How does dementia affect Asians and Caucasians differently
Most of us believe that Alzheimer’s and dementia are no respecters of persons, meaning that the conditions don’t skip over or target certain types of individuals. Apart from long-proven contributors such as stroke, diabetes, and high blood pressure, researchers have recently identified one more risk factor: race.
Here's what multiple studies[1] have concluded about race (for those aged 65 to 90) and dementia risk in the US:
- African Americans: 38% occurrence (highest risk)
- American Indian/Alaska Natives: 35%
- Latinos: 32%
- Whites: 30%
- Asian Americans: 28%
- Pacific Islanders: 25%
Local[2] studies have also shown that the prevalence of dementia in Singapore is much lower than seen in the West. In Singapore, just 1 in 10[3] individuals (10%) above the age of 60 suffer from dementia. Similarly, in Hong Kong, the prevalence rate of dementia is only 5-8% for persons aged above 65, and 20 to 30% for those aged 80 and above[4].
However, this does not necessarily mean dementia is far more widespread in Europe and America – dementia is a complex condition that might not be recognised in certain countries; its statistics depend on the willingness of people to present themselves to be diagnosed.
In fact, newer research suggests that Asians are genetically far more at risk of developing dementia. Let’s find out why.
What is the difference between Alzheimer’s Disease and Dementia?
Although the terms are often used interchangeably, they refer to different things.
Dementia is a syndrome of acquired cognitive impairment which is severe enough to interfere with one's work and social lives.
The most common disease mechanisms causing dementia include
- Alzheimer Disease which is theorised to be caused by accumulation of abnormal toxic amyloid proteins and
- Vascular dementia, due to damage to blood vessels in the brain.
The 2 can also co-exist in the same person who is then thought to have "mixed dementia"
Condition | Risk factors | What it is | How it affects us |
---|---|---|---|
Vascular dementia (VAD) | High blood pressure, obesity, smoking, diabetes, and more. | A common subtype of dementia that leads to a reduced supply of blood, oxygen, and nutrients to the brain, as a result of damaged blood vessels. | VD can lead to progressive memory loss, intellectual decline, and personality changes. It affects one’s ability to think, learn and make decisions. |
Alzheimer’s Disease (AD) | A combination of genetic and lifestyle factors. | The nerve cells of the brain are destroyed, causing the shrinking of the brain. | Alzheimer's disease is another common type of progressive dementia. |
How common is Alzheimer’s and vascular dementia in Asians?
Nearly half (45.5%) of dementia cases in Singapore are vascular dementia cases. This corresponds to roughly 41,000 VAD cases in 2018. The number of vascular dementia cases is set to increase to approximately 76,000 by 2030.
Other less common types of dementia include:
- Lewy body dementia
- Frontotemporal dementia
Dementia: Ethnic comparison of Asia with the United States
In a recent article by The Straits Times[5], research by Dementia Research Centre Singapore (DRCS) sheds light on “Asian dementia”. Here are the findings:
- Asians are three times more likely than Caucasians to suffer from cerebral small vessel disease, a narrowing of small blood vessels in the brain that appear as white matter lesions
- These white matter lesions increase an individual’s risk of rapid cognitive decline and dementia
- Small vessel disease results in more brain shrinkage in the absence of the APOE4 gene, a risk factor gene that’s much lower in Asian patients
- One in three Asian patients has the tau protein in the brain, which is known to be a risk factor for dementia
Next, it was initially thought that in the Asia-Pacific region, most people with dementia live in developed or higher income countries[6].
Country | Publication Year | Sample Size | Age range year | Prevalence % |
---|---|---|---|---|
India[8] | 2010 | 2,466 | > 55 | 3.77 |
China[9] | 2010 | > 55 | 2.99 | |
Japan[10] | 2009 | > 65 | 11.0 | |
Korea[11] | 2008 | 1,118 | > 65 | 6.3 |
Thailand[12] | 2008 | 2,311 | > 45 | 2.35 |
Sri Lanka [13] | 2003 | 703 | > 65 | 3.98 |
Australia [14] | 2001 | 146 | 3.6 | |
Taiwan [15] | 1998 | 2,915 | > 65 | 3.7 |
However, when making comparisons with developing countries, we need to account for factors such as education, responses to diagnostic tests and even cultural influences. For example, dementia symptoms may be normalised due to the traditional Chinese belief that old people return to a childish state.
Further, functional disability associated with cognitive decline may be underreported due to;
- Lack of elder participation in functional activities
- More prominent physical morbidities that mask cognitive decline
All these possibly account for lower prevalence of dementia in developing countries.
Country | Publication Year | Sample Size | Age range year | Incidence reported | Incidence, % (annualized) |
---|---|---|---|---|---|
Japan[16] | 2009 | 828 | > 65 | 3.23/100 person-years | 3.23 |
China[17] | 2008 | 1,553 | > 60 | 0.9% at 2 years | 0.45 |
Australia[18] | 2003 | 377 | > 75 | 16.7% at 6 years | 2.78 |
India[19] | 2001 | 2,698 | > 55 | 0.17/100 person-years | 0.17 |
>65 | 0.32/100 person-years | 0.32 | |||
Taiwan[20] | 1998 | 2,507 | > 65 | 1.28/ year | 1.28 |
Lastly, in general, studies[7] suggest that Asian populations appear to have a larger proportion of vascular dementia (VAD) cases, while Caucasians suffer more from Alzheimer’s Disease (AD).
Japan[8] was initially thought to have a substantially lower prevalence of AD and a higher prevalence of VAD. However, more recent[9] studies have shown decreases in VAD and increases in AD amongst the Japanese. This could reflect the following:
- Improved control over cardiovascular risk factors that lead to VAD
- An increase in AD due to Western risk factors such as a fat-rich diet and cholesterol
This suggests that on top of genetic risks, our diet and lifestyle also plays an important role in relation to developing and managing dementia.
What other factors increase one’s risk of dementia?
While Alzheimer’s is linked to genetic factors, researchers have found links between dementia and the following factors*:
Factor | Affected demographic(s) | How it affects Singaporeans |
---|---|---|
High Blood Pressure | Studies have concluded that African Americans are most likely to have high blood pressure, thus placing them at greater risk of dementia. | In Singapore, 1 in 4 people aged 30-69 has high blood pressure. Every day, 17 people die from heart disease and stroke. |
Type 2 Diabetes | Both African Americans and Hispanics have a higher prevalence of diabetes compared to Whites. Interestingly, African Americans and Native Americans with type 2 diabetes have a 40-60% higher risk of developing dementia than Asian Americans with type 2 diabetes. | Over 400,000 Singaporeans live with Type 2 Diabetes, and this number is set to surpass one million by 2050. The lifetime risk of developing diabetes is one in three[10] among Singaporeans. |
Stroke | African Americans are 2.7 times more likely than other races to get a stroke, which in turn results in an increased risk of vascular dementia. | The number of stroke episodes in Singapore increased from 5,890 episodes (2010) to 8,849 episodes in 2019. |
Lower education and income levels | A study found that among 5,055 Shanghai Chinese residents aged 65 and above, the prevalence rate of dementia was 4.6%, with only 65% of these individuals having a clinical diagnosis of AD. Nearly half (47%) of those diagnosed had no formal education, while 29% had no more than 7 years of it. | Three risk factors for dementia include: > Living in rural areas > A lower education level > Having a lower income level The lack of education is a significant and independent risk factor for the prevalence of dementia. |
Whatever your race, culture, or country of origin, it is crucial to have a keen knowledge of how Alzheimer’s and dementia might affect you and your loved ones. If you suspect that someone you love might be dealing with the condition, contact us today for the help you need.
References
- https://www.verywellhealth.com/ethnic-disparities-how-your-race-impacts-your-risk-of-dementia-3986388
- Sahadevan, S., Saw, S. M., Gao, W., Tan, L. C. S., Chin, J. J., Hong, C. ye, & Venketasubramanian, N. (2008). Ethnic Differences in Singapore’s Dementia Prevalence: The Stroke, Parkinson’s Disease, Epilepsy, and Dementia in Singapore Study. Journal of the American Geriatrics Society, 56(11), 2061–2068. https://doi.org/10.1111/j.1532-5415.2008.01992.x
- https://www.healthhub.sg/programmes/160/AAP/dementia
- Legislative Council of the Hong Kong Special Administrative Region - Care services for elderly persons with dementia. (n.d.). Www.legco.gov.hk. https://www.legco.gov.hk/research-publications/english/essentials-1617ise10-care-services-for-elderly-persons-with-dementia.htm#:~:text=According%20to%20the%20Hospital%20Authority
- https://www.straitstimes.com/singapore/health/ntu-launches-centre-to-study-how-dementia-develops-in-asians
- Venketasubramanian, N., Sahadevan, S., Kua, E. H., Chen, C. P., & Ng, T. P. (2010). Interethnic differences in dementia epidemiology: global and Asia-Pacific perspectives. Dementia and geriatric cognitive disorders, 30(6), 492–498. https://doi.org/10.1159/000321675
- Jorm A. F. (1991). Cross-national comparisons of the occurrence of Alzheimer's and vascular dementias. European archives of psychiatry and clinical neuroscience, 240(4-5), 218–222. https://doi.org/10.1007/BF02189530
- Shadlen, M.-F., Larson, E. B., & Yukawa, M. (2000). The epidemiology of Alzheimer’s disease and vascular dementia in Japanese and African-American populations: the search for etiological clues. Neurobiology of Aging, 21(2), 171–181. https://doi.org/10.1016/s0197-4580(00)00115-9
- Yamada, M., Sasaki, H., Mimori, Y., Kasagi, F., Sudoh, S., Ikeda, J., Hosoda, Y., Nakamura, S., & Kodama, K. (1999). Prevalence and Risks of Dementia in the Japanese Population: RERF’s Adult Health Study Hiroshima Subjects. Journal of the American Geriatrics Society, 47(2), 189–195. https://doi.org/10.1111/j.1532-5415.1999.tb04577.x