Background

Alzheimer's disease (AD) is the most common type of dementia in the elderly (60%-80% of dementia cases). It has insidious onset and progressive development, seriously eroded the patients' memory encoding, cognitive judgment and behavior regulation ability (mainly damaged the hippocampus, cerebral cortex and other brain areas). And the course of the disease usually lasts for 5 to 10 years.

Figure1 shows the degree of brain damage in AD patients: early AD (upper left), mild to moderate AD (upper right), severe AD (lower).(Tencent, 2023)

Ultimately, it leads to the patient completely losing their basic ability to live independently, imposing a heavy burden on individuals, families and society. From the perspective of symptom development, the deterioration of AD patients shows a distinct phased pattern. In the early stage, it is centered around "remembering the new and forgetting the old", with a significant decline in recent memory but still able to recall past events clearly. The symptoms are concealed and easily overlooked. Mid-term memory impairment has worsened, and even past events have begun to be forgotten. Cognitive impairment has extended to the fields of language, spatial orientation, and judgment, accompanied by behavioral abnormalities, seriously affecting daily life. In the advanced stage, brain function severely declines, making it impossible to communicate, eat independently, and experience incontinence. After long-term bed rest, complications such as lung infection and malnutrition are prone to occur, significantly increasing the difficulty of care.

Globally, Alzheimer's disease (AD) is one of the main causes of disability and dependence among people aged 65 and above. According to data from the World Health Organization (WHO) in 2021, there are 57 million Dementia patients worldwide, with over 60% living in low - and middle-income countries (LMICs), and nearly 10 million new cases of dementia occur each year (World Health Organization, 2025). AD is the most common type of dementia, accounting for 60% to 70% of all dementia cases (World Health Organization, 2025). The global number of dementia patients is projected to increase from 55 million in 2020 to 78 million in 2030 and reach 139 million by 2050, with a new case emerging every 3.2 seconds (Alzheimer's Disease International, 2020). It is worth noting that the proportion of patients from low - and middle-income countries (LMICs) has reached 60% and is projected to rise to 71% by 2050 (Alzheimer's Disease International, 2020). The growth rate of patients in these regions is significantly higher than that in high-income countries. It is expected that the number of patients will almost double every 20 years in the coming decades (Alzheimer's Disease International, 2020).

What is even more alarming is that AD is breaking the traditional perception of a "disease of the elderly" and showing a significant trend of affecting younger people. According to the "Insight Report on the Needs of Alzheimer's Disease Patients" in China, the proportion of AD patients under the age of 60 has reached 21.3%, far exceeding the international average of 5% to 10%. Among them, 14.7% of the patients were aged 50 to 59, 4.1% were aged 40 to 49, and even 2.5% of the patients were under 40 when they fell ill. This trend not only threatens the health of the patients, but also has an impact on their career development and family stability.

Young-onset dementia (under 65 years old) is receiving increasing attention. Global data based on meta-analysis shows that the age-standardized prevalence rate among people aged 30-64 is 119.0 per 100,000, corresponding to approximately 3.9 million early-onset dementia patients worldwide (Hendriks et al., 2023). The global age-standardized incidence rate has increased from 0.17 per 100,000 people for those aged 30-34 to 5.14 per 100,000 people for those aged 60-64. The overall incidence rate for those aged 30-64 is 11 per 100,000 people, equivalent to approximately 370,000 new cases of early-onset dementia worldwide each year (Hendriks et al., 2023). In the United States, research estimates that approximately 110,000 out of 100,000 people aged 30 to 64 suffer from early-onset dementia, totaling about 200,000 Americans with Alzheimer's Disease Facts and Figures (Alzheimer's Association, 2025).

Through our research, we have found that at the treatment level, there is currently no cure for AD. The commonly used clinical drugs can only "relieve symptoms and delay progression", and the economic burden is heavy. Cholinesterase inhibitors (such as donepezil and carbapatine) cost approximately 300 to 800 yuan per month, while N-methyl-D-aspartate (NMDA) receptor antagonists (such as Memantine) cost about 500 to 1,200 yuan per month. If a patient enters the middle or advanced stage and requires combined medication, the monthly drug cost will increase to 800 to 2,000 yuan and will need to be continuously paid for a long time. What's more, patients need dedicated care in the later stage (such as hiring caregivers or moving into nursing homes), and the monthly care costs are mostly between 5,000 and 15,000 yuan, which is a "heavy burden" for ordinary families.

The global medical economy is burdened heavily. In 2019, the global economic cost of dementia was estimated at 1.3 trillion US dollars, of which approximately 50% was attributed to informal care (unpaid care provided by family members and friends), social care costs accounted for about 40%, and direct medical costs accounted for approximately 20% (Wimo et al., 2023). In the United States, the total cost of medical care and long-term care for dementia patients is expected to reach 384 billion US dollars in 2025 and approach 1 trillion US dollars by 2050 (Alzheimer's Association, 2025).

Meanwhile, the problem of poor medication compliance among patients further weakens the treatment effect: at the cognitive level, patients often forget that they "need to take medicine" or mistakenly believe that they "have already taken it". Psychologically, early-stage patients deny their illness and consider taking medicine a waste of money, while those in the middle and late stages refuse to swallow or even vomit due to taste or cognitive impairments. Some patients also resist treatment due to concerns about the side effects of the drugs, which makes it more difficult to control the condition.

Figure2: 2021 Age Grouping of AD and other dementias in China (left) (Wang et al., 2024)

The number and age of people aged 65 or above with Alzheimer's dementia in the United States in 2025 (right) (Alzheimer's Association, 2025)

Figure3: Comparison of Socio-economic Burdens between Alzheimer's Disease and Malignant Tumors (Jia et al., 2018)

In addition, the supply of long-term care resources is seriously insufficient, and there is a shortage and uneven distribution of professional caregivers, further intensifying the pressure on family care. Through interviews with some professionals, we have learned that the medical system has limited support for chronic disease management and weak grassroots diagnosis and treatment capabilities, which leads to frequent emergency visits and hospitalizations for patients, pushing up overall medical expenditures.

Delayed diagnosis is a universal pain point worldwide. Most patients are diagnosed at the middle or advanced stage, missing the best intervention window period. Research shows that in high-income countries, only 20% to 50% of dementia cases are identified and recorded in primary care. This "treatment gap" is even more severe in LMICs. An Indian study revealed that 90% of patients were undiagnosed (Alzheimer's Disease International, 2020). If these statistics are generalized globally, approximately three quarters of dementia patients have not yet received a diagnosis and thus do not have access to the treatment, care, and organized support that a formal diagnosis can offer (Alzheimer's Disease International, 2020). To this end, the WHO has put forward the core goal of increasing the diagnosis rate and improving the quality of life of Dementia patients and their caregivers in the Global Dementia Action Plan 2017-2025 (World Health Organization, 2025).

Figure4: The duration from the onset of symptoms to the visit of patients with Alzheimer's disease (People's Daily Online, 2023)

In recent years, research on the "gut-brain axis" has provided a brand-new direction for AD intervention. As a complex bidirectional interaction system between the central nervous system and the gut microbiota, the gut microbiota can synthesize and release neuroactive substances such as short-chain fatty acids (SCFAs) and bioactive amines, which reach the brain through multiple pathways to affect neuronal activity.

Through literature research, we found that AD patients generally have intestinal flora disorders, especially a deficiency of butyric acid (the main metabolic product of the intestinal flora) among short-chain fatty acids, and there is a certain association with the deterioration of neurodegenerative conditions.

Based on our team's research, it was found that there are obvious shortcomings in the current society's understanding and response to AD: on the one hand, due to the omissions in previous studies, there is still a huge research space for AD in drug development and disease mechanism analysis; On the other hand, the public does not attach sufficient importance to the prevention of AD. Due to the misconception that "the disease progresses slowly and is irreversible", most people neglect early intervention, resulting in a large number of patients missing the best opportunity for prevention and control. Therefore, it is of vital importance to develop a drug or therapy with early preventive effects.

Figure5: A survey shows that patients with Alzheimer's disease face many difficulties, and innovative drugs and therapies are in urgent need of research and development (People's Daily Online, 2023) Figure6: A wordcloud shows the public's common impression of AD

Therefore, this project focuses on the dual needs of "prevention and treatment" of AD. Using synthetic biology technology and probiotics as the chassis, we have introduced butyrate synthesis genes and other accessory components to construct the engineered yeast for the development of preventive healthcare products. The aim is to regulate intestinal function and supplement butyric acid Provide a brand-new, safe, economical and sustainable solution for the prevention and control of AD.

Reference

Details

Alzheimer's Association. (2025). 2025 Alzheimer's disease facts and figures. Alzheimer's & Dementia, 21(4), Article e70235.

Alzheimer's Disease International. (2020). Dementia statistics.

Hendriks, S., Peetoom, K., Bakker, C., et al. (2023). Global incidence of young-onset dementia: A systematic review and meta-analysis. Alzheimer's & Dementia, 19(7), 2865–2873.

Jia, J., Wei, C., Chen, S., et al. (2018). The cost of Alzheimer's disease in China and re-estimation of costs worldwide. Alzheimer's & Dementia, 14(4), 483–491.

People's Daily Online. (2023, September 21). 阿尔茨海默病患者需求洞察报告 [Alzheimer's disease patients' demand insight report]. Zhihu.

Tencent. (2023, July 15). 阿尔茨海默病对大脑的影响（下）——大脑的改变 [The impact of Alzheimer's disease on the brain (Part 2)—Changes in the brain]. Tencent News.

Wang, G., Qi, J., et al. (2024). Chinese report on Alzheimer's disease 2024. Theory and Practice of Diagnostics, 23(3), 219–256.

Wimo, A., Seeher, K., Cataldi, R., et al. (2023). The worldwide costs of dementia in 2019. Alzheimer's & Dementia, 19(7), 3192–3200.

World Health Organization. (2025). Dementia fact sheet.