The course of dementia is often described in four stages that show a pattern of progressive cognitive and functional impairment. However, the use of numeric scales allow for more detailed descriptions. These scales include: the Global Deterioration Scale for Assessment of Primary Degenerative Dementia (GDS or Reisberg Scale), the Functional Assessment Staging Test (FAST), and the Clinical Dementia Rating (CDR). Using the GDS which more accurately identifies each stage of the disease progression, a more detailed course is described in seven stages – two of which are broken down further into five and six degrees. Stage 7(f) is the final stage.
Pre-dementia states include pre-clinical and prodromal stages.
Sensory dysfunction is claimed for this stage which may precede the first clinical signs of dementia by up to ten years. Most notably the sense of smell is lost. The loss of the sense of smell is associated with depression and loss of appetite leading to poor nutrition. It is suggested that this dysfunction may come about because the olfactory epithelium is exposed to the environment. The lack of blood-brain-barrier protection here means that toxic elements can enter and cause damage to the chemosensory networks.
Pre-dementia states considered as prodromal are mild cognitive impairment (MCI), and mild behavioral impairment (MBI).
Kynurenine is a metabolite of tryptophan that regulates microbiome signalling, immune cell response, and neuronal excitation. A disruption in the kynurenine pathway may be associated with the neuropsychiatric symptoms and cognitive prognosis in mild dementia.
In this stage signs and symptoms may be subtle. Often, the early signs become apparent when looking back. 70% of those diagnosed with MCI later progress to dementia. In MCI, changes in the person's brain have been happening for a long time, but symptoms are just beginning to appear. These problems, however, are not severe enough to affect daily function. If and when they do, the diagnosis becomes dementia. They may have some memory trouble and trouble finding words, but they solve everyday problems and competently handle their life affairs.
Mild cognitive impairment has been relisted in both DSM-5, and ICD-11, as mild neurocognitive disorders, – milder forms of the major neurocognitive disorder (dementia) subtypes.
In the early stage of dementia, symptoms become noticeable to other people. In addition, the symptoms begin to interfere with daily activities, and will register a score on a Mini Mental State Examination (MMSE). MMSE scores are set at 24 to 30 for a normal coginitive rating and lower scores reflect severity of symptoms. The symptoms are dependent on the type of dementia. More complicated chores and tasks around the house or at work become more difficult. The person can usually still take care of themselves but may forget things like taking pills or doing laundry and may need prompting or reminders.
The symptoms of early dementia usually include memory difficulty, but can also include some word-finding problems, and problems with executive functions of planning and organization. Managing finances may prove difficult. Other signs might be getting lost in new places, repeating things, and personality changes.
In some types of dementia, such as dementia with Lewy bodies and frontotemporal dementia, personality changes and difficulty with organization and planning may be the first signs.
As dementia progresses, initial symptoms generally worsen. The rate of decline is different for each person. MMSE scores between 6–17 signal moderate dementia. For example, people with moderate Alzheimer's dementia lose almost all new information. People with dementia may be severely impaired in solving problems, and their social judgment is usually also impaired. They cannot usually function outside their own home, and generally should not be left alone. They may be able to do simple chores around the house but not much else, and begin to require assistance for personal care and hygiene beyond simple reminders. A lack of insight into having the condition will become evident.
People with late-stage dementia typically turn increasingly inward and need assistance with most or all of their personal care. Persons with dementia in the late stages usually need 24-hour supervision to ensure their personal safety, and meeting of basic needs. If left unsupervised, they may wander or fall; may not recognize common dangers such as a hot stove; or may not realize that they need to use the bathroom and become incontinent. They may not want to get out of bed, or may need assistance doing so. Commonly, the person no longer recognizes familiar faces. They may have significant changes in sleeping habits or have trouble sleeping at all.
Changes in eating frequently occur. Cognitive awareness is needed for eating and swallowing and progressive cognitive decline results in eating and swallowing difficulties. This can cause food to be refused, or choked on, and help with feeding will often be required. For ease of feeding, food may be liquidized into a thick pure.