Understanding Dementia: Types, Symptoms, and Care Approaches

Understanding dementia（認知症の理解）· Material

認知症の理解とケア · Updated 26 October 2026

認知症 is not a normal part of ageing; it is a set of symptoms caused by disease or damage to the brain that interferes with daily life. Questions in the 認知症の理解 field often ask you to identify the type of dementia from a case excerpt, so this article stresses the distinctive features of each type and how to respond in care.

Core symptoms and BPSD

Symptoms are divided into two groups. Core symptoms （中核症状） arise directly from brain damage: memory impairment （記憶障害）, especially of short-term memory; disorientation （見当識障害） to time, place, and person; reduced understanding and judgement; and impaired executive function （実行機能障害）, such as being unable to plan the steps of cooking. In some cases there are also language impairment （失語）, 失行， and 失認.

Behavioural and psychological symptoms (BPSD, 行動・心理症状） appear as reactions to the core symptoms and the environment: anxiety, wandering （徘徊）, agitation, the delusion that belongings have been stolen （もの盗られ妄想）, and sleep disturbance. BPSD is strongly influenced by physical condition (pain, constipation, dehydration), the environment, and how staff communicate — so BPSD can be reduced far more by the right approach than core symptoms can.

• 中核症状： memory, orientation, judgement, executive function
• BPSD: behavioural and psychological, influenced by the environment and staff approach

The four main types of dementia

アルツハイマー型 is the most common. It begins slowly with forgetting recent events （近時記憶障害） and progresses gradually and continuously. 血管性 is caused by cerebrovascular problems such as infarction; it progresses in steps （階段状） with each repeated episode, and abilities are lost unevenly （まだら認知症） — some functions are damaged while others remain intact — together with neurological symptoms depending on the site of the damage.

レビー小体型 is marked by vivid visual hallucinations （幻視）, Parkinson-like symptoms （パーキンソン症状）, and fluctuations in alertness and thinking within a single day. 前頭側頭型 appears at a relatively younger age; personality and behaviour change before forgetfulness does — for example loss of self-control （脱抑制） and repetitive behaviours.

• Alzheimer's: starts with short-term forgetfulness, progresses slowly and evenly
• Vascular: stepwise pattern, abilities lost in patches （まだら）
• Lewy body: 幻視 + Parkinson symptoms + fluctuations
• Frontotemporal: prominent personality and behaviour change

Care principles: person-centered care

パーソン・センタード・ケア (person-centered care), proposed by Tom Kitwood, sees a person with dementia as a whole individual with a life history, habits, and feelings of their own — not merely a bundle of symptoms. Staff try to see the world from that person's point of view.

In practice: do not flatly deny or correct their delusions — first accept the feeling behind them; keep familiar routines and surroundings so they do not become confused; make use of abilities that remain and of long-term memory, which is relatively preserved (for example through 回想法， reminiscence therapy); and say one thing at a time in short sentences. When BPSD appears, look for physical and environmental causes first before treating it as "a symptom to be suppressed".

• See the person, not just the symptoms (person-centered care)
• Accept the feeling behind a delusion; do not confront it head-on
• For BPSD: check pain, constipation, environment, and how we speak

Key terms

Frequently tested points

• A case with 幻視 and Parkinson symptoms is almost certainly レビー小体型.
• Stepwise progression + unevenly lost abilities = 血管性.
• Personality change and loss of self-control coming before forgetfulness = 前頭側頭型.
• もの盗られ妄想 is a delusion typical of dementia, especially Alzheimer's — the right response is to accept the feeling, not to deny it.

Independent study material for the Japanese national Certified Care Worker exam (介護福祉士国家試験). Official terms and rules may change — always cross-check with the latest official sources.