Types of Alzheimer’s disease
Last Reviewed: Jul 2, 2025In order to understand familial Alzheimer’s disease (FAD), it helps to understand a bit about Alzheimer’s disease overall.
Are dementia and Alzheimer’s disease the same thing?
No. Many people think dementia and Alzheimer's disease are the same thing, but they're not.
Dementia is a general label (or umbrella term) for problems with memory, thinking, or other brain functions that interfere with daily life. Dementia is not a disease itself. It refers to a group of symptoms. There are many types of dementia, and it can be caused by progressive neurological diseases as well as non-neurological conditions.
Alzheimer's disease is the most common cause of dementia. It is a progressive neurodegenerative disease characterized by the presence of amyloid plaques and neurofibrillary tangles in the brain. It is a specific disease, whereas dementia is a group of conditions.
Learn more about the differences between dementia and Alzheimer’s disease.
Late onset vs early onset Alzheimer’s disease
Generally speaking, the biggest risk factor for Alzheimer’s is age. As people get older, their risk of developing the disease increases. But families impacted by FAD genetics know that Alzheimer’s disease does not exclusively affect older people.
Late-onset Alzheimer's disease (LOAD)
Late-onset Alzheimer’s disease (LOAD) is the most common type of AD, representing around 90% of Alzheimer’s cases. LOAD occurs in people after the age of 65.
Early-onset Alzheimer's disease (EOAD)
Early-onset Alzheimer’s disease (EOAD) is less common than LOAD, and occurs in less than 10% of Alzheimer’s cases.¹
People with EOAD experience symptoms before age 65, and the disease often progresses more quickly and aggressively than the late-onset form of the disease.
Because EOAD is not very common, people dealing with this early type of the disease often go through a long and difficult process to get the right diagnosis. A small portion of EOAD cases (~10%) are caused by mutations in APP, PSEN1, and PSEN2, while the rest remain unexplained.²
Sporadic vs familial Alzheimer’s disease
In addition to late vs early onset, cases of Alzheimer’s disease can be classified as either sporadic or familial.
Sporadic Alzheimer's disease
Sporadic Alzheimer’s disease is the most common type. Symptoms usually appear in people over age 65, but can start earlier. Scientists believe that sporadic Alzheimer’s is caused by a combination of age-related changes, lifestyle factors, environmental factors and/or genetic variants (like one copy of APOE4).
Familial Alzheimer's disease
Familial Alzheimer's disease (FAD), also sometimes referred to as autosomal dominant Alzheimer’s disease (ADAD), is caused by mutations in the APP, PSEN1, or PSEN2 genes. People with FAD mutations typically present symptoms of disease between 40-50 years of age, but some mutations can cause symptom onset in people as early as their 20s or as late as their 70s. Although FAD represents less than 1% of all Alzheimer’s disease cases³, it feels anything but rare to the families it impacts.
About 45,000 people worldwide are affected by FAD. This rarity can make it hard for families to get the right diagnosis. Many family doctors and some neurologists are not familiar with FAD. If you're having trouble getting diagnosed, contact Youngtimers for information.
Learn more about diagnosing FAD
You are not alone
The Youngtimers community is full of other families who face FAD. Youngtimers provides programs to help people in this community learn and connect with one another.
Sources
Reitz C, Rogaeva E, Beecham GW. Late-onset vs nonmendelian early-onset Alzheimer disease: a distinction without a difference? Neurol Genet. 2020;6:e512.
Sirkis DW, Bonham LW, Johnson TP, La Joie R, Yokoyama JS. Dissecting the clinical heterogeneity of early-onset Alzheimer's disease. Mol Psychiatry. 2022 Jun;27(6):2674-2688. doi: 10.1038/s41380-022-01531-9. Epub 2022 Apr 7. PMID: 35393555; PMCID: PMC9156414.
Bateman RJ, Aisen PS, De Strooper B, Fox NC, Lemere CA, Ringman JM, Salloway S, Sperling RA, Windisch M, Xiong C. Autosomal-dominant Alzheimer's disease: a review and proposal for the prevention of Alzheimer's disease. Alzheimers Res Ther. 2011 Jan 6;3(1):1. doi: 10.1186/alzrt59. PMID: 21211070; PMCID: PMC3109410.