There have been countless reports recently warning of the ‘explosion’ of various forms of cancer among young(ish) people. Prompted by research documenting the rising rate of cancer diagnoses among people under 50, media outlets and politicians, from the Guardian and the BBC to RFK Jr, have been eagerly speculating and fearmongering about the likely causes.
What’s often missing from this discussion, however, is the crucial context of year-on-year improvements in cancer incidence and mortality, and substantial declines in the age-standardised death rates. Among people of the same ages, the cancer mortality risk has fallen by about one-third since 1990.
Collectively, the evidence suggests that true increases in early-onset cancers, especially gastrointestinal cancers and breast cancer, are real, but they still account for only around 10 per cent of all cancer diagnoses. The remaining 90 per cent occur in people over 50. Early-onset cancers are certainly distressing, not least because of the emotional toll, protracted treatment and associated side effects like infertility. But their public-health significance depends not just on how serious they are, but also on how many people they affect.
Plenty of causes have been proposed for the uptick, but the usual suspects dominate: rising levels of obesity, excess alcohol consumption, lack of exercise and poor sleep. In the US, obesity roughly doubled from the early 1990s to 2017. That timing makes for an awkward fit: today’s 30- to 50-year-olds were largely too old to have grown up during the peak of that surge, and most cancers – especially solid tumours like those in the gastrointestinal tract – have long latency periods. Even if we were to assume obesity is the cause, that still leaves many other early-onset cancers unaccounted for. Gastrointestinal cancer represents only about 10 per cent of the increasing cancer incidence. The rest includes cancers like thyroid, testicular and melanoma, which have no strong lifestyle links.
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