Science or Advocacy? The Global Rise of Policy Claims in Population Health Research (1990-2024)

Should original research routinely contain prominent policy claims, such as recommendations for policymakers or broad calls to action? Growing emphasis on "research impact" might be welcome but also have unintended consequences that include risks of overextrapolation, the blurring of roles between scientists and advocates, and potential erosion of scientific credibility. To inform this debate, we examined 45,807 abstracts from ten leading Epidemiology and Public Health journals (1990-2024). Using a large language model with human validation, we classified policy claims and mapped their prevalence by time, country, journal, field of study, and study design. Policy claims markedly increased in frequency from 17.6% in 1990-1999 to 35.8% in 2020-2024, with wide variation across countries (>40% in Italy and Australia vs <19% in Norway and Japan, 2020-2024) and journals (>60% in some vs <6% in others). Keywords linked to higher claim rates differed by topic and time: some corresponded to topics with clear causal evidence ("tobacco"), others to topics with more complex causal evidence and notable researcher advocacy ("health inequalities" and "COVID-19"). Claims were most common in qualitative or cross-sectional studies, and less common in cohort, quasi-experimental, or experimental studies. We argue that these patterns reflect a research culture increasingly oriented toward claiming policy relevance--and incentives that encourage attaching claims to single studies. Our findings raise questions about how scientists and journals balance evidence, advocacy, and credibility. Ensuring that policy claims remain commensurate with evidence will be central to build trust as policy impact continues to be incentivised. We discuss alternative ways for researchers and publishers to engage meaningfully with policy beyond attaching claims to individual studies, and share our data and scripts to catalyse further work in this area.