On Baby-Boomer Birth Certificates: A Clue to Cancer Risks?

Nick Mulcahy

October 19, 2016

Both parental occupation at birth and the socioeconomic status (SES) of the neighborhood that a baby is born into were associated with varying risks for certain cancers later in life, according to a new study of American baby boomers.

The study is novel because, although it is somewhat established that SES in early life may play a role in cancer risk in adulthood, parental occupation on the birth certificate has never been used in cancer epidemiology.

Researchers from the University of Utah, in Salt Lake City, and Rutgers University, in New Brunswick, New Jersey, now report that high occupational status of the parents, as indicated on the birth certificate, is associated with increased risk for breast and prostate cancers and melanoma.

They also found that location of the family home matters.

That is, in comparison with women from high SES neighborhoods, women born in neighborhoods with low SES faced much greater risks for invasive cervical cancer.

However, in those low SES neighborhoods, men faced lower risks for prostate cancer, and both sexes had a lower risk for melanoma.

Study results were published online September 21 in Cancer Epidemiology, Biomarkers and Prevention.

To arrive at these results, the investigators looked at the birth certificates of a cohort of 60,497 (47.9%) female and 65,838 (52.1%) male baby boomers born between 1945 and 1959 in two Utah counties to identify the parents' industry/occupation and thereby establish "individual-level" SES status.

The team also looked at average income of households in the families' census tracts at time of birth, thereby establishing "neighborhood-level" SES status.

The researchers determined adult cancer incidence through linkage to Utah Cancer Registry records. Mean follow-up time was about 34 years from age 18 years, and 91% of cohort members were alive at last follow-up.

Looking at cancer risk by SES quartile, they report that women in the lowest individual-level SES group had 17% lower risk for breast cancer than those in the highest SES group (hazard ratio [HR] = 0.83; 95% confidence interval [CI], 0.72 - 0.97).

Men in the lowest individual-level SES group had a 30% lower risk for prostate cancer than those in the highest SES group (HR = 0.70; 95% CI, 0.56 - 0.88).

For both men and women, adult offspring with the lowest individual-level SES had a melanoma risk that was 19% lower than those in the highest SES group (HR = 0.81; 95% CI, 0.67 - 0.98).

When looking at cancer risk by neighborhood-level SES status, the researchers found some distinct results, some of which supported the findings based on birth certificate-based data.

Women born into the lowest SES neighborhoods had a significantly increased risk that was 44% higher for invasive cervical cancer compared to women in the highest SES group (HR = 1.44; 95% CI, 1.12 - 1.85).

Neighborhood SES had effects similar to individual SES for melanoma and prostate cancer but was not associated with female breast cancer.

Overall, the investigators found no association with SES for pancreas, lung, and colon and rectal cancers.

"This study shows that early-life socioeconomic status, based on factors such as parental occupation at birth, may be associated with cancer risk in adulthood," said senior author Ken Smith, PhD, a population health researcher at Huntsman Cancer Institute of the University of Utah, in a press statement.

He continued: "Using this information, we may be able to identify individuals who are at higher risk for cancer due to socioeconomic status at birth."

But Dr Smith acknowledged that the association between SES and breast, cervical, and prostate cancer might reflect differences in participation in cancer screening ― namely, more affluent people are more likely to undergo screening and are therefore more likely to have cancers detected.

Medscape Medical News asked an expert not involved with the study to comment on that possibility. "The findings may simply confirm what we already know" about cancer risk, income levels, and screening, acknowledged Scarlett Lin Gomez, PhD, MPH, a research scientist at the Cancer Prevention Institute of California, in Fremont.

But she also championed the research. "I think the exciting novelty of the study is its ability to look at the two levels of childhood SES in association with cancer later in life," Dr Gomez told Medscape Medical News.

She explained that only a "few" studies have established the link for early-life SES and these later cancers, and "no studies have done it simultaneously for individual-level and neighborhood-level early-life SES."

Furthermore, Dr Gomez thinks that the SES associations may not simply be related to being able to afford cancer screenings but "may in fact indicate other factors present in early life, such as health behaviors or environmental exposures."

The study authors speculated a bit along those lines with regard to the melanoma findings.

"This is one of the first studies to report a trend of increasing melanoma incidence by early-life SES," they write.

"Given the known influence of exposure to UVA/UVB on melanoma risk, the results suggest that Utah residents with high SES had higher levels of sun exposure than low-SES residents," the authors comment, adding that SES-related exposure patterns might include intermittent intense sun exposure while skiing as well as traveling to sunnier climates during winter.

The new study did not include a list of occupations/industries and their related socioeconomic rank. The study's lead author had not responded to a request for that information by the time this article had posted.

Funding for this study was provided by the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program. Further funding was provided by the Huntsman Cancer Foundation.

Cancer Epidemiol Biomarkers Prev. Published online September 21, 2016. Abstract

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