A recent study of data from nearly 4m people has showed that Gen-Xers have a greater chance of being diagnosed with cancer than the generation born before them, the Baby Boomers, although there is no clear reason why, say scientists.
Generation X was born between 1965 and 1980 and Baby Boomers between 1946 and 1964.
And, concludes the paper, published in JAMA Network Open, if current cancer trends continue, “cancer incidence in the US could remain unacceptably high for decades to come”.
The National Cancer Institute study authors said it was unclear what was driving the projected rise in rates of invasive cancer.
“Our study can’t speak to any particular cause,” lead author Philip Rosenberg, senior investigator in the institute’s biostatistics branch, told NPR. “It gives you boots-on-the-ground intelligence about what is happening. That’s where you go and look for clues about causes.”
Researchers believe early detection, obesity and sedentary lifestyles might explain some of the rise in cancer rates. Some research also points to pollutants, including the man-made chemicals known as PFAS, as possible culprits.
Rosenberg and his team used data from 3.8m people diagnosed with malignant cancer in America from 1992 until 2018 to compare cancer rates for members of Generation X and Baby Boomers.
He then ran modelling showing that when Gen-Xers turn 60 (starting in 2025), they are more likely to be diagnosed with invasive cancer than Boomers were at age 60.
In fact, cancer is more likely to hit Gen-Xers than any prior generation born between 1908 and 1964, the study’s projections found.
For decades, the news about cancer had largely been encouraging. Lung cancer rates were dropping, thanks to educational efforts about the harms of tobacco, and in women, of cervical cancer, while in men, liver, gallbladder and non-Hodgkin lymphoma, were also declining.
But these reductions have been overshadowed by an alarming rise in colorectal and other cancers in Gen-Xers and younger people.
The study’s models found increases in thyroid, kidney, rectal, colon cancers and leukaemia in both men and women. In women, it also found increases in uterine, pancreatic and ovarian cancers and in non-Hodgkin lymphoma. In men, the study also projected increases in prostate cancer.
Rosenberg was surprised by how many different types of cancer appeared to be rising at higher rates in Generation X members compared with Baby Boomers, and that projected increases in cancer rates would offset what he described as prior “very important and impressive declines” in cancers.
The increases for Generation X over Baby Boomers appeared in all racial and ethnic groups except Asian or Pacific Islander men, who were less likely to be diagnosed with cancer at 60 if they were Gen-Xers than Baby Boomers.
Douglas Corley, chief research officer for the Permanente Medical Group and a gastroenterologist in San Francisco, sees generational divisions for cancer trends as “somewhat artificial”, he said.
Over the past century, for example, the incidence of kidney cancer has increased steadily in young Americans.
“So it is not that being part of a particular more recent generation that puts you at risk,” he said. “It is not that one generation was necessarily exposed to something that others born one generation earlier were not. It is a year-by-year change.”
He believes the environment plays a role in the rising cancer rates.
Previous epidemiological studies point to pesticides, toxic chemicals and air pollutants as possible culprits, said Olga Naidenko, vice-president of science investigations at the Environmental Working Group, who was not involved in the research.
She said more should be done to reduce exposure to pollutants like PFAS, or “forever chemicals”, and pesticides.
“It is absolutely essential to invest in cancer-prevention research,” she said.
Corley also highlighted obesity, increasingly sedentary lifestyles and early cancer detection as part of the picture too.
He said it was worth noting that the latest study does not examine cancer death rates. For most cancers, earlier detection and better treatment have improved survival, he said.
Study author Rosenberg agrees. “We’re in a situation where America has made great progress, but there are also challenges preventing cancer.”
His data promised no reprieve for Millennials, the generation born after Gen-X.
“Is there anything that gives us hope that things will turn a corner for the Millennials?” he asked. “What we found is, no.”
Study details
Cancer incidence trends in successive social generations in the US
Philip Rosenberg, Adalberto Miranda-Filho.
Published in JAMA Network on 10 June 2024
Abstract
Importance
The incidence of some cancers in the US is increasing in younger age groups, but underlying trends in cancer patterns by birth year remain unclear.
Objective
To estimate cancer incidence trends in successive social generations.
Design, Setting, and Participants
In this cohort study, incident invasive cancers were ascertained from the Surveillance, Epidemiology, and End Results (SEER) programme’s 13-registry database (November 2020 submission, accessed August 14, 2023). Invasive cancers diagnosed at ages 35 to 84 years during 1992 to 2018 within 152 strata were defined by cancer site, sex, and race and ethnicity.
Exposure
Invasive cancer
Main Outcome and Measures
Stratum-specific semiparametric age-period-cohort (SAGE) models were fitted and incidence per 100 000 person-years at the reference age of 60 years was calculated for single-year birth cohorts from 1908 through 1983 (fitted cohort patterns [FCPs]). The FCPs and FCP incidence rate ratios (IRRs) were compared by site for Generation X (born between 1965 and 1980) and Baby Boomers (born between 1946 and 1964).
Results
A total of 3.8 million individuals with invasive cancer (51.0% male; 8.6% Asian or Pacific Islander, 9.5% Hispanic, 10.4% non-Hispanic black, and 71.5% non-Hispanic white) were included in the analysis. In Generation X vs Baby Boomers, FCP IRRs among women increased significantly for thyroid (2.76; 95% CI, 2.41-3.15), kidney (1.99; 95% CI, 1.70-2.32), rectal (1.84; 95% CI, 1.52-2.22), corpus uterine (1.75; 95% CI, 1.40-2.18), colon (1.56; 95% CI, 1.27-1.92), and pancreatic (1.39; 95% CI, 1.07-1.80) cancers; non-Hodgkins lymphoma (1.40; 95% CI, 1.08-1.82); and leukaemia (1.27; 95% CI, 1.03-1.58). Among men, IRRs increased for thyroid (2.16; 95% CI, 1.87-2.50), kidney (2.14; 95% CI, 1.86-2.46), rectal (1.80; 95% CI, 1.52-2.12), colon (1.60; 95% CI, 1.32-1.94), and prostate (1.25; 95% CI, 1.03-1.52) cancers and leukaemia (1.34; 95% CI, 1.08-1.66). Lung (IRR, 0.60; 95% CI, 0.50-0.72) and cervical (IRR, 0.71; 95% CI, 0.57-0.89) cancer incidence decreased among women, and lung (IRR, 0.51; 95% CI, 0.43-0.60), liver (IRR, 0.76; 95% CI, 0.63-0.91), and gallbladder (IRR, 0.85; 95% CI, 0.72-1.00) cancer and non-Hodgkins lymphoma (IRR, 0.75; 95% CI, 0.61-0.93) incidence decreased among men. For all cancers combined, FCPs were higher in Generation X than for Baby Boomers because gaining cancers numerically overtook falling cancers in all groups except Asian or Pacific Islander men.
Conclusions and Relevance
In this model-based cohort analysis of incident invasive cancer in the general population, decreases in lung and cervical cancers in Generation X may be offset by gains at other sites. Generation X may be experiencing larger per-capita increases in the incidence of leading cancers than any prior generation born in 1908 through 1964. On current trajectories, cancer incidence could remain high for decades.
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