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Disentangling climate hazards from demographic change in climate–health projections

Nature Medicine (2026)Cite this article

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Projections of the future impacts of climate change warn of rapidly growing burdens on public health in the coming century1,2,3. However, many of these estimates conflate three expected, yet distinct, drivers of future health risk: (1) changes in climate hazards (such as increased frequency of heat waves); (2) changes in the total number of people exposed (population growth); and (3) changes in the underlying vulnerability of people exposed (that is, increased population aging). When these drivers are not separated, projected impacts of climate change can be overstated, understated, or simply misattributed, undermining both scientific clarity and effective adaptation planning. The field of climate epidemiology needs to move beyond projections that ignore or obscure the influence of population dynamics. Clear attribution is central to both credible science and sound policy.

Global warming is increasing the frequency, intensity and geographical spread of many hazards3. At the same time, populations worldwide are both growing and aging, with older adults making up an increasingly large share of many communities4. Older adults are disproportionately vulnerable to health impacts from a range of environmental and climate exposures3,5, including heat, wildfire smoke and natural disasters. These demographic shifts are substantial and are likely to raise future environmental health burdens, even if climate hazards were to hold steady, by increasing overall population vulnerability.

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Authors and Affiliations

  1. Urban Health Collaborative, Dornsife School of Public Health, Drexel University, Philadelphia, PA, USA

    Josiah L. Kephart & Usama Bilal

  2. Department of Environmental and Occupational Health, Dornsife School of Public Health, Drexel University, Philadelphia, PA, USA

    Josiah L. Kephart

  3. Department of Epidemiology and Biostatistics, Dornsife School of Public Health, Drexel University, Philadelphia, PA, USA

    Usama Bilal

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  1. Josiah L. Kephart
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  2. Usama Bilal
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Correspondence to Josiah L. Kephart.

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Kephart, J.L., Bilal, U. Disentangling climate hazards from demographic change in climate–health projections. Nat Med (2026). https://doi.org/10.1038/s41591-025-04120-9

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