Study identifies powerful opportunity to act on dementia prevention

Posted on: 17 November 2025

The study was published in the international journal BMJ Open.

Dementia remains one of the leading causes of disability and dependency in older adults worldwide, and its prevalence is rising rapidly. This 12-year longitudinal study, involving over 8,000 participants, provides the most detailed national picture to date of how modifiable risk factors (behaviours or exposures that can be changed or controlled to lower the risk of developing diseases) contribute to cognitive decline in later life.

The study explores the prevalence of the 14 modifiable dementia risk factors highlighted in the 2024 Lancet Commission report on Dementia Prevention, Intervention and Care. These risk factors are lower educational attainment, hearing loss, high cholesterol, high blood pressure, physical inactivity, diabetes, social isolation, excessive alcohol consumption, air pollution, smoking, obesity, traumatic brain injury, depression, and visual loss.

TILDA researchers reveal that more than 70% of adults aged 50 years and older in Ireland live with at least four modifiable risk factors for dementia, representing over half a million people nationwide. Furthermore, nearly one in four older adults experienced moderate or severe decline in cognitive performance over the study period.

Based on the Lancet Commission’s estimate that up to 45% of dementia cases are preventable through addressing modifiable risk factors. Incredibly, TILDA’s findings suggest that more than 100,000 cases of dementia could potentially have been prevented during the 12-year follow-up period. A proactive and standardised approach to identify and manage these risk factors through the development of dedicated brain health services could have a profound impact on individuals, healthcare systems, and Irish society as a whole.

Key Findings from the study

• Over 70% of adults aged 50 years or older in Ireland had at least four treatable risk factors for dementia.
• Over 500,000 older people in Ireland had at least four treatable risk factors for dementia at all three time points across the 12-year follow-up period. To put this in perspective, this represents nearly half of Ireland’s estimated 1.1 million community-dwelling adults aged 50 years or older, based on 2022 census data.
• Almost 225,000 people or one quarter of the population of older people in Ireland experienced moderate or severe decline in cognitive performance during the follow-up period. Those with severe decline in cognitive performance had higher numbers of modifiable risk factors compared to those with mild / moderate decline.
• The TILDA study demonstrates under-treatment of several dementia risk factors:
  • Hearing loss: Less than one third of older people with hearing loss reported using hearing aids either some or all of the time.
  • Depression: Access to psychological interventions remained notably low, with only 3% reporting engagement in such therapies.
  • Treatment and control of key cardiovascular risk factors including diabetes, high blood pressure and high cholesterol were found to be particularly inadequate.

Lead author Dr Caoimhe McGarvey, Research Fellow at TILDA and Specialist Registrar in Geriatric Medicine at St James’s Hospital Dublin, commented:

“This study identifies a powerful opportunity to act on dementia prevention. Many of the risk factors, such as such as hypertension, high cholesterol, physical inactivity and hearing loss—are modifiable through straightforward, cost-effective interventions. By placing renewed emphasis on brain health throughout the life course and addressing these risks systematically, we have the potential to significantly delay or even prevent the onset of dementia for many individuals.”

Senior author Dr Robert Briggs, Consultant Geriatrician at St James’s Hospital and TILDA investigator, added:

“Many older people want to know what they can do to protect their memory and brain health as they age. The positive news is that many of the risk factors we’ve identified including hearing loss, high blood pressure, or physical inactivity are treatable. Over 70% of older adults in Ireland live with four or more modifiable dementia risk factors, many of which remain untreated. By systematically identifying and addressing these risks we could potentially prevent more than 100,000 cases of dementia.”

Professor Sean Kennelly, Director of the Tallaght Institute for Memory and Cognition and Clinical Associate Professor in Medical Gerontology at Trinity College Dublin, emphasised the public health implications:

“This important study quantifies the opportunity lost for thousands of people in Ireland in the last decade to optimise their brain health and minimise their risk for developing dementia in later life. Ireland can lead in dementia prevention by integrating risk factor management into our national health policy."

Regius Professor Rose Anne Kenny, Principal Investigator of TILDA noted:

“The message is clear: dementia is not an inevitable part of ageing. By addressing treatable risk factors, we can significantly reduce its incidence and help people live healthier, more cognitively active lives. The TILDA dataset, now a mature national resource, offers unparalleled insight into the health and ageing of Ireland’s older population. Its depth and longevity make it an invaluable tool for guiding policy, improving clinical care, and realising the goal of healthier ageing for all.”

Policy Implications

 These findings from TILDA underscore an urgent need for national brain health strategies and the integration of dementia risk management into Ireland’s healthcare system. Preventing or delaying dementia through modifiable risk factors could dramatically reduce healthcare costs and improve quality of life for older adults.

Read: You can view the full paper: “How prevalent are modifiable dementia risk factors in Ireland? A 12-year observational study in community-dwelling older adults”, at the following link:  https://bmjopen.bmj.com/content/15/11/e106032

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