Dementia is not one disease. It is a set of symptoms, including memory loss, slower thinking and changes in behaviour, caused by diseases that damage brain cells; Alzheimer's disease is the most common cause. Diagnosis combines memory tests, blood tests to rule out treatable causes and a brain scan. There is no cure, but medicines, therapy and good care help people live well for years.
What is dementia and what causes it?
Dementia is a syndrome: a group of related symptoms linked to a continuing decline in brain function. The NHS stresses that it is not a single disease and not only about memory; it can affect speech, thinking, mood and behaviour. MedlinePlus adds that dementia "is not a normal part of aging".
The underlying cause is brain cell damage. The NHS explains that many dementia-causing diseases involve an abnormal build-up of proteins that kills nerve cells and shrinks parts of the brain. In Alzheimer's disease the proteins are amyloid, which forms plaques around cells, and tau, which forms tangles inside them; the hippocampus, which forms new memories, is affected early. In vascular dementia reduced blood flow kills cells. In dementia with Lewy bodies, clumps of the protein alpha-synuclein disrupt cells. In frontotemporal dementia, proteins including tau damage the frontal and temporal lobes.
The scale is large. The WHO states that in 2021 "57 million people were living with dementia worldwide", with nearly 10 million new cases a year and over 60% living in low- and middle-income countries. Alzheimer's disease may contribute 60 to 70% of cases. For India, a 2023 study from the Longitudinal Aging Study in India (LASI-DAD), published in Alzheimer's & Dementia, estimates a prevalence of 7.4% among people aged 60 and over, about 8.8 million people.
Some causes are reversible. MedlinePlus lists thyroid hormone imbalance, low vitamin B12, abnormal blood sugar, sodium or calcium, certain medicines, normal pressure hydrocephalus, brain tumours and some infections as conditions that cause dementia-like symptoms and may improve with treatment if found early.
What are the main types of dementia?
Four diseases cause most dementia, and many older people have more than one; the NHS says vascular dementia with Alzheimer's is the most common "mixed" combination. The table draws on the NHS pages for each condition.
| Type | What happens in the brain | Typical first symptoms | Typical age | Course |
|---|---|---|---|---|
| Alzheimer's disease | Amyloid plaques and tau tangles; low acetylcholine; hippocampus shrinks early | Forgetting recent events and names, repeating questions, getting lost, trouble with money | Mostly over 65 | Gradual, steady decline |
| Vascular dementia | Small vessel disease, a stroke or repeated mini strokes reduce blood flow | Slowed thinking, poor planning and concentration, mood change; memory loss may be less obvious early | Rare under 65; about 180,000 people in the UK | Can start suddenly; often worsens in steps with stable periods |
| Dementia with Lewy bodies | Lewy body protein clumps in areas controlling thinking, vision and movement | Alertness that fluctuates over minutes or hours, visual hallucinations, slowed movement, acting out dreams, falls and fainting | Rare under 65 | Slow over several years; NHS cites 5 to 7 years average survival after diagnosis |
| Frontotemporal dementia | Abnormal protein clumps shrink the frontal and temporal lobes; often a genetic link | Personality change, loss of empathy, impulsive or socially inappropriate behaviour, or language difficulty; memory affected later | Most diagnosed at 45 to 65 | NHS cites 8 to 10 years average survival from symptom onset |
Who is at risk of dementia?
Age is the biggest risk factor. MedlinePlus calls ageing "the biggest risk factor for dementia", and the NHS reports that 1 in 11 people over 65 in the UK have dementia. The Indian LASI-DAD study shows the same gradient: prevalence of about 2.9% at ages 60 to 64, 10.3% at 70 to 74, 16.3% at 80 to 84 and 25.4% at 85 and over.
Many other risks can be changed. The WHO fact sheet lists them in three groups:
- Health conditions: high blood pressure, diabetes, overweight or obesity, depression, vision and hearing loss, poor sleep, traumatic brain injury and stroke.
- Lifestyle: tobacco smoking, harmful alcohol use, physical inactivity, social isolation and low education.
- Environment: air pollution.
MedlinePlus adds a close family member with dementia, and the NHS says frontotemporal dementia is more likely than other types to run in families.
The Indian data show how education and place shape risk. In the LASI-DAD study, prevalence was 10.3% among people with no formal schooling versus 1.5% among those with middle school or more, and 8.4% in rural areas versus 5.3% in urban areas. Women had higher prevalence than men (9.0% versus 5.8%), though after adjusting for age and education the difference was not statistically significant.
The WHO's advice follows from the list: stay physically and mentally active, do not smoke, avoid harmful drinking, eat a balanced diet, control blood pressure, cholesterol and blood sugar, and use hearing aids when needed. The WHO states there is no cure, so lowering risk is the main lever available.
What are the symptoms of dementia?
The first symptoms are usually small lapses that worsen over months. The NHS lists memory loss, trouble concentrating, difficulty with familiar daily tasks, struggling to follow a conversation or find the right word, confusion about time and place, and mood changes. The WHO notes that mood and behaviour changes, such as anxiety, sadness, anger or withdrawal, can come before memory problems.
Mild problems that do not yet interfere with daily life are called mild cognitive impairment (MCI). The NHS and MedlinePlus both say that not everyone with MCI develops dementia, and the NHS notes that MCI caused by depression, anxiety or thyroid problems often clears when the cause is treated.
Symptoms differ by type, as the comparison table above shows: repeated questions in Alzheimer's, stepwise slowing in vascular dementia, hallucinations and fluctuating alertness in Lewy body dementia, personality change in frontotemporal dementia.
In the later stages the NHS describes severe memory loss, including not recognising close family, loss of speech in some people, reduced mobility, incontinence, weight loss and swallowing difficulty that can cause choking and chest infections. Behavioural and psychological symptoms, including agitation, wandering, aggression and hallucinations, affect a significant number of people late in the illness.
Call 112 or go to an emergency department the same day if confusion starts suddenly over hours, or comes with one-sided weakness, facial drooping, slurred speech, fever or a fall with a head injury. The NHS says stroke-like symptoms require urgent attention, and MedlinePlus notes that delirium from infection or medicines can mimic dementia and is treatable.
How is dementia diagnosed?
Diagnosis starts with a doctor, a memory test and blood tests, and continues with a specialist and a brain scan if needed. The NHS recommends that someone who knows you well comes to the first appointment, because a relative often notices changes the person does not.
The first steps rule out treatable causes. The NHS lists depression and anxiety, delirium from infection, an underactive thyroid and medicine side effects as causes of memory problems. MedlinePlus details the usual blood tests: thyroid function including TSH, vitamin B12, glucose, electrolytes, calcium, kidney function and a full blood count to check for anaemia. Indian prices are in our thyroid test cost guide. A short memory or cognitive test is done at the same visit.
If other causes are excluded, the NHS says the GP refers to an old-age psychiatrist, a geriatrician or a neurologist, often in a memory clinic, for more detailed memory tests and a CT or MRI brain scan. The scan looks for strokes, bleeding, tumours, hydrocephalus and the pattern of shrinkage that points to a type. Prices are in our MRI scan cost guide.
Diagnosis can take time. The NHS says dementia "can be difficult to diagnose, especially if your symptoms are mild", and cites a survey finding that 1 in 4 people wait 2 years before seeking help. In India, a psychiatrist or neurologist at a medical college or large hospital runs the memory clinic.
How is dementia treated?
Treatment relieves symptoms and treats what can be treated; the NHS states "There is currently no cure for dementia." MedlinePlus adds that stopping or changing medicines that worsen confusion is part of treatment.
Medicines for Alzheimer's. The NHS describes acetylcholinesterase inhibitors (donepezil, rivastigmine, galantamine) for mild to moderate Alzheimer's, donepezil also for severe disease, and memantine for moderate or severe Alzheimer's or when the first group is not tolerated. They may also help dementia with Lewy bodies, Parkinson's disease dementia and mixed dementia. The benefit is modest. A 2018 Cochrane review by Birks and Harvey pooled 30 studies with 8,257 participants: donepezil 10 mg improved the ADAS-Cog cognitive score by 2.67 points on a 70-point scale and the MMSE by about 1 point over 6 months, with adverse events in 72% versus 65% on placebo.
Newer anti-amyloid drugs. MedlinePlus says drugs that reduce amyloid may slow early Alzheimer's but carry serious side effects. No Indian source we found describes availability.
Vascular dementia. The NHS says there is no cure but treating blood pressure, cholesterol and clot risk, stopping smoking and exercising may slow further damage.
Behaviour and mood. Coping strategies come first. The NHS says antipsychotics such as risperidone are reserved for persistent aggression or extreme distress, at the lowest dose for the shortest time, reviewed at least every 6 weeks, and prescribed by a consultant psychiatrist.
Therapies. The NHS lists cognitive stimulation therapy, cognitive rehabilitation with an occupational therapist, and reminiscence or life story work as evidence-based ways to improve mood and function.
How many people in India have dementia?
About 8.8 million Indians aged 60 and over have dementia, according to the 2023 LASI-DAD study by Lee and colleagues in Alzheimer's & Dementia. The authors estimate a prevalence of 7.4% (95% confidence interval 6.35 to 8.51) and project around 16.9 million cases by 2036 if prevalence stays the same.
The estimate comes from the Longitudinal Aging Study in India, with fieldwork from 2017 to 2019. An in-depth subsample of 4,096 people aged 60 and over completed a neuropsychological battery and an informant interview; 2,528 were rated by panels of three to four trained clinicians, and dementia was defined as a Clinical Dementia Rating of 1 or more. Those ratings trained a model that imputed dementia status for the remaining 28,949 respondents.
State figures range from 4.5% in Delhi to 11.0% in Jammu and Kashmir, with most of the variation explained by age, education and rural residence rather than by the state itself. Prevalence is higher in rural India (8.4%) than in cities (5.3%), and far higher among people with no formal schooling (10.3%) than among those who completed middle school (1.5%).
The authors note limits: only about 13% of the sample aged 60 and over had the in-depth assessment, state estimates carry wide confidence intervals, and remote rating may have overestimated borderline cases. Even so, it is the first nationally representative estimate for India, and it implies that most families will meet dementia in a parent or grandparent. Earlier Indian figures using other methods are not comparable, so we have not quoted them.
What support is there for caregivers?
Most dementia care in India is given at home by family, and the burden is heavy. The WHO fact sheet reports that informal carers account for about 50% of the global cost of dementia, provide on average 5 hours of care and supervision a day, and that women provide 70% of care hours. WHO's iSupport programme offers free online self-help training for carers.
Practical support starts with the care team. The NHS says that after diagnosis the team should explain the type of dementia, likely progression, treatments, local services and support groups, and the effects on driving and work, and should name a coordinator for ongoing support.
At home, MedlinePlus advises making the house safe, and helping with memory loss, behaviour and sleep problems. Useful steps:
- Keep a written daily routine and a visible clock and calendar.
- Remove loose rugs, fit grab bars and lock away medicines and cleaning products.
- Arrange respite: a relative or paid attendant who covers set hours each week so the main carer rests.
- Watch the carer's own health; depression in carers is common and treatable, and a psychiatrist can help.
Plan early for legal and financial decisions while the person can still take part. The NHS suggests using follow-up visits to discuss powers of attorney and advance statements about future care; in India the equivalent conversations cover bank mandates, property and who will decide on hospital care. This guide is general information from the sources listed below, not medical advice; a registered doctor makes decisions with you.
