Dementia can have a genetic component, but it is not solely determined by genetics. There are different types of dementia, and the role of genetics can vary among them.

1. **Alzheimer's Disease**: This is the most common form of dementia. There are two types of Alzheimer's: early-onset and late-onset.

• **Early-Onset Alzheimer's** (which occurs before age 65) is often linked to specific genetic mutations in genes such as APP, PSEN1, and PSEN2. If a person inherits one of these mutations, they have a very high likelihood of developing the disease.
• **Late-Onset Alzheimer's** (which occurs after age 65) has a more complex genetic component. The APOE ε4 allele is a well-known risk factor; having one or two copies of this allele increases the risk of developing Alzheimer's, but it does not guarantee it.

2. **Other Types of Dementia**: Other forms of dementia, such as frontotemporal dementia and vascular dementia, may also have genetic factors, but the inheritance patterns can be less clear. Some cases of frontotemporal dementia are linked to mutations in specific genes, while vascular dementia is more influenced by lifestyle and health factors, such as cardiovascular health.

3. **Family History**: Having a family history of dementia can increase an individual's risk, but it is important to note that many people with a family history do not develop dementia, and many who do have no family history.

4. **Environmental and Lifestyle Factors**: Genetics is just one piece of the puzzle. Environmental factors, lifestyle choices (such as diet, exercise, and smoking), and overall health also play significant roles in the development of dementia.

In summary, while there is a genetic component to some types of dementia, it is not the only factor, and many individuals with a genetic predisposition may never develop the condition.