The value of a public health lens in dementia research
Seb Walsh (MBChB, MPhil, MFPH)
NIHR Doctoral Fellow in Public Health Medicine, University of Cambridge
06/02/2025
MELODEM
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Outline
Charles-Edward Winslow
(1877-1957)
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Public Health in 1920
“Public health is the science and the art of preventing disease, prolonging life, and promoting physical health and efficiency through organized community efforts for the sanitation of the environment, the control of community infections, the education of the individual in principles of personal hygiene, the organization of medical and nursing service for the early diagnosis and preventive treatment of disease, and the development of the social machinery which will ensure to every individual in the community a standard of living adequate for the maintenance of health.”
“Ignoring all minor specialties there must be at least the following seven types of highly qualified persons in this field:�
Winslow, 1920. Science
The Untilled Fields of Public Health
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Public Health – updates since 1920
#1
The burden of disease has changed
#2
The age structure has changed
Public Health – updates since 1920
Public Health – updates since 1920
Rose, 1985. International Journal of Epidemiology
Sick Individuals and Sick Populations
Geoffrey Rose
1926 - 1993
Determinants of individual cases
Vs. Determinants of incidence rate
#3
Risk exists on a continuum
Public Health – updates since 1920
Low risk
High risk
Proportion of the population
Individual-level approach
Population-level approach
Rose, 1992. Oxford Medical Publications
The Strategy of Preventive Medicine
“A large number of people at a small risk may give rise to more cases of disease than the small number who are at a high risk”
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Arapakis et al., 2020. BMJ Open
Dementia and disadvantage in the USA and England: population-based comparative study
Public Health – updates since 1920
#4
Inequality exists on a continuum
Adapted from: Adams et al., 2016. PLOS Medicine
Population interventions for diet and obesity
Public Health – updates since 1920
#5
Reach ≠ Equity
Fruit
Individuals’ Health State & Medical Needs (Dementia morbidity)
Distal Branches
Health Behaviours & Social Networks (Risk factor status)
Trunk
Social Determinants of Health (Population-level factors)
Proximal Branches
Neighbourhood & Community (Community assets)
Roots and Soil
Deep Societal Factors
(Sexism, Racism, Homophobia, Climate Change, Inequality)
Images generated by Google Gemini
BRAIN HEALTH
EQUALI-TREE!!
#6
Prevention at different levels
Research
Research Output
Enduring Impact
Research
Research Output
Research
Research Output
Research
Research Output
Research
Research Output
How do we reduce dementia morbidity by as much as possible?
Walsh et al., 2022. Lancet Neurology
The relevance of social and commercial determinants for neurological health
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Outline
DEMENTIA RISK
Livingston et al., 2024. The Lancet
Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission
Distal Branches
Health Behaviours & Social Networks
(Risk factor status)
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Most cases (70-80%) of future dementia will occur in people who are not in the high-risk group
Check your priors
Walsh et al., 2024. Alzheimer’s & Dementia
How many future dementia cases would be missed by a high-risk screening programme?
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‘Measures applied to populations, groups, areas, jurisdictions, or institutions with the aim of changing the social conditions (including cultural, physical, commercial, economic, environmental, occupational, or legislative conditions to make them less conducive to the development or maintenance of the modifiable lifecourse risk factors for dementia and/or more conducive to the development or maintenance of the modifiable lifecourse protective factors for dementia.’
Population-level approach to dementia risk reduction
Walsh et al., 2023. Public Health
What is a population-level approach to prevention, and how could we apply it to dementia risk reduction?
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Existing dementia prevention literature
Walsh et al., 2023. JPAD
Are Population-Level Approaches to Dementia Risk Reduction Under-Researched?
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Complex Evidence Review
Walsh et al., 2024. Lancet eClinicalMedicine
Population-level interventions for the primary prevention of dementia: a complex evidence review
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Evidence grading
High confidence | Comprehensive, consistent, and robust evidence, across a range of contexts |
Moderate confidence | Consistent and robust evidence, but only in a limited number of contexts |
Low confidence | Clear signal that the intervention can work, but lack of consistency or comprehensiveness |
Walsh et al., 2024. Lancet eClinicalMedicine
Population-level interventions for the primary prevention of dementia: a complex evidence review
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How
Walsh et al., 2024. Lancet eClinicalMedicine
Population-level interventions for the primary prevention of dementia: a complex evidence review
Risk Factor | Fiscal Interventions | Marketing/Advertising Interventions | Availability Interventions | Legislative Interventions |
Tobacco | (T1) Excise taxes on tobacco | (T2) Plain packaging, large health warnings�(T3) Comprehensive bans on advertising | (T4) Eliminate exposure to second-hand tobacco smoke in all public places |
|
Excess Alcohol | (A1) Excise taxes on alcohol�(A2) Minimum unit pricing | (A3) Comprehensive restrictions on advertising - including targeting young people | (A4) Restrictions on the physical availability of retailed alcohol (e.g. reduced hours of sale) |
|
Obesity | (O1) Taxation on unhealthy products e.g. sugar-sweetened beverages | (O2) Restrict marketing of unhealthy foods to children�(O3) Menu labelling in food service | (O4) Limit portion and package size to reduce energy intake (O5) Public food procurement policies to promote healthy diets | (O6) Reformulation policies for healthier food and beverage products |
Physical Inactivity |
|
| (P1) Urban and transport planning and design to provide compact neighbourhoods providing mixed-land use and connected networks for walking and cycling and equitable access to public open spaces | |
Hypertension |
|
| (H1) Public food procurement and service policies to reduce sodium intake | (H2) Reformulation policies for sodium reduction |
TBI |
|
|
| (Tr1) Mandate motorcycle helmets (all ages)�(Tr2) Mandate bicycle helmets (children) |
Low Education | (E1) Remove financial barriers to school attendance |
| (E2) Free lunches in primary schools, where there would otherwise be a lack of adequate food | (E3) Raise mandatory school leavers age |
Air Pollution |
|
| (Ai1) Replacement and maintenance programmes providing cleaner cooking stoves for those currently using biomass fuels on traditional stoves or open fires | (Ai2) Reduce density of traffic, including (e.g. low emission zones)�(Ai3) Postpone non-essential polluting activities on high-pollution days |
Hearing Impairment |
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| (He1) Reduce worksite noise through improving equipment where feasible; and provide adequate hearing protection, with regular monitoring | |
(Data from high-income countries only, low-/ middle-income countries, or both)
(T1) (A1) (A2) (O1)
Increase taxation on
tobacco, alcohol, and SSBs
(Ai2)
Measures to reduce traffic density e.g. LEZs
(He1)
Monitor and reduce worksite noise; and provide adequate hearing protection
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How
Walsh et al., 2024. Lancet eClinicalMedicine
Population-level interventions for the primary prevention of dementia: a complex evidence review
Intervention | Estimated effect size(s) | Key source(s) of evidence of effectiveness and effect estimate(s) | Key considerations | Further planning/ implementation guidance |
(He1) Worksites exceeding recognised noise thresholds should reduce noise through improving equipment where feasible, and should provide and mandate the use of adequate hearing protection, with regular monitoring | 60% reduction in occupationally-acquired hearing impairment��Avoidance of hearing loss OR 0.4 (95% CI 0.23, 0.69), at 5 years | Tikka et al., 2017. Interventions to prevent occupational noise‐induced hearing loss. Cochrane review | Worksites exceeding recognised thresholds (80 dB(A)) should provide and mandate the use of adequate hearing protection, with regular audiometric monitoring of those working in areas which continue to exceed thresholds despite installation of quieter equipment | WHO, 2018. Addressing the rising prevalence of hearing loss |
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How
Mukadam et al., 2024. Lancet Healthy Longevity
Benefits of population-level interventions for dementia risk factors: an economic modelling study for England
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Expansion of
morbidity?
Dhana et al., 2022. The BMJ
Healthy lifestyle and life expectancy with and without Alzheimer’s dementia
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A different way to think about risk
Walsh et al., 2023. Public Health
What is a population-level approach to prevention, and how could we apply it to dementia risk reduction?
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Outline
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Miracle Drugs
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Clinical Lens
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Clinical Lens – Effect size
Liu et al., 2021. Lancet Psychiatry
The need to show minimum clinically important differences in Alzheimer's disease trials
Phase III Trial Data
Between Group Differences
Lecanemab 0.45
Donanemab 0.68
Minimum Clinically Important Difference
Within Person Change
MCI 0.98
Mild AD 1.63
(CDR-SB)
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Clinical Lens – Effect size
Walsh et al., 2024. Alzheimer’s & Dementia
Considering challenges for the new Alzheimer’s drugs: clinical, population, and health system perspectives
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Clinical Lens - Concerns
Walsh et al., 2024. Alzheimer’s & Dementia
Considering challenges for the new Alzheimer’s drugs: clinical, population, and health system perspectives
| Donanemab | Placebo |
Any ARIA | 36.8% | 14.9% |
Symptomatic ARIA-E | 6.1% | 0.1% |
Large ARIA-H | 0.4% | 0.2% |
| Lecanemab | Placebo |
Any ARIA | 21.5% | 9.5% |
Symptomatic ARIA-E | 2.8% | 0% |
Symptomatic ARIA-H | 0.7% | 0.2% |
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Clinical Considerations
Walsh et al., 2024. Alzheimer’s & Dementia
Considering challenges for the new Alzheimer’s drugs: clinical, population, and health system perspectives
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Population Perspective
Walsh et al., 2024. Alzheimer’s & Dementia
Considering challenges for the new Alzheimer’s drugs: clinical, population, and health system perspectives
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Walsh et al., 2024. Alzheimer’s & Dementia
Considering challenges for the new Alzheimer’s drugs: clinical, population, and health system perspectives
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Pittock et al., 2023. Neurology
Eligibility for Anti-Amyloid Treatment in a Population-Based Study of Cognitive Aging
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Population Perspective
Walsh et al., 2024. Alzheimer’s & Dementia
Considering challenges for the new Alzheimer’s drugs: clinical, population, and health system perspectives
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Health System Perspective
Walsh et al., 2024. Alzheimer’s & Dementia
Considering challenges for the new Alzheimer’s drugs: clinical, population, and health system perspectives
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Health System Perspective
Walsh et al., 2024. Alzheimer’s & Dementia
Considering challenges for the new Alzheimer’s drugs: clinical, population, and health system perspectives
GP
Memory Clinic
Amyloid status
MRI head
Genotype (+ counselling)
70-95% ”fail” screening
Neurology
Weeks
Months
Months
“The cost-effectiveness estimate for donanemab is 5 to 6 times above what NICE normally considers an acceptable use of NHS resources.”
?
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Outline
Research
Research Output
Enduring Impact
Research
Research Output
Research
Research Output
Research
Research Output
Research
Research Output
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Final Thoughts
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With thanks to
Twitter: @seb_walsh
Contact: sjw261@cam.ac.uk