The incidence of childhood cancer is as much as 15% higher in the least marginalized neighborhoods than in the most marginalized areas, a study suggests.

The findings of this population-based, cross-sectional study were driven mainly by hematologic and other solid cancer types. Childhood cancer is the second leading cause of death among children in Canada.

“These results definitely challenge our assumptions that lower-income patients might be exposed to environmental factors that could put them at greater risk for childhood cancer,” Maria Chiu, PhD, senior scientist at the Pediatric Oncology Group of Ontario (POGO) and associate professor at the University of Toronto, Toronto, told Medscape News Canada.

The data were published on July 15 in JAMA Network Open. 

Building on Previous Studies

While socioeconomic factors were examined in earlier studies of cancer survival rates, little is known about the association between socioeconomic factors and cancer incidence, according to Chiu.

“This research built on previous studies that have been done in North America, Europe, and elsewhere in the world, but the evidence has been mixed,” she said. “Many of those studies focused only on specific cancers, which makes them limited. They also looked at only one measure of socioeconomic status, such as income or education, but no one had taken a comprehensive view of all the various measures of marginalization to pinpoint the prevailing factor that was closely associated with incidence of childhood cancer.”

The study included approximately 2.3 million children aged 0-14 years and 9063 pediatric cancer cases that were diagnosed in Ontario between 1999 and 2023. The researchers linked data from the population-based POGO Networked Information System cancer registry with Statistics Canada’s postal code and Ontario Marginalization Index (ON-Marg) databases to identify the patients with pediatric cancer. They analyzed the data from October 2025 to February 2026.

The study’s main outcomes were crude and age-standardized incidence rates for each ON-Marg dimension. The researchers estimated incidence rate ratios using multivariable Poisson regression models adjusted for age, sex, and diagnosis period for the overall population and stratified by cancer subtype. These subtypes included leukemia and lymphoma, central nervous system tumors, and other non-central nervous system solid tumors.

The ON-Marg provides a composite measure of social disadvantage that includes the following four factors: material resources, households and dwellings, age and labor force participation, and racialized and newcomer populations.

The greatest proportions of incident cancer cases were observed among children living in the least marginalized ON-Marg quintile of material resources (2171 [24.0%]), households and dwellings (2558 [28.2%]), and age and labor force participation (2938 [32.4%]).

Immunology and Delayed Infection

This epidemiologic study was designed to report what happened, not the reasons why, Chiu emphasized. It was not a cause-and-effect analysis. One hypothesis is that immunology and delayed infection influenced the study results. “We found that certain factors associated with affluence, and perhaps even population-level factors like older parental age, people waiting longer to have children, pregnancy- or birth-related factors, and differences in early life infection patterns, may help shape how a child’s immune system develops. These elements should be explored in future studies,” said Chiu.

Experts point to exposure to daycare as a possible reason for lower cancer incidence among children from lower-income families. “We found that lower-income parents were more likely to send their children to daycare facilities in large group settings. As a result, [the children are] more likely to have been exposed to common childhood infections early on, which helps prime the immune system for the future,” explained Chiu.

“The study findings aren’t surprising,” Eric Bouffet, MD, PhD, professor emeritus of pediatrics at the University of Toronto and director of the pediatric neuro-oncology program at the Hospital for Sick Children, told Medscape News Canada. “It’s already been shown that the incidence and prevalence of leukemia are higher in children who have less exposure to daycare.

“The big question remains whether we can draw any lesson from this, regarding prevention or early diagnosis. I don’t think so. The message here is, ‘Don’t think that if you have a higher income, you can protect your child by not putting them in the daycare system.’ In fact, as a global message for the government, these findings provide a strong rationale to support daycare funding because it’s a win-win situation. There is a social benefit to this, but here there is a demonstration that there may also be a healthcare benefit in terms of immunology,” Bouffet concluded.

This study was supported by the Pediatric Oncology Group of Ontario, which is funded by the Ontario Ministry of Health and philanthropic donors. Chiu and Bouffet reported no relevant financial relationships. 

Evra Taylor is a widely published freelance medical writer and reporter with 20 years’ experience covering a broad range of therapeutic sectors, including family health, cardiology, psychiatry, ophthalmology, and dermatology.