David Perlmutter, M.D.

For decades, one of the most striking and often overlooked features of Alzheimer’s disease is this: it affects women about twice as often as men. Why would that be? Is it simply that women live longer? Hormones? Genetics? Or is something deeper going on inside the brain? A fascinating study published in Communications Biology sheds light on this mystery by focusing on one of the most important players in brain health: microglia, the brain’s resident immune cells.

We tend to think of emojis as harmless, simple digital decorations that soften language, add humor, or clarify tone. But emerging neuroscience suggests something far more consequential. A recent EEG-based study reveals that when we see emojis, whether happy, sad, or angry, the brain processes them using neural pathways strikingly similar to those engaged when we interpret real human facial expressions.

As many of you know, my wife and I recently had the incredible opportunity to visit Antarctica. It is difficult to adequately describe the experience of arriving in a place so vast, so pristine, and so profoundly removed from the rhythms of everyday life. There is an immediate and humbling sense that you are entering one of the last truly wild frontiers on Earth. The scale alone is breathtaking with endless expanses of ice, towering glaciers, and an unfamiliar silence that feels almost sacred.

At first glance, autism and Alzheimer’s disease appear to exist at opposite ends of the neurological spectrum, one a condition of early brain development, the other a disease of later-life degeneration. But as our understanding of brain biology deepens, a compelling unifying idea emerges: these two conditions may, in fact, share a common underlying mechanism.

A fascinating new study explores a topic I have written about many times before: the brain’s waste clearance system, known as the glymphatic system. As I have discussed in previous blogs, one of the most important reasons to get adequate deep sleep is that this is when the glymphatic system is most active. During deep, slow-wave sleep, cerebrospinal fluid washes through the brain and helps clear away metabolic debris, including proteins linked to neurodegenerative diseases.

A recent meta-analysis published in Neurology offers encouraging news: women who closely follow a Mediterranean-style diet appear to have about a 12 percent lower risk of stroke. That finding is important. Stroke remains one of the greatest threats to women’s health. It is the third leading cause of death in women, and about one in five women will experience a stroke in her lifetime. Each year, more women than men suffer strokes and die from them.

A major new study published in JAMA followed more than 131,000 men and women for up to 43 years and offers reassuring news for coffee drinkers. Researchers looked at long-term consumption of caffeinated coffee, decaffeinated coffee, tea, and total caffeine intake. Over the decades of follow-up, more than 11,000 cases of dementia were recorded. Here’s the key takeaway: people who drank caffeinated coffee had a lower risk of developing dementia.

I’m writing this blog while cruising south (upstream) on the Nile River, watching the shoreline drift by in its slow, ancient rhythm. It is impossible to be here and not feel the weight of history. This river has sustained human life for thousands of years. Long before modern medicine, long before industrial agriculture, long before the words “chronic disease” entered our vocabulary, the Nile nourished civilization. Its annual flooding replenished soil. Its waters fed crops. Its fish fed families.

For decades, federal dietary guidance has struggled to keep pace with what clinicians and researchers have observed on the front lines of chronic disease. The newly released Dietary Guidelines for Americans, 2025–2030 represent a meaningful and, frankly, refreshing shift in the right direction. Their central message, “eat real food” is not revolutionary, but it is profoundly important given the metabolic and neurological crisis we now face as a nation.

In my recent lectures, podcasts, and blog posts, I’ve been emphasizing a message that is still surprisingly new to many people: the health of the brain is inseparable from the health of its immune system. At the center of that immune system are specialized cells called microglia. This idea—that microglia are not passive bystanders but active decision-makers that shape brain health across the lifespan—is the central theme of my upcoming book, Brain Defenders.