Alzheimer’s disease (AD) is a progressive and irreversible neurodegenerative brain disease that impairs thinking, memory and independence, and represents the most common cause of dementia.1,2
Dementia is an umbrella term for several diseases that are principal contributors to mental disability and the need for care in old age.1 Worldwide, up to 80% of the 50 million patients with dementia are thought to have AD.1,3
AD and other forms of dementia are a World Health Organization priority and are listed among the top 10 causes of death worldwide, ranking 2nd in high-income countries worldwide.4 In Europe, the number of affected people will increase considerably from about 10 million today to about 14 million people in 2030 and will almost double by 2050.5,6
It is important to note that AD is not a normal part of ageing, and older age alone is not sufficient to cause the disease.1 AD operates out of sight, slowly developing over many years to cause damage to the brain.7 Short-term memory loss, forgetting recent events and conversations, or struggling to follow a series of instructions are typically the first signs of the disease. Other early symptoms include confusion, difficulty finding words, or changes in mood and personality.1
In the last ten years the terminology "MCI (mild cognitive impairment) due to AD" has been introduced in the characterization of subjects presenting some mild cognitive symptoms, which do not affect the individual's ability to carry out everyday activities. However, in addition to the clinical and cognitive assessment that may detect MCI, documentation of amyloid beta accumulation in the brain is required to confirm a suspected diagnosis of MCI due to AD.2
Today, we understand Alzheimer’s disease to be a continuum as it can be present for decades before it is even suspected.7 The neuropathological changes in the brain leading to synaptic dysfunction can begin up to 20 years before the first symptoms appear.1,7 Even then, it often goes undetected for far too long. People with AD and their loved ones either overlook early signs of the disease, or see them as ‘senior moments’ - just part of getting older.9
Risk Factors for Alzheimer's Disease10-13
Non-Modifiable Risk Factors
- Ageing: AD risk doubles every 5 years after age 65
- Positive family history
- Female gender
- Genetic predisposition & susceptibility (trisomy 21, rare mutations in dominantly inherited AD genes, and allele ε4 of ApoE gene in sporadic AD)
- Environmental factors
Modifiable Risk Factors
- Lifestyle, such as low physical activity, smoking, unhealthy diet, harmful alcohol use, social isolation, or cognitive inactivity
- Health conditions, such as hypertension, type 2 diabetes, heart disease, depression, dyslipidemia, hyperhomocysteinemia, hearing loss, or obesity
- Others, such as lower levels of education, certain medication, traumatic brain injury, or sleep disturbance
Age, genetics, family history, and environmental factors are the so called non-modifiable risk factors of AD. While age is the most dominant risk factor for cognitive decline, AD dementia is not a natural or inevitable consequence of ageing.12 Studies have shown that a variety of modifiable risk factors, such as lifestyle-related risk factors, certain medical conditions, social isolation, and cognitive inactivity do correlate with the development of cognitive impairment.12
The existence of potentially modifiable risk factors means that prevention of dementia is possible through a public health approach, including the implementation of key interventions that delay or slow cognitive decline.13
WHAT'S NEXT
The Stages of Alzheimer's Disease
Today, we understand Alzheimer’s disease to be a continuum. By the time patients show symptoms, the underlying processes of the disease have been at work for up to 20 years.
References
1. 2021 Alzheimer's disease facts and figures. Alzheimers Dement. 2021;17(3):327-406.
2. Masters CL, Bateman R, Blennow K, et al. Alzheimer’s disease. Nat Rev Dis Primers. 2015;1:15056.
3.World Health Organization (WHO). Dementia. www.who.int/health-topics/dementia. Accessed April 16, 2021.
4.World Health Organization (WHO). The top 10 causes of death. December 2020. www.who.int/news-room/fact-sheets/detail/the-top-10-causes-of-death. Accessed April 16, 2021.
5.Alzheimer’s Disease International. World Alzheimer Report 2015. The global impact of dementia: An analysis of prevalence, incidence, cost and trends. https://www.alzint.org/u/WorldAlzheimerReport2015.pdf. Accessed April 16, 2021.
6.Alzheimer Europe. Cost of illness and burden of dementia in Europe - Prognosis to 2030. www.alzheimer-europe.org/Research/European-Collaboration-on-Dementia/Cost-of-dementia/Prognosis-to-2030. Accessed April 16, 2021.
7.Jack CR Jr, Bennett DA, Blennow K, et al. NIA-AA Research Framework: Toward a biological definition of Alzheimer's disease. Alzheimers Dement. 2018;14(4):535-562.
8.Vos SJ, Verhey F, Frölich L, et al. Prevalence and prognosis of Alzheimer's disease at the mild cognitive impairment stage. Brain. 2015;138(Pt 5):1327-1338.
9.Wilcox J, Duffy PR. Is it a ‘senior moment’ or early dementia? Addressing memory concerns in older patients. Current Psychiatry, 2016 May: 15(5): 28-40
10.Livingston G, Huntley J, Sommerlad A, et al. Dementia prevention, intervention, and care: 2020 report of the Lancet Commission. Lancet. 2020;396(10248):413-446.
11.Yu JT, Xu W, Tan CC, et al. Evidence-based prevention of Alzheimer's disease: systematic review and meta-analysis of 243 observational prospective studies and 153 randomised controlled trials. J Neurol Neurosurg Psychiatry. 2020;91(11):1201-1209
12.Frisoni GB, Molinuevo JL, Altomare D, et al. Precision prevention of Alzheimer's and other dementias: Anticipating future needs in the control of risk factors and implementation of disease-modifying therapies. Alzheimers Dement. 2020;16(10):1457-1468.
13.World Health Organization (WHO). Risk reduction of cognitive decline and dementia. WHO Guidelines. www.who.int/mental_health/neurology/dementia/guidelines_risk_reduction/en. Accessed April 16, 2021.