Our study was based on a government project called “Bring Tangible Benefits to the People” of Xiamen City, Fujian Province, China. The project focused on residents aged ≥ 65 years and aimed to explore the current status, including the prevalence, risk factors, and management of dementia and MCI in Xiamen City. Our results showed that the overall prevalence of dementia in Xiamen was 5.4%. A previous large-sample report for Chinese individuals aged ≥ 65 years involving 32552 respondents in 2019 and 10276 in 2014 indicated a 5.60% and 5.14% prevalence of dementia, respectively (15, 16). Another study encompassing 46011 Chinese respondents aged ≥ 60 years in 2020 reported a 6.0% prevalence of dementia (7). Thus, the prevalence of dementia in our survey was consistent with previous findings in Chinese individuals. However, compared with the prevalence of dementia in other countries, our findings showed a significantly lower prevalence than in Japan (11.3%) (17), Latin America and the Caribbean (10.66%) (18), South Korea (9.20%) (19), the United States (8.5%) (20), and India (7.4%) (21). Conversely, it was higher than Benin (3.2%) (22) and Portugal (3.65%) (23). The prevalence of dementia varies greatly among countries. Several factors were considered to contribute to these variations, such as genetic factors, sample size, diverse diagnostic criteria, and environmental risks. Moreover, we identified 1553 individuals with MCI, yielding a prevalence of 7.7%. The prevalence of MCI ranged from 5.0–36.7%% in different regions in individuals aged ≥ 60 years (14). Two reports on the Chinese population aged ≥ 60 years indicated that the MCI prevalence was 14.7% in 2018 and 15.5% in 2020, respectively (7, 10). Another report showed that the prevalence of MCI was 19.5% (23.4% in rural and 16.8% in urban areas) among Chinese individuals aged ≥ 65 years (24).
Our results showed that two unmodifiable risk factors, increasing age and female sex, were associated with dementia and MCI, similar to another study (25). Some alterations in the brain caused by the aging process, including hippocampus atrophy, amyloid-β over-production and accumulation, and neuroinflammatory disturbances, could accelerate cognitive decline (26). Additionally, two modifiable risk factors, hypertension and DM, were related to dementia and MCI. Previous reports have also indicated a remarkable increase in the MCI risk among people with hypertension and DM (27). Another meta-analysis suggested that DM resulted in gray matter atrophy and accelerated brain aging (28). Moreover, hypertension and DM are associated with amyloid-β burden and contribute to the pathophysiology of MCI (29). To date, there is no effective medical treatment for MCI. Therefore, interventions with modifiable risk factors are particularly important for preventing cognitive deterioration. Healthy lifestyles and regular use of drugs to avoid hypertension and DM were considered to lower the risk of developing cognitive decline (30, 31). While we maintained scientific rigor throughout this study, we would like to acknowledge a few limitations. First, despite enrolling over 20000 people from 10 communities in Xiamen City, we had to invite more participants from other cities. Second, we did not classify dementia according to its etiology, such as vascular dementia or Alzheimer’s disease. Finally, compared with previous large-scale studies on China, we chose fewer possible modifiable risk factors.
After screening, we identified a total of 2635 participants with dementia or MCI and advised them to visit the general hospital for further diagnosis and treatment. However, we found that only 5.5% (144/2635) of the older adults found with dementia or MCI chose to be referred to the hospital for further diagnosis and treatment during follow-up visits. We consider the low referral rate of positive participants can be attributed to several reasons. Due to the COVID-19 pandemic, patients and their family members were afraid of being infected with the virus when they came to the hospital. Others simply consider amnesia or cognitive dysfunction to be a normal aging process; hence, they were reluctant to seek medical attention. Additionally, education and knowledge about dementia and MCI have not been popularized, making it challenging for family members to recognize the detriment and prognosis of cognitive impairment. Recommendations have been made to improve the referral rate of patients with cognitive impairment from the community. Firstly, specialists in cognitive disorders from general hospitals should conduct more lectures and presentations on dementia or MCI to train doctors in the community. Moreover, government departments should provide more science education initiatives and free clinics for older adults in communities to raise public awareness of cognitive disorders.