Dementia is not a disease. It may be caused by a variety of illnesses or injuries. Mental impairment may range from mild to severe. It may also cause personality changes. Some dementias are progressive. This means they get worse over time. Some dementias are treatable or even reversible. Some experts restrict the term dementia to irreversible mental deterioration. In most cases, dementia is progressive, getting worse over time. Dementia progresses differently in everyone. However, most people experience symptoms of the following stages of dementia. At this stage of dementia, people impacted may need assistance from a loved one or care provider. That’s because dementia may now interfere with daily tasks and activities.