data at the individual level. The study population consisted of 2,148 cancer-free siblings, born between 1972 and 2002, of children diagnosed with cancer between 1997 and 2016. Each of these siblings was compared with a pool of 7,571 matched individuals drawn from the general population.

Matching was deliberately stringent: comparison subjects shared the same type of sibling relationship, full or half sibling, the same country of birth, Sweden or abroad, the same sex, the same birth year and birth month, and even the same parental education levels, since the cancer-affected child's birth year and month and the mother's and father's highest education were also matched. This design helps ensure that any difference in school outcomes is less likely to reflect family background or demographic confounding. The outcome measure was straightforward but standardized across decades.

School grades were available between 1989 and 2018, and the researchers defined poor academic performance as falling in the lowest 25th percentile of grades within each year, a within-year cutoff that partially adjusts for differences in grading systems and cohorts over the long study window. Using conditional logistic regression, a statistical method suited to matched case-control style comparisons, the team calculated odds ratios with 95 percent confidence intervals for poor performance among siblings of children with cancer versus matched controls. The headline result was essentially null.

Individuals with a sibling diagnosed with childhood cancer had an odds ratio of 1.04 for poor academic performance, with a 95 percent confidence interval of 0.92 to 1.17. Because that interval comfortably includes 1.0, the data provide no evidence of a statistically significant association between a sibling's cancer diagnosis and worse school grades. In practical terms, on average, the healthy siblings in this large national cohort performed academically much like their carefully matched peers.

Yet the study did contain a signal worth flagging, one the authors themselves describe as exploratory and hypothesis-generating. When the analysis was restricted to siblings whose grades were assessed in the same year as the cancer diagnosis, the odds ratio for poor academic performance rose numerically to 1.32, with a confidence interval of 0.97 to 1.80. That estimate did not reach conventional statistical significance, but the interval sits just above the null at its lower bound, hinting at a possible short-term effect concentrated around the period of diagnosis.

The authors are careful about interpretation. They conclude that no significant association was found between a childhood cancer diagnosis in the family and academic achievement in healthy siblings, while emphasizing that the question needs further study with larger sample sizes. The same-year estimate, they note, should be examined in larger studies rather than treated as an established effect.

The study's strengths are considerable. Nationwide register coverage removes the selection biases that plague smaller, clinic-based samples, and the matching on sibling type, sex, birth timing, country of birth and parental education addresses many of the socioeconomic and familial factors that usually confound educational outcomes. For clinicians, educators and families, the findings offer a measured message.

The long-term academic outlook for siblings of children with cancer in this Swedish cohort appears similar to that of comparable peers, which challenges assumptions of pervasive, lasting educational harm.

Subject of Research: Academic performance of cancer-free siblings of children diagnosed with childhood cancer in Sweden

Article Title: Academic achievements among siblings of children with cancer in Sweden: a nationwide register-based cohort study

Article References: Carlbaum, M., Liu, Y., Sundquist, J., Sundquist, K., & Ji, J. (2026). Academic achievements among siblings of children with cancer in Sweden: a nationwide register-based cohort study. Frontiers in Public Health, 14, Article 1894774. https://doi.org/10.3389/fpubh.2026.1894774

Image Credits: AI Generated

DOI: 10.3389/fpubh.2026.1894774

Keywords: childhood cancer, siblings, academic performance, school grades, register-based cohort study, Sweden, family impact, conditional logistic regression, public health, pediatric oncology, Academic, achievements