Objective To assess whether changes in behavioural risk factors could explain rising cancer incidence in younger adults in England, and to evaluate the extent to which established and suspected risk factors contribute to these trendsMethods and analysis Cancer incidence data from national registries (2001–2019) for 22 sites in women and 21 in men identified cancers with increasing incidence in adults aged 20–49 years. Trends in smoking, alcohol, diet, body mass index (BMI) and physical inactivity were examined using national health surveys. Annual percentage changes (APCs) quantified trends by age and sex. Population attributable fractions (PAFs) estimated the proportion of cancers attributable to risk factors and disaggregated attributable from non-attributable incidence rates.Results Eleven cancer sites (three female-specific) with established behavioural risk factors showed rising incidence in younger adults. Similar trends were observed in older adults, except for colorectal and ovarian cancer, which increased only in younger adults. For some cancers, incidence increased more rapidly in younger than older adults. PAFs for younger adults ranged from 7% to 65% depending on cancer type. All risk factors except obesity showed stable or declining prevalence. For BMI-related cancers, both BMI-attributable and BMI-non-attributable incidence increased, though more slowly for the latter. For example, BMI-attributable colorectal cancer in younger women increased from 0.9 to 1.6 per 100 000 (APC 4.3%), while non-attributable rates rose from 6.4 to 9.6 (APC 3.2%).Conclusions Behavioural risk factors account for a substantial share of cancer burden but, apart from BMI, are unlikely to explain the rising incidence in younger adults. The present findings underscore the urgent need to investigate emerging risk factors, while strengthening prevention efforts targeting known factors across all ages.
Gunter et al. (2026) studied this question.