Risk Factors of Dementia

Dementia is a group of clinical syndromes caused by brain pathology. Its core features include the gradual decline of memory, language, comprehension, judgment, behaviour, and daily living abilities, accompanied by changes in personality and emotions. With population ageing, dementia has become an important global public health challenge. According to the latest research such as the Lancet Commission on Dementia Prevention, Intervention, and Care, about 40–45% of dementia cases are associated with modifiable risk factors.

I. Non-modifiable Risk Factors

1. Age
   Age is the most important and unchangeable risk factor. Studies show that the risk of dementia rises significantly after age 65, and about one-third of people over 90 are affected. With increasing life expectancy, population ageing continues to drive up the overall prevalence of dementia.
2. Genetics
   Genes play an important role in the causes of dementia. The most representative gene is APOE ε4, which significantly increases the risk of Alzheimer’s disease. Some familial gene mutations (such as PSEN1, PSEN2, APP) can directly cause early-onset Alzheimer’s disease, usually appearing at ages 40–50.
3. Down Syndrome
   Patients with Down syndrome have an extra chromosome 21, leading to excessive accumulation of β-amyloid protein. They often develop early-onset Alzheimer’s disease in middle age. This group has a much higher risk of dementia than the general population.
4. Sex and Ethnicity
   Women have a higher overall prevalence than men due to longer life expectancy. Certain ethnic groups, such as African and Latino populations, have relatively higher risk because of the higher prevalence of cardiovascular disease.

II. Modifiable Risk Factors

1. Cardiovascular and Metabolic Disorders

• • Hypertension: Long-term uncontrolled hypertension damages cerebral blood vessels, increasing the risk of vascular dementia.
  • Diabetes: Hyperglycaemia and insulin resistance accelerate brain degeneration and are closely linked to Alzheimer’s disease.
  • Hypercholesterolaemia and obesity: Atherosclerosis leads to insufficient cerebral blood flow, increasing neuronal damage.
  • Heart disease and stroke history: Directly cause interruption of cerebral blood flow, leading to cognitive decline.

2. Lifestyle

• • Smoking: Nicotine and carbon monoxide damage cerebral blood vessels, increasing the risk of vascular dementia.
  • Alcohol abuse: Long-term heavy drinking can cause alcohol-related brain disease and accelerate neurodegeneration.
  • Physical inactivity: Poor fitness and reduced cerebral blood flow increase the risk of degeneration.
  • Unhealthy diet: High-fat, high-sugar diets are associated with brain inflammation; conversely, the Mediterranean diet can reduce risk.

3. Education Level and Cognitive Reserve
Low education level and lack of cognitive stimulation reduce “cognitive reserve,” making the brain more vulnerable to pathology. Studies show that people with higher education or continuous cognitive activity have lower risk and slower disease progression.

4. Social Isolation and Mental Health
Social isolation, lack of interpersonal interaction, and depression are all associated with increased dementia risk. Social activities stimulate brain neural networks and slow degeneration. Depression may accelerate cognitive decline through neurochemical changes and brain inflammation.

5. Hearing Loss
The Lancet Commission report points out that hearing loss is one of the most important and modifiable risk factors. Hearing impairment reduces brain stimulation and increases social isolation, further accelerating cognitive decline. Using hearing aids or early intervention can significantly reduce risk.

6. Environmental Factors
Air pollution, heavy metal exposure, and living in resource-poor areas are all associated with increased dementia risk. Traumatic brain injury is also an important risk factor, especially repeated head injuries (such as in professional athletes).

III. Clinical and Public Health Implications

About 40–45% of cases are related to modifiable factors: controlling blood pressure, diabetes, quitting smoking, improving education and social activities can significantly reduce risk.

Early diagnosis and intervention: help slow disease progression and reduce family burden.

Multidisciplinary collaboration: psychiatry, neurology, nutrition, and community resources jointly intervene to provide comprehensive support.

Community education: enhance public understanding of dementia, reduce stigma, and promote inclusion.

IV. Conclusion

The risk factors of dementia include both non-modifiable and modifiable categories. Although age and genes cannot be controlled, cardiovascular disease, lifestyle, education level, social environment, hearing loss, and environmental factors are all modifiable.

In an ageing society, the challenge of dementia is becoming increasingly severe. Only through professional diagnosis, multidisciplinary collaboration, and community education can we truly improve the quality of life of patients and families, and promote social understanding and acceptance of dementia.