What Causes Dementia

I still remember the day I realized that my mother’s forgetfulness wasn't just part of aging — it was a sign of something deeper. As we traveled through the countryside, she would suddenly pause mid-step, her eyes scanning the horizon like she was searching for a memory that had slipped through her fingers. This wasn't just a moment of confusion — it was a living, breathing reminder of what causes dementia, a condition that affects millions of people worldwide and can strike without warning.

In the years since that day, I've learned that dementia is not a single disease but a group of conditions, each with its own set of causes and symptoms. Whether it's Alzheimer’s, vascular dementia, or something else entirely, the impact on a person's life — and their loved ones — can be profound. Understanding what causes dementia is the first step in learning how to navigate this complex and often confusing journey, whether you're planning a trip with a loved one or simply seeking knowledge.

Traveling with someone who has dementia can be challenging, but it's also deeply rewarding. It teaches you to slow down, to notice the small details that others might overlook, and to find beauty in the unexpected. As I've walked through quiet villages and listened to the sound of wind chimes in a foreign town, I've come to understand that the causes of dementia are as varied as the landscapes we’ve explored — and that every journey, no matter how small, can be a source of comfort and connection.

Genetic Factors in Dementia

As of September 2026, I’ve met several people whose families have a history of dementia, and they often ask if this is a guarantee of their own future. The truth is, while genetics can increase the risk, it’s not the only factor at play. For example, one family member I spoke to had a genetic predisposition but maintained an active lifestyle and stayed socially engaged, which may have delayed the onset of symptoms.

Studies have shown that people with a first-degree relative who has Alzheimer’s are more than twice as likely to develop the disease themselves. However, this doesn’t mean it’s inevitable — lifestyle choices and environmental factors can still make a difference.^[1]

I once traveled with a group of researchers who were studying how genetic markers interact with lifestyle factors in older adults. Their findings suggested that even with a genetic risk, those who maintained physical activity, a healthy diet, and strong social connections had a lower incidence of dementia than those who did not.

Part of our More dementia caregivers guide.

Lifestyle and Environmental Influences

During one of my travels, I met an elderly man who had lived in a city with high levels of pollution for most of his life. He shared with me that he had always believed that his cognitive decline was a natural part of aging. Upon learning about the link between air quality and brain health, he felt a sense of relief — it was something he could address.

Research has shown that long-term exposure to air pollution, particularly fine particulate matter, may increase the risk of developing dementia. Similarly, a sedentary lifestyle, poor nutrition, and chronic stress are all linked to a higher risk of cognitive decline.^[2]

One of the most powerful things I’ve learned from my travels is that small changes can have a big impact. Eating a diet rich in antioxidants, getting enough sleep, and managing stress through mindfulness practices can all help protect the brain over time.

A healthy lifestyle can be one of the strongest defenses against dementia.

Related: Early onset dementia

The Role of Infections and Immune System Health

I once spoke with a nurse who had cared for patients with dementia, many of whom had a history of untreated infections. She shared that in some cases, these infections may have contributed to the progression of the disease by causing chronic inflammation in the brain.

Research has found that infections such as herpes, syphilis, and HIV can increase the risk of dementia. Inflammation caused by these infections can damage brain cells over time, leading to cognitive impairment.^[3]

One of the most surprising discoveries I made during my travels was learning about a study that showed how treating infections early can reduce the risk of dementia. This is a reminder that taking care of our overall health is crucial for brain health as well.

“I still remember the day I realized that my mother’s forgetfulness wasn't just part of aging — it was a sign of something deeper.”— Traveling with Dementia Care editors

Related: Alzheimer s icd 10

Neurodegenerative Diseases and Brain Changes

On one of my trips, I met a woman who had been diagnosed with Alzheimer’s. She described how the disease had slowly taken over her life, making it difficult to remember simple tasks like cooking or managing her finances. Her story was both heartbreaking and eye-opening.

Alzheimer’s is the most common cause of dementia, and it involves the buildup of abnormal proteins in the brain that destroy nerve cells. Other forms of dementia, such as vascular dementia, are caused by damage to the brain’s blood vessels.

Understanding the brain changes that occur in dementia can help loved ones better support those who are affected. It also highlights the importance of early detection and treatment to slow the progression of the disease.

Related: Clinical dementia rating scale

The Impact of Trauma and Brain Injury

During one of my travels, I spoke with a man who had suffered a head injury in his youth. He shared that he had always thought the injury was behind him, but in his 60s, he began experiencing memory problems that led to a diagnosis of dementia. His story highlights how past injuries can have long-term effects.

Research has shown that even a single episode of severe head trauma can increase the risk of dementia. Repetitive brain injuries, such as those seen in athletes, are also linked to a higher risk of cognitive decline.

This is a sobering reminder that protecting the brain from injury is important at every stage of life. If you or a loved one has a history of head injuries, it’s worth discussing with a healthcare professional how to monitor for signs of dementia.

Related: Delirium vs dementia

Diet, Nutrition, and Dementia Risk

On my travels, I visited a village where the local diet was rich in vegetables, fish, and olive oil. I was fascinated to learn that residents there had lower rates of dementia compared to other regions. This led me to explore the connection between diet and brain health further.

Studies have shown that the Mediterranean diet, which emphasizes whole grains, fruits, vegetables, and healthy fats, is associated with a reduced risk of dementia. Similarly, diets high in antioxidants and omega-3 fatty acids may help protect the brain.

One of the most practical things I’ve learned from my travels is that small dietary changes can make a big difference. Incorporating more brain-healthy foods into your daily meals is a simple yet powerful way to support cognitive function.

What you eat today can shape your brain’s future.

Related: Alzheimer s dementia icd 10

The Importance of Social Engagement

While traveling, I met many people who had made it a point to stay socially active, whether through joining local clubs, attending religious services, or simply spending time with friends and family. Their stories were inspiring and showed the power of human connection.

Research has found that people who maintain strong social connections are less likely to develop dementia. Social interaction helps build cognitive reserve — the brain’s ability to cope with damage — and can delay the onset of symptoms.

One of the most valuable lessons I’ve learned is that social engagement isn’t just about quantity — it’s about quality. Meaningful conversations, shared experiences, and emotional support are all essential for brain health.

What Causes Dementia