Nearly half of dementia cases can be prevented or delayed, study finds

Nearly half of dementia cases can be prevented or delayed, study finds

Addressing 14 modifiable risk factors throughout a person's life could potentially prevent or delay 45 percent of dementia cases worldwide, according to a report from the Lancet Commission on dementia prevention, intervention, and care. The findings, published July 31, 2024, suggest that these reductions are possible regardless of whether a person carries the APOE gene, also known as the Alzheimer's gene.

The report, led by University College London Professor Gill Livingston and authored by 27 experts, was presented at the Alzheimer’s Association International Conference in Philadelphia. The researchers warn that dementia is a growing global challenge; the number of people living with the condition is forecast to nearly triple from 57 million in 2019 to 153 million by 2050. This surge presents a threat to social care systems, with global health and social costs exceeding $1 trillion annually.

Expanding the Risk Profile

The 2024 report expands upon previous findings from 2017 and 2020. While 12 risk factors were previously identified, the new data adds two more: untreated vision loss in later life and high levels of low-density lipoprotein (LDL), or bad cholesterol, in midlife starting around age 40. According to Professor Livingston, these two new factors are associated with 9 percent of dementia cases, with LDL cholesterol accounting for 7 percent and vision loss for 2 percent.

The full list of 14 modifiable risk factors includes:

• Hearing impairment
• High LDL cholesterol
• Lower levels of education in early life
• Social isolation in later life
• High blood pressure
• Smoking
• Obesity
• Depression
• Physical inactivity
• Diabetes
• Excessive alcohol consumption
• Traumatic brain injury
• Air pollution
• Untreated vision loss

The commission identifies hearing impairment and high LDL cholesterol as the factors associated with the greatest proportion of people developing dementia, at 7 percent each. Lower education and social isolation follow at 5 percent each.

Life-Course Prevention and Quality of Life

The researchers emphasize that prevention should begin in childhood and continue through late life. Professor Livingston stated that while longer exposure to risk has a greater effect, it’s never too early or too late to take action.

Beyond preventing the onset of the disease, the report indicates that reducing these risks can increase the number of healthy years of life. For those who still develop dementia, these interventions may reduce the duration of ill health, which improves quality of life and provides cost-saving benefits for societies. For instance, Professor Livingston suggests that simple changes, such as incorporating walks or seated exercises for those who are sedentary, can help.

The commission provided 13 recommendations for governments and individuals. These include making hearing aids accessible to reduce cognitive decline and maintain social ties, ensuring children receive quality education, and implementing screening for vision impairment. There is also a call for detecting and treating high cholesterol from age 40.

Societal and Economic Implications

While some risks like exercise and alcohol consumption are manageable by individuals, other factors require systemic change. Fiona Carragher of the Alzheimer’s Society noted that air pollution, education inequalities, and social isolation are beyond individual control and necessitate joint action between industry and government.

The economic impact of these interventions is substantial. A separate study published in the Lancet Healthy Longevity journal used England as a model to show that population-level interventions could yield £4 billion in savings by reducing dementia rates. Dr. Naaheed Mukadam, a co-author of the report, suggested that prioritizing primary prevention, such as reducing sugar and salt intake and restricting smoking, could profoundly affect dementia prevalence and inequalities.

The report also highlights disparities in risk. While dementia prevalence is declining in some high-income countries—potentially due to better healthcare and increased physical and cognitive resilience—it continues to rise in low- and middle-income countries. The authors argue that those in socio-economically disadvantaged groups and low-income nations may actually see even greater risk reductions if these 14 factors are addressed.

Future Directions and Limitations

Despite the findings, Dr. Susan Kohlhaas of Alzheimer’s Research UK cautioned that genetics and age remain the primary risk factors for dementia. The commission also noted that its 45 percent reduction estimate assumes risk factors are causal and can be entirely eliminated, though some associations may only be partly causal. For example, they noted that while midlife depression may be a cause, late-life depression might be a result of dementia.

The commission is now calling for more research into additional risk factors and the scaling of evidence-based programs. They also highlighted the potential of blood biomarkers to make diagnosis less intrusive and more affordable. Regarding treatment, the authors noted the emergence of anti-amyloid β antibodies but cautioned that these are new and require more long-term data and transparency concerning side effects.

For those already living with dementia, the report advocates for nonpharmacological approaches, such as activities tailored to a person's interests, to improve quality of life and reduce symptoms. They also recommend multi-component coping interventions for family caregivers to address risks of anxiety and depression.