Somewhere in a clinic corridor this morning, a family is reading the chart. Fourteen boxes, neatly arranged across a life: schooling in childhood, hearing and blood pressure and cholesterol in midlife, isolation and vision loss in later years. Forty-five percent, it says. Nearly half of dementia cases worldwide, theoretically preventable. It is one of the most quoted numbers in brain health, and it is doing a great deal of work. What the chart does not say is that the family standing in front of it may live in a country whose data barely shaped it.
That is the argument of a policy paper published in eBioMedicine on 25 September 2025, led by Cyprian Mostert of the Brain and Mind Institute at Aga Khan University, who is also affiliated with the Global Brain Health Institute at Trinity College Dublin, with co-authors including Chinedu Udeh-Momoh, Andrea Sylvia Winkler, Harris Eyre and Agustin Ibanez. It is important to be clear about what kind of document this is. It is a Personal View: an argument built from published literature, not a new study. Nobody was enrolled, nobody was followed, no new measurements were taken. The authors note that the datasets behind the global estimates were drawn largely from high-income country populations, and they propose four additions to the 2024 Lancet Commission's fourteen: poverty, wealth shocks, income inequality and viral infection, specifically HIV.
The paper's Table 1 is the spine of the case. For income inequality it gathers studies from Japan, the United Kingdom and a global analysis, averaging an effect size of 2.2 (range 1.3 to 3.0). For poverty, studies from the United States, South Africa, Pakistan and the United Kingdom, averaging 2.1 (1.5 to 3.1). For HIV, studies from the United States, Canada and Malawi, averaging 2.0 (1.5 to 3.1). Wealth shocks, the sudden loss of a large share of savings in later life, are represented by work from the United States, China and England, and carry the widest uncertainty of anything in the table. Every one of these is observational. They describe populations in which dementia was more common, not populations in which poverty was shown to cause it; and averaging effect sizes drawn from different countries, different designs and different definitions is a summary gesture, not a pooled analysis.
The part of the argument with the sharpest edge is about who the list describes. Of the fourteen factors in the 2024 report, the authors calculate that 57 percent are more prevalent in men. Dementia, meanwhile, falls more heavily on women worldwide. Add the four proposed factors and the arithmetic flips: ten of eighteen factors become more prevalent in women, which the paper describes as a 56 percent share of modifiable risk for women against 44 percent for men. If you design a national campaign around smoking, alcohol and head injury, you have built it around the half of the list where men dominate. If poverty, a vanished pension, the gradient of inequality and untreated HIV carry comparable weight, the campaign looks different, and so does the person it is aimed at. That reframing is now circulating in the wider field: a Perspective in Nature Aging published on 21 January 2026, proposing a syndemics framework for sex and gender risk in low and middle income countries, cites the paper among its references.
Then there is the headline number, and this is where a reader should slow down. The authors estimate that adding the four factors could raise the preventable share to about 65 percent, and in a conference abstract published in Alzheimer's and Dementia on 25 December 2025, Mostert puts the increment at roughly 20 percentage points. That figure is an illustrative projection from the assembled literature, not a population attributable fraction measured in a cohort. The 45 percent it builds on is itself theoretical. Gill Livingston, who chairs the Commission, described it in her own abstract published on 23 December 2025 as a theoretical potential reduction, and noted that the welcome fall in dementia risk seen in some high-income countries has been restricted to people with higher income and more education. On that last point, the critics and the Commission are not far apart.
For a family, none of this changes anything today. There is no action in this paper, nothing to start, nothing to stop, no test to ask for. What it changes is the address of the problem. If the authors are right, a meaningful slice of preventable dementia sits in cash transfers, pension protection, HIV treatment coverage and the blunt fact of household income, which are levers held by finance ministries and health systems rather than by individuals reading a chart in a corridor.