What Is Alzheimer’s Disease? Understanding Its Causes

Understanding the Alzheimer's Disease : Defining What It Is and It's Causes

It’s Not Just Forgetfulness…

Misplacing your keys, forgetting a name, or missing a bill payment occasionally happens to most people. It does not automatically mean something is wrong. Our brains naturally forget things when we become distracted, tired, stressed, or simply have too much on our minds. But sometimes, those everyday slips begin to look and feel different.

A parent might start asking the exact same question several times during a single conversation, a spouse may become genuinely confused on a familiar route they have taken for years, or someone who has always managed their work well may suddenly struggle with familiar tasks.

Sometimes the individual notices these changes first, while other times a family member or close friend picks up on the shift. Either way, something feels fundamentally different, and one possible reason behind those changes is Alzheimer’s disease.

Alzheimer’s disease is the most common cause of dementia.

In the United States, approximately 7.4 million adults aged 65 and older are living with Alzheimer’s disease- about 1 in 9 people in that age group. Without major advances in prevention or treatment, that number could rise to approximately 13.8 million by 2060. Worldwide, more than 55 million people live with dementia from all causes, with a reported annual cases reaching almost 10 million.

7.4 M

US adults aged 65+ living with Alzheimer’s

1 in 9

People aged 65 and older in the US

55M +

People worldwide live with dementia from all causes

For many families, the initial signs may seem minor or easy to dismiss at first, meaning that by the time the changes become obvious, the disease may already have been developing inside the brain for years. Fortunately, our scientific understanding of Alzheimer’s has changed considerably. Researchers now understand much more clearly what happens at a biological level, doctors have better ways of detecting the disease, and newer treatments can slow its progression in some people.

To make sense of this condition, it helps to look closely at what Alzheimer’s actually is, how it differs from normal ageing, what is happening inside the brain, and how modern medicine approaches diagnosis and care.

What Is Alzheimer's Disease?

Alzheimer’s disease is a progressive disease of the brain that gradually affects memory, thinking, behavior, communication, and the ability to manage everyday activities. While the risk of developing the condition increases as people get older, Alzheimer’s is not simply a normal part of getting older.

It is also much broader than simple memory loss. People experience Alzheimer’s in different ways. For some people, memory problems appear first, manifesting as forgetting recent conversations or events, repeating questions or stories, misplacing things and being unable to retrace their steps, or relying much more heavily on notes, reminders, or other people.

For others, the initial signs may involve finding familiar words, following a recipe or completing a familiar task, managing money, bills, or medication, navigating familiar places, planning, decision-making, or problem-solving, keeping up with work or social activities, or changes in mood, personality, and behavior.

These changes affect more than a person’s ability to complete tasks. Someone may feel deep frustration because a task that used to be easy suddenly takes much more effort, alongside embarrassment when they cannot find a word or remember something they once knew easily. There may also be anxiety or uncertainty about what is happening.

Families can have their own difficult experiences, frequently balancing worry, exhaustion, guilt, or simply feeling unsure about how to help. Some people recognize that something is changing, while others may not.

A diagnosis can bring mixed feelings too, offering a relief of having an explanation for years of confusing changes while bringing fear and uncertainty about what comes next. There is room for all of those reactions.

What Happens in The Brain?

To understand Alzheimer’s, it helps to look at what happens inside the brain as the disease progresses. Two abnormal protein build-ups play central roles in this process. One forms sticky plaques between brain cells, while the other forms tangles inside the cells themselves. As these changes build up over time, communication between brain cells breaks down, eventually leading to permanent cell damage.

To picture how this unfolds, imagine the brain as a bustling city where brain cells act as individual neighborhoods and the connections between them function as roads and communication networks. Information must move continuously along these routes for a person to remember, speak, plan, recognize faces, make decisions, and manage everyday activities.

In Alzheimer’s, the plaques act like debris blocking the streets between neighborhoods, making communication harder. The tangles are more like system failures developing inside the houses themselves, disrupting how the neighborhoods run. At first, the brain finds clever workarounds, like taking longer to recall a name or relying more heavily on digital reminders.

Eventually, however, as the damage spreads to more areas of the city, those workarounds stop being enough.

As people live longer, the number of people living with dementia is expected to increase. Prevalence rates also vary across different populations. Women are diagnosed with dementia more often than men, partly because women tend to live longer. Differences between racial and ethnic groups are also shaped by factors such as cardiovascular health, education, healthcare access, and income.

Ultimately, Alzheimer’s is not caused by one protein, one gene, or one behavior. It develops through a complicated combination of age, genetics, biology, health, lifestyle, and environmental factors.

How is Alzheimer's Different From Normal Ageing?

Every brain changes with age. You may take longer to learn something new, a person’s name may temporarily escape you, or multitasking may not feel quite as easy as it once did. During normal ageing, however, memory lapses are usually occasional, everyday responsibilities remain manageable, and lists, calendars, reminders, or extra time are usually enough to let the person compensate for the lapse.

With Alzheimer’s, changes tend to become more frequent and disruptive. People begin struggling consistently with managing finances, taking medication correctly, cooking or shopping, driving safely, completing work responsibilities, navigating familiar places, maintaining normal social activities, or following familiar routines.

The more useful question is not whether someone occasionally forgets something, but whether the changes are becoming more frequent and interfering with everyday life. Memory problems do not automatically mean Alzheimer’s.

Conditions like depression, anxiety, poor sleep, medication side effects, thyroid problems, vitamin deficiencies, infections, hearing or vision loss, strokes, and other medical conditions can affect memory and thinking too.

A proper medical assessment matters. Sudden confusion is also different from the gradual changes usually associated with Alzheimer’s, as rapid confusion can have other causes including infection, medication problems, stroke, or another urgent medical condition, and should be assessed promptly.

Normal Ageing

Possible Alzheimer's

Why Does Alzheimer's Happen?

There is no single cause. Age is the strongest known risk factor, and the likelihood of Alzheimer’s increases considerably after age 65. Genetics also plays a role.

You might hear about a specific gene variant called APOE epsilon 4, which is common in late-onset Alzheimer’s.

Having one copy raises your risk, and having two copies raises it even more. But a genetic risk is never a guarantee. Plenty of people carry that gene and never get Alzheimer’s, while others who do not have it still develop the disease. There are also rare, inherited genetic mutations (sudden changes that occur in our genes) that can cause early-onset Alzheimer’s in certain families before age 65, but those cases are quite uncommon.

Beyond age and genetics, researchers have linked several everyday health and lifestyle factors to a higher risk of dementia. While having any of these does not mean Alzheimer’s is inevitable, managing them can help protect your overall brain health:

Heart health: High blood pressure, diabetes, high cholesterol, and obesity.
Daily lifestyle habits: Smoking, physical inactivity, heavy alcohol use, and lower educational opportunities.
Senses and Social connection: Hearing loss, untreated vision loss, and social isolation.
General wellbeing: Depression, sleep issues, air pollution, and past head injuries.

Taking care of your heart, staying active, protecting your senses, keeping your mood and sleep in check, and staying socially connected can all help support your overall brain health and lower your risk of developing the disease.

Alzheimer’s may begin long before the first memory is forgotten. As the brain’s natural defense and waste-clearing systems become less effective, inflammation and cellular damage can gradually weaken the connections that allow us to think, remember, and make sense of the world.

Beyond Alzheimer's Diagnosis: Understanding the Person

Alzheimer’s disease changes far more than memory. It can affect relationships, independence, and the everyday experiences that give life its meaning. Yet understanding the condition is only one part of understanding those who live with it.

While research continues to uncover how Alzheimer’s develops and how it might be treated, compassionate care, informed decisions, and meaningful support remain essential. A diagnosis may change someone’s circumstances, but it does not erase their identity, experiences, or need for connection.

At Healthful Heroes, we believe that greater awareness begins when medical knowledge meets human experience. Because behind every diagnosis is a person whose story deserves to be heard, understood, and valued.

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References

Dhana K, Beck T, Desai P, Wilson RS, Evans DA, Rajan KB. Prevalence of Alzheimer’s disease dementia in the 50 US states and 3142 counties: A population estimate using the 2020 bridged-race postcensal from the National Center for Health Statistics. Alzheimers Dement. 2023 Oct;19(10):4388-4395. doi: 10.1002/alz.13081. Epub 2023 Jul 17. PMID: 37458371; PMCID: PMC10593099.
Scheltens P, De Strooper B, Kivipelto M et al., Alzheimer’s disease. The Lancet, 2021; 397, 1577-1590.
Alzheimer’s Association. 2025 Alzheimer’s disease facts and figures. Alzheimers Dement. 2025;21(4):e70235. doi:10.1002/alz.70235.
Cummings J, Apostolova L, Rabinovici GD, et al., Lecanemab: Appropriate use recommendations. J Prev Alzheimers Dis. 2023;10(3):362–377. doi:10.1016/j.tjpad.2023.05.016
Jack CR Jr, Bennett DA, Blennow K, et al., NIA-AA Research Framework: Toward a biological definition of Alzheimer’s disease. Alzheimer’s Dement. 2018;14(4):535–562. doi:10.1016/j.jalz.2018.02.018
Livingston G, Huntley J, Sommerlad A, et al., Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. Lancet. 2024;404(10452):572–628. doi:10.1016/S0140-6736(24)01296-0
McKhann GM, Knopman DS, Chertkow H, et al., The diagnosis of dementia due to Alzheimer’s disease: Recommendations from the National Institute on Aging- Alzheimer’s Association workgroups on diagnostic guidelines for Alzheimer’s disease. Alzheimer’s Dement. 2011;7(3):263–269. doi:10.1016/j.jalz.2011.03.005
Mintun MA, Lo AC, Duggan Evans C, et al., Donanemab in early Alzheimer’s disease. N Engl J Med. 2021;384(18):1691–1704. doi:10.1056/NEJMoa2100708
National Institute on Aging. What Is Alzheimer’s Disease? March, 3 2025. Available at:https://www.nia.nih.gov/health/alzheimers-and-dementia/what-alzheimers-disease. Accessed September 13, 2026.
Palmqvist S, Whitson HE, Allen LA, Suarez-Calvet M, Galasko D, Karikari TK, Okrahvi HR, Paczynski M, Schindler SE, Teunissen CE, Zetterberg H, Carrillo MC, Edelmayer RM, Mahinrad S, McAteer MB, Kahale LA, Pahlke S, Tampi MP. Alzheimer’s Association Clinical Practice Guideline on the use of blood-based biomarkers in the diagnostic workup of suspected Alzheimer’s disease within specialized care settings. Alzheimers Dement. 2025 Jul;21(7):e70535. doi: 10.1002/alz.70535. PMID: 40729527; PMCID: PMC12306682.
Sims JR, Zimmer JA, Evans CD, et al., Donanemab in early symptomatic Alzheimer disease. N Engl J Med. 2023;388(20):1907–1918. doi:10.1056/NEJMoa2302392
van Dyck CH, Swanson CJ, Aisen P, Bateman RJ, Chen C, Gee M, Kanekiyo M, Li D, Reyderman L, Cohen S, Froelich L, Katayama S, Sabbagh M, Vellas B, Watson D, Dhadda S, Irizarry M, Kramer LD, Iwatsubo T. Lecanemab in Early Alzheimer’s Disease. N Engl J Med. 2023 Jan 5;388(1):9-21. doi: 10.1056/NEJMoa2212948. Epub 2022 Nov 29. PMID: 36449413.
World Health Organization. Dementia. July, 3 2026. Available at:https://www.who.int/news-room/fact-sheets/detail/dementia. Accessed September 13, 2026.

Nothing on this page is medical advice. Always discuss your options with your own care team.

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