Dementia, a neurocognitive disorder, refers to a range of progressive mental and behavioral changes caused by cerebrovascular or neurological diseases that permanently damage the brain by impairing the activity of brain cells. These changes can affect memory, speech, reasoning, and the ability to perform the activities of daily living. Dementia is one of the leading causes of disability and dependency among older people worldwide.
Occasional forgetfulness and memory lapses are not signs of dementia. Dementia is caused by disease and is not the inevitable result of growing older. It is distinct from normal age-related cognitive decline, such as less efficient short-term memory after age sixty-five. Research indicates that although people with cognitive impairment have an increased risk for dementia, not all people with mild cognitive impairment will progress over time to dementia. Alzheimer's disease (AD), which is the most commonly known dementia, accounts for about 70 percent of all dementia cases. Vascular dementia (also known as multi-infarct dementia) is a neurocognitive disorder that occurs after a stroke or a series of small strokes; it accounts for a significant minority of diagnosed dementia cases.
When the American Psychiatric Association released the fifth edition of its Diagnostic and Statistical Manual of Mental Disorders in 2013, it replaced the commonly known term dementia with mild/major neurocognitive disorder. Neurocognitive disorder is a more precise term for symptoms such as changes in memory and cognition and does not carry the social stigma of the word dementia, which comes from the Latin word dementis, meaning "insane." Even so, many patient and caregiver support organizations, as well as international health organizations and public health programs continue to use the term dementia because neurocognitive disorder is not yet well known by the general public.
Because the number of people with dementia is anticipated to increase as populations age, and older adults with cognitive impairment are at risk for institutionalization, the economic burden for society is expected to escalate. As such, the effort to prevent and treat AD and other dementias is an increasingly important public health issue.
Individuals with dementia typically exhibit a range of symptoms, including memory loss, impaired reasoning abilities, difficulty completing once-routine tasks, alteration of speech patterns, impaired concentration, and personality changes. As the disease progresses, memory loss increases and mood swings are frequent, accompanied by confusion, irritability, restlessness, and problems communicating. Affected people may have trouble finding words, impaired judgment, and difficulty performing even simple, familiar tasks. Some also experience visual, auditory, or olfactory hallucinations. People with severe or advanced cognitive impairment cannot live alone and require supervision and assistance from caregivers.
Research indicates that genetics, diet, and lifestyle factors may influence an individual's risk of developing dementia. Lack of physical activity, vitamin D deficiency, smoking, and social isolation are also linked to cognitive decline among older adults. Individuals with a history of hypertension, obesity, and diabetes may have an increased risk of developing AD or another form of dementia as they age.
With mild neurocognitive disorder, symptoms are usually not severe enough to be known as dementia; daily life is not compromised by two or more symptoms that are associated with cognitive impairment. Usually, the affected older person gradually becomes less aware of memory problems for as long as a few years prior to developing dementia. People who are sufficiently aware to be concerned with memory difficulties are unlikely to be experiencing fulminant dementia. As dementia progresses, cognitive decline becomes more apparent. For example, affected individuals may have limited or no recall of recent activities and may be unable to recall their own address or telephone numbers.
When the disease progresses to severe or late-stage, patients are entirely unable to care for themselves and require around-the-clock care and supervision. They no longer recognize family members, other caregivers, or themselves, and they require assistance with daily activities such as eating, dressing, bathing, and using the toilet. People with AD may become incontinent, blind, completely unable to communicate, and have difficulty swallowing.
Diagnosing and Treating Dementia
Historically, the diagnosis of AD was made by examining the brain tissue of patients who were suspected of dying from the disease. Their brains revealed a pattern that is the hallmark of the disease: tangles of fibers and clusters of degenerated nerve endings in areas of the brain that are crucial for memory and intellect. Current diagnoses of AD and other dementias are based largely on the patient's history of mental decline but also may include analysis of blood, urine, and spinal fluid as well as the use of brain scans (computed tomography and magnetic resonance imaging) to detect strokes or tumors and to measure the volume of brain tissue in the areas that are used for memory and cognition.
AD may begin many years before the first symptoms arise. One of the aims of current research is to diagnose the disease before symptoms appear. Some researchers believe treatment for AD will likely be most effective when it is administered before symptoms appear and before the brain is irrevocably damaged. In June 2019, an international group of investigators reported in the journal JAMA Neurology the development of an accurate blood test that can be used to screen people for AD. If proven effective, physicians may be able to use the test to identify which patients should be referred for further testing and more extensive clinical assessments.
There is no cure for AD, and treatment focuses on managing symptoms. As of mid-2019, there were five drugs approved by the U.S. Food and Drug Administration for the treatment of AD and a sixth drug was available globally. Medication does not slow the progression of the disease, but it may slow the appearance of some symptoms and can lessen others, such as agitation, anxiety, unpredictable behavior, and depression. Physical exercise and good nutrition are important, as is a calm and highly structured environment. The objective is to help patients maintain as much comfort, normalcy, and dignity for as long as possible.
Research about how to prevent AD is underway. One study is testing a drug that targets beta-amyloid, because high levels of beta-amyloid in the brain are known to increase the risk of developing AD. Other research is evaluating the benefit of drug treatment for people who have a genetic mutation that sharply increases the risk for AD but have no symptoms of the disease.
The World Health Organization (WHO) estimates that fifty million people worldwide had dementia in 2018 and that nearly ten million new cases occur every year. About 5.8 million people diagnosed with dementia due to AD live in the United States, and this number is expected to rise to fourteen million by 2050. An estimated 10 percent of people age sixty-five and older have dementia, and every sixty-five seconds someone in the United States develops the disease. In the United States, AD is the fifth-leading cause of death in people ages sixty-five and older; it is responsible for more deaths than breast cancer and prostate cancer combined.
The WHO and Alzheimer's Disease International predict that the number of people living with dementia will increase worldwide. Regions experiencing a demographic shift to an increasingly older population will likely have the most significant increases in dementia cases. The WHO estimates that the global burden of dementia will increase to 82 million affected people by 2030, and will rise to 152 million by 2050. The total global socioeconomic costs of dementia in 2015 were an estimated $818 billion, or 1.1 percent of the total worldwide gross domestic product.
Developing countries are expected to see the largest increases in diagnosed dementia cases over the next several decades. Improvements in sanitation and health care in the world's poorer regions will help more people live into old age, when dementia is the most likely to occur. Better health-care systems in developing nations mean more people will be diagnosed with dementia. According to WHO estimates, by 2040 around three-quarters of dementia cases will occur in the developing world. The economic burden of dementia in developing countries is significant, because affected people are often cared for at home by family caregivers who may have to leave the workforce. Dementia-related costs—from the provision of health care for people with dementia to lost wages of caregivers—are skyrocketing. In 2019, AD and other dementias cost the United States $290 billion, including $195 billion in Medicare and Medicaid payments. By 2050, the costs are projected to be in excess of $1.1 trillion.
The Dementia Research Group, a global network of researchers supported by Alzheimer's Disease International, notes that dementia often goes undiagnosed even in high-income countries. In developing countries, more than 90 percent of people with dementia remain undiagnosed by a physician. Lack of access to routine health care and a lack of physician training in neurocognitive disorders can exacerbate the problem of undetected disease in areas where health-care systems are challenged and populations are underserved. Globally, neurocognitive disorders are likely underreported because family members, caregivers, and even health-care providers often erroneously assume that early symptoms of dementia are normal consequences of aging.