Women showed higher amyloid plaque burden, yet similar cognitive decline
At the intersection of two of neurology's most consequential diseases, a Mayo Clinic study presented in 2026 has uncovered a quiet asymmetry: women living with Parkinson's disease carry a measurably heavier burden of Alzheimer's-associated amyloid plaques in their brains than men do, even after accounting for genetic risk. Yet the mind, in its resilience or its mystery, does not seem to register this difference — cognitive outcomes between the sexes remain strikingly similar. The finding invites a deeper reckoning with what brain pathology truly means, and whether the marks left on tissue always tell the story we expect.
- Women with Parkinson's disease were found to have amyloid plaque burdens nearly 17 percentage points higher than men — and remained more than twice as likely to carry heavy pathology even after controlling for age and genetics.
- The disconnect is unsettling: greater biological damage in women's brains did not translate into greater cognitive decline, leaving researchers without a clear explanation for why the pathology and the symptoms refuse to align.
- The study's sample of 230 autopsy-confirmed Parkinson's cases is large enough to surface the disparity but too small to rule out cognitive differences that a broader investigation might reveal.
- Scientists are now pointing toward hormonal, immunological, and genetic mechanisms as possible explanations for women's heightened amyloid susceptibility — none of which are yet understood.
- The lead researcher is calling for larger clinicopathological studies to determine whether this sex-linked vulnerability is a warning signal, a biological quirk, or evidence that the brain's resilience operates differently across sexes.
At the 2026 European Academy of Neurology Congress, Mayo Clinic Arizona researchers presented findings that complicate how scientists understand the overlap between Parkinson's and Alzheimer's disease — and suggest that sex may be a crucial variable. The study drew on 230 people with autopsy-confirmed Parkinson's disease, all participants in a long-running Arizona aging and brain donation program who had undergone yearly clinical evaluations during their lives.
The postmortem brain examinations revealed a clear disparity: women with Parkinson's had significantly higher amyloid plaque burdens than men. Average cortical plaque scores were 6.5 for women versus 4.9 for men, and more than half of women — 56.8 percent — met the threshold for high plaque burden, compared to 39.7 percent of men. Even after adjusting for age at death and the APOE ε4 gene, a major Alzheimer's risk factor, women remained more than twice as likely to carry substantial amyloid accumulation.
What confounded the researchers was what came next. Despite the heavier pathological load, women and men showed no meaningful differences in rates of Alzheimer's dementia or in cognitive test performance during life. Lead author Dr. Erika Driver-Dunckley named the paradox plainly: the biology and the symptoms were not speaking the same language.
Driver-Dunckley suggested the study's sample size may have been too small to detect subtler cognitive differences, and that the relationship between amyloid accumulation and cognitive decline may be more complex than assumed — shaped by resilience, protective factors, or mechanisms not yet identified. The pattern mirrors findings in Alzheimer's disease alone, where women have also shown more severe pathology, hinting at a broader sex-linked biological susceptibility.
The researchers are calling for larger studies to replicate the findings and investigate the underlying mechanisms — hormonal, genetic, or immunological — that might explain why women accumulate more amyloid, and why that accumulation does not always exact a cognitive toll.
At the European Academy of Neurology Congress in 2026, researchers from Mayo Clinic Arizona presented findings that challenge a long-held assumption about how Parkinson's disease and Alzheimer's pathology intersect—and they suggest the answer may depend on sex. The study examined 230 people with autopsy-confirmed Parkinson's disease, all of whom had participated in the Arizona Study of Aging and Neurodegenerative Disorders and Brain and Body Donation Program. During their lives, these participants underwent yearly clinical evaluations. After death, their brains were examined in detail for the hallmarks of Alzheimer's disease: amyloid plaques and tau tangles.
What the researchers found was striking. Women with Parkinson's disease carried a significantly heavier burden of amyloid plaques—the sticky protein clumps that accumulate in Alzheimer's brains—than men did. The numbers were concrete: women's average cortical plaque scores were 6.5 out of 15, compared to 4.9 for men. When researchers looked at neuritic plaques specifically, the pattern held: women scored 1.7 out of 3 versus 1.3 for men. More than half of the women in the study—56.8 percent—had what researchers classified as a high plaque burden. Among men, that figure was 39.7 percent. Even after accounting for age at death and APOE ε4, a major genetic risk factor for Alzheimer's disease, women remained more than twice as likely as men to have substantial amyloid accumulation.
But here is where the story takes an unexpected turn. Despite carrying more amyloid pathology in their brains, women and men with Parkinson's disease showed no meaningful differences in rates of Alzheimer's dementia or in how they performed on cognitive tests during life. Dr. Erika Driver-Dunckley, the lead author, described the puzzle directly: men and women had similar rates of Alzheimer's dementia and similar cognitive test results, yet women showed a higher amyloid plaque burden. The disconnect raised a fundamental question about how brain pathology translates—or fails to translate—into cognitive decline.
Driver-Dunckley acknowledged the tension in the findings. The greater severity of amyloid plaque pathology in women should logically affect the onset and severity of cognitive impairment, she noted, but the study did not find this effect. She suggested that a larger study might detect cognitive differences that the current sample size could not capture. It is also possible, though she did not say so explicitly, that the relationship between pathology and symptoms is more complex than researchers have assumed—that the brain's resilience, or the presence of other protective factors, might buffer some people from the cognitive consequences of amyloid accumulation.
The findings echo patterns observed in people with Alzheimer's disease alone, without Parkinson's. Previous research has shown that women with Alzheimer's disease tend to have more severe pathology and greater cognitive impairment than men. This consistency across disease contexts suggests something biological at work—a possible sex-linked susceptibility to amyloid-driven pathology that researchers do not yet understand. The mechanisms could involve hormonal differences, genetic factors, or differences in how the immune system responds to protein accumulation. None of this is yet clear.
Driver-Dunckley concluded by calling for larger studies to confirm the findings and to investigate the biological mechanisms underlying the sex differences. The next step, she said, would be to replicate the work in additional large clinicopathological studies—research that combines clinical observation with detailed examination of brain tissue after death. Understanding why women accumulate more amyloid plaques, and why that accumulation does not always translate into cognitive decline, could reshape how neurologists think about disease risk and resilience in aging.
Notable Quotes
Men and women with Parkinson's disease had similar rates of Alzheimer's dementia and similar results on cognitive testing. However, women showed a higher amyloid plaque burden compared with men.— Dr. Erika Driver-Dunckley, Mayo Clinic Arizona
The greater severity of amyloid plaque pathology in women should have an effect on the onset and severity of cognitive impairment, but our study did not find this.— Dr. Erika Driver-Dunckley
The Hearth Conversation Another angle on the story
Why does it matter that women have more amyloid plaques if their cognitive outcomes are the same as men's?
That's the central puzzle. It suggests the relationship between pathology and symptoms isn't straightforward. Either women's brains are compensating somehow, or the plaques aren't the whole story of cognitive decline.
Could it be that the study just wasn't large enough to catch the cognitive differences?
That's what the researchers suspect. With 230 people, they might be underpowered to detect smaller cognitive gaps. A larger study could reveal differences that this one missed.
What would explain why women accumulate more plaques in the first place?
That's genuinely unknown. It could be hormonal, genetic, or related to how women's immune systems handle protein accumulation. The pattern shows up in Alzheimer's disease too, so it's not unique to Parkinson's.
Does this change how doctors should treat women with Parkinson's differently?
Not yet. The findings are descriptive—they show a pattern exists. But they don't tell us what to do about it. That's why the researchers are calling for more work to understand the mechanisms.
If women have more plaques but the same cognitive outcomes, are they actually at higher risk?
That's the question. They have more pathology, which is typically a risk factor. But whether that translates into future cognitive decline, or whether some women are protected from it, remains to be seen.