DESK REVIEWS | 06.02.05. What is the average age of onset?

DESK REVIEW | 06.02.05. What is the average age of onset?

No information was found on this.

So far, two local studies have examined the age of onset of dementia in Hong Kong. According to a retrospective case notes review of 454 consecutive people with dementia and mild cognitive impairment at Princess Margaret Hospital in Hong Kong from 1999 to 2004, the average age of dementia onset was 76.7 ± 8.7. The median duration from the symptom onset to medical consultation was 2 years (range from 4 months to 10 years) with a mean of 14.8 months (Sheng, Law, & Yeung, 2009). Another earlier study found that the age of onset of Alzheimer’s disease was related to the frequency of Apolipoprotein E epsilon 4 allele (ApoE) among 65 people with dementia. The mean age of onset identified was 73.7 (Mak et al., 1996).


Mak, Y., Chiu, H., Woo, J., Kay, R., Chan, Y., Hui, E., et al. (1996). Apolipoprotein E genotype and Alzheimer’s disease in Hong Kong elderly Chinese. Neurology, 46(1), 146-149.

Sheng, B., Law, C. B., & Yeung, K. M. (2009). Characteristics and diagnostic profile of patients seeking dementia care in a memory clinic in Hong Kong. International psychogeriatrics, 21(2), 392-400.

The age of onset of dementia has been studied in dementia cohorts and evaluated in hospital-based studies. In India, the proportion of patients with early-onset dementia is higher (49.9%) in comparison to developed countries (7-30%) (Das, Ghosal and Pal, 2012; Alladi et al., 2011). A study examining subtypes of dementia from a memory clinic in South India reported the mean age of onset of dementia as 66.3 years (Alladi et al., 2011). This is likely to be reflective of the demographic and epidemiologic profile of India. For example, lower levels of education and socioeconomic status, contribute to a higher number of individuals with vascular dementia (who are typically younger than persons with AD patient) (Alladi et al, 2011). Furthermore, lower referral rates of older elderly to hospitals as a result of lack of awareness and ‘sociocultural’ protection of elderly with memory loss in developing countries may also be contributing towards the lower age of onset reported by clinic studies (Alladi et al., 2011).


Alladi, S., Mekala, S., Chadalawada, S. K., Jala, S., Mridula, R., & Kaul, S. (2011). Subtypes of \Dementia: A Study from a Memory Clinic in India. Dementia and Geriatric Cognitive Disorders, 32(1), 32–38.

Das, S., Ghosal, M., & Pal, S. (2012). Dementia: Indian scenario. Neurology India, 60(6), 618.

We could not identify data on the average age of dementia onset in Indonesia.

No data was found due to a paucity of data.

It is difficult to indicate when dementia begins because the onset is gradual. However, Young Onset Dementia (YOD) typically occurs before the age of 65 (Alzheimer’s Disease International (ADI) and World Health Organization (WHO), 2012). There is no information on the average age onset in Kenya.


Alzheimer’s Disease International (ADI) and World Health Organization (WHO). (2012). Dementia: A public health priority. United Kingdom.

In the absence of any prevalence studies, the calculation of the average age of dementia onset is not possible.

Cullum et al., (2018) reported on 1106 referrals to a specialist memory service and calculated a mean age of onset of 74.6 years. They also showed that the onset of dementia in Māori and Pacific people referred to a specialist memory clinic was 8.5 years and 5 years earlier respectively, when compared to those of European/Pakeha ethnicity (table 41).

Table 41

Ethnicity Age (yrs) (95% CI)
NZ European 79.1 (77.9 – 80.4)
Pacific People 73.9 (72.5 – 75.2)
Maori 70.6 (68.4 – 72.9)



Cullum S., Mullin K., Zeng I., Yates S., Payman V., Fisher M., et al. (2018). Do community-dwelling Maori and Pacific peoples present with dementia at a younger age and at a later stage compared with NZ Europeans? Int J Geriatr Psychiatry. 33(8):1098-104.

Specific age of onset data is not found for South Africa; however, globally, age is identified as an important risk factor with the risk of developing dementia reported by the 10/66 Group as increasing for those 60 years and over in 21 Global Burden of Disease regions (De Jager et al., 2017; Prince et al., 2003).


De Jager, C.A., Msemburi, W., Pepper, K., & Combrinck, M. (2017). Dementia Prevalence in a Rural Region of South Africa: A Cross-Sectional Community Study. Journal of Alzheimer’s Disease, 60(3), 1087–1096.

Prince, M, Acosta, D., Chiu, H., Scazufca, M., & Varghese, M. (2003). Dementia diagnosis in developing countries: a cross-cultural validation study. The Lancet, 361, 909–917.