Reviewed by the Help Dementia Editorial Team — our editors review every article for accuracy against guidance from the National Institute on Aging, the Alzheimer’s Association, and peer-reviewed sources.
Mixed dementia—when a person has brain changes from multiple types of dementia at the same time—typically shows lower and more scattered memory test scores compared to single-type dementia. Research from Alzheimer’s Disease Research Centers shows that over 50% of dementia patients have evidence of multiple brain pathology causes, yet their memory test scores often fall below what we’d expect from Alzheimer’s disease alone. A 72-year-old woman who showed strong cognitive decline might score 14 on the Montreal Cognitive Assessment (MoCA), which suggests moderate impairment, but the underlying cause isn’t pure Alzheimer’s—it’s a combination of Alzheimer’s changes, vascular damage, and Lewy body pathology all happening simultaneously.
This complexity is why understanding how mixed dementia affects test scores matters so much for caregivers and care partners. Memory test scores in mixed dementia cases tend to show uneven patterns across different cognitive domains. While a person with pure Alzheimer’s might show proportional decline across memory, language, and executive function, someone with mixed dementia often scores differently depending on which brain systems are most affected by which pathology. This means a single test score alone cannot tell the whole story—clinicians need to look at multiple tests together to understand what’s really happening in the brain.
Table of Contents
- How Mixed Dementia Affects Memory Test Performance
- Understanding Standard Memory Test Scores in Mixed Dementia
- Comparing Memory Test Scores Across Dementia Types
- Interpreting Memory Test Results in Mixed Dementia Cases
- Critical Limitations and False Reassurance in Memory Testing
- 2025-2026 Guidelines for Cognitive Screening in Older Adults
- Future Directions in Memory Testing and Mixed Dementia Assessment
- Conclusion
How Mixed Dementia Affects Memory Test Performance
mixed dementia creates a unique cognitive profile that doesn’t fit neatly into the typical patterns we see with single-type dementias. When autopsy studies examine brains of dementia patients, they reveal the scope of the problem: 54% of patients originally diagnosed with Alzheimer’s disease actually had coexisting pathology beyond just Alzheimer’s brain changes. This means nearly every second person we think has one type of dementia actually has multiple contributing conditions. The combination of pathologies—whether it’s Alzheimer’s plus vascular damage, or Alzheimer’s plus Lewy bodies—creates cognitive decline patterns that standard diagnostic criteria don’t always capture.
The presence of mixed pathology typically leads to lower overall cognitive scores and more rapid decline than single pathologies alone. Someone with both Alzheimer’s changes and cerebrovascular disease might score in the 10–14 range on the MoCA (which falls into the moderate impairment category of 10–17), reflecting decline that comes from two simultaneous brain processes rather than one. The clinical significance is real: mixed dementia patients often progress faster and show more behavioral complications than those with Alzheimer’s disease alone. A practical example illustrates this point: A 78-year-old man diagnosed with Alzheimer’s five years ago shows memory scores declining faster than his brother who has pure Alzheimer’s disease. Brain imaging later reveals significant small vessel vascular disease in addition to the Alzheimer’s pathology—the combination explains both the steeper decline and why his memory scores don’t fit the typical Alzheimer’s progression pattern.
Understanding Standard Memory Test Scores in Mixed Dementia
The Montreal Cognitive Assessment (MoCA) remains one of the most widely used screening tools, with normal scores ranging from 26–30, mild cognitive impairment scores between 18–25, moderate impairment (associated with Alzheimer’s) from 10–17, and severe decline below 10. However, these thresholds were established largely based on single-type dementias. In mixed dementia, a score of 16 might indicate moderate decline, but the specific pattern of errors—which questions are answered wrong and which are correct—often tells a different story than in pure Alzheimer’s. Research published in January 2025 analyzed a harmonized memory composite score across 5,287 participants across 18 Alzheimer’s Disease Centers and four research consortia, providing updated benchmarks for understanding memory test performance. The study showed that average MoCA scores differ measurably by diagnosis: people with no cognitive impairment average 27.4, those with mild cognitive impairment average 22.1 (range 19–25), and those with Alzheimer’s disease average 16.2 (range 11–21).
For mixed dementia, scores often fall at the lower end of Alzheimer’s ranges or below them, though formal diagnostic cutoffs specifically for mixed dementia are still being refined. An important limitation: These standardized scores assume that cognition declines proportionally across all domains, which is not how mixed dementia works. Someone with significant vascular damage plus early Alzheimer’s might struggle more with attention and processing speed (typical of vascular dementia) while maintaining relatively better naming and language skills. The overall MoCA score might be 14, but the pattern of deficits suggests multiple causes rather than pure Alzheimer’s disease. This is why clinicians order multiple tests rather than relying on a single number.
Comparing Memory Test Scores Across Dementia Types
When researchers compare test scores across different dementia types, striking differences emerge. The Bender-Gestalt Test, which measures visuospatial and motor abilities, shows mean scores of 3.2 in healthy controls, 7.21 in Alzheimer’s disease, and 8.04 in vascular dementia—with statistically significant differences between groups. These differences matter because they help clinicians identify which brain systems are affected. A person scoring like a vascular dementia pattern might actually have mixed dementia, where vascular damage is more prominent than Alzheimer’s changes. The MoCA’s Area Under Curve (AUC) performance—a statistical measure of how well a test distinguishes between groups—shows 0.616 for Alzheimer’s and 0.583 for vascular dementia.
These moderate AUC values mean the MoCA is reasonably good at identifying impairment but isn’t perfect, especially when multiple pathologies are present. A score in the “Alzheimer’s range” doesn’t guarantee pure Alzheimer’s disease. Mixed dementia can produce test results that look like either Alzheimer’s or vascular dementia, depending on which pathology dominates at that moment. For example, one person with mixed Alzheimer’s and vascular dementia scores 15 on the MoCA with particular difficulty on memory and drawing tasks (suggesting Alzheimer’s), while their neighbor with the same mixed diagnosis scores 13 with particular difficulty on attention and processing speed tasks (suggesting vascular dementia). The overall scores are similar, but the cognitive profiles are different, highlighting why test interpretation requires expertise beyond just comparing numbers to cutoff values.
Interpreting Memory Test Results in Mixed Dementia Cases
Test score interpretation in mixed dementia requires looking beyond the single number to understand the pattern of performance. A diagnosis of mixed dementia cannot be made from cognitive testing alone—neuroimaging, blood biomarkers, and sometimes PET imaging are needed to identify multiple pathologies. However, the cognitive test pattern can raise suspicion for mixed dementia and guide which additional tests clinicians order. Someone who scores in the Alzheimer’s range on the MoCA but shows atypical patterns on memory subtests might warrant vascular imaging to look for stroke lesions or white matter damage. The Brief Interview for Mental Status (BIMS), used in long-term care settings, scores from 0–15 with lower scores indicating memory and thinking difficulties.
While less specific than the MoCA for diagnosis, the BIMS provides a practical way to monitor cognition over time in older adults, particularly in care facilities. A person with mixed dementia showing a 6 on the BIMS (indicating moderate to severe impairment) might show improvement on that score after a stroke is treated or blood pressure is better controlled—a pattern less common in pure Alzheimer’s disease, where decline is typically relentless. One tradeoff clinicians face: Using standardized cutoff scores provides consistency and allows comparison across patients, but standardized cutoffs don’t capture the unique patterns of mixed dementia. A 68-year-old woman scores 18 on the MoCA, technically in the mild cognitive impairment range, but shows very uneven performance—excellent on memory tasks but profound difficulty with visuospatial and drawing tasks. This pattern suggests vascular damage affecting visual processing areas, not typical Alzheimer’s, which usually impairs memory first. Her overall score of 18 doesn’t capture the specificity of her cognitive profile.
Critical Limitations and False Reassurance in Memory Testing
A significant limitation of relying on memory test scores in suspected mixed dementia is that some patients show normal test scores despite having multiple brain pathologies. Cognitive reserve—the brain’s ability to compensate for damage through alternate neural pathways—means that a highly educated person with Alzheimer’s and vascular disease might score higher on standard tests than expected, potentially missing or delaying diagnosis. This false reassurance can be harmful because treatment windows for vascular disease and other reversible components of mixed dementia can be missed. Another warning involves test-retest variability. People with mixed dementia sometimes show greater variability in performance from test to test than those with single-type dementias, partly because they have multiple brain systems affected and partly because mood, sleep, or medical complications can more easily tip overall performance.
A score of 16 one month and 13 the next month might suggest rapid decline (which is medically significant) but could also reflect a urinary tract infection, medication change, or depression—all more common in people with dementia and all potentially reversible. This variability makes it harder to know whether the score change reflects true disease progression or something else. The biggest limitation of memory testing for mixed dementia diagnosis is that these tests cannot identify which pathologies are present. A MoCA score of 14 tells us there is significant cognitive impairment, but it doesn’t tell us whether the impairment comes from Alzheimer’s, vascular disease, Lewy bodies, frontotemporal dementia, or combinations of these. Only advanced imaging, biomarker testing, and sometimes autopsy can confirm the specific pathologies involved. Clinicians must treat the test score as a starting point for investigation rather than an endpoint for diagnosis.
2025-2026 Guidelines for Cognitive Screening in Older Adults
Current consensus guidelines recommend cognitive screening for seniors age 65 and older during routine checkups, with evaluations every 6–12 months for those with risk factors like hypertension, diabetes, or a family history of dementia. These updated 2026 guidelines recognize that mixed dementia is common enough that screening should be standard practice, not just for those with obvious symptoms. Early detection of cognitive decline—whether from single or mixed pathologies—opens doors to treatments that might slow progression, particularly for the vascular component of mixed dementia.
The challenge is that most primary care clinics don’t have time for full MoCA testing during routine visits. Many physicians use brief screens like the Montreal Cognitive Assessment-Blind (MoCA-B), three-word recall tests, or digital cognitive screening tools. These quick screens help identify who needs more formal testing with a neuropsychologist or cognitive specialist. For mixed dementia specifically, identifying people who score in the lower ranges on brief screens and offering them comprehensive evaluation with both cognitive testing and neuroimaging gives the best chance of understanding what’s happening in their brains.
Future Directions in Memory Testing and Mixed Dementia Assessment
The future of cognitive testing for mixed dementia involves combining traditional memory tests with blood biomarkers that can identify Alzheimer’s pathology, tau tangles, and neurodegeneration in a blood draw rather than requiring PET imaging or spinal fluid testing. Research is moving toward personalized assessment approaches that predict which specific pathologies a person has based on their cognitive pattern combined with biomarker results. This would allow for more targeted treatment strategies—addressing the vascular component with different approaches than the Alzheimer’s component, for example.
As dementia research advances, the emphasis is shifting from relying on test scores alone to understanding the biological underpinnings behind those scores. For mixed dementia patients, this shift is crucial because it allows treatment to target the multiple pathologies simultaneously rather than assuming a single diagnosis based on cognitive testing patterns. The 2025 research on harmonized memory composite scores represents progress toward this more nuanced understanding, providing better reference ranges for interpreting test results in complex cases.
Conclusion
Memory test scores in mixed dementia reflect the complexity of multiple brain pathologies occurring simultaneously, typically showing lower scores and more scattered patterns than single-type dementias. The Montreal Cognitive Assessment, Brief Interview for Mental Status, and other standard tests provide valuable information about cognitive function, but they cannot tell the full story—scores must be interpreted in context of the pattern of deficits, neuroimaging findings, and blood biomarkers. Understanding that over 50% of dementia patients have mixed pathology should prompt both clinicians and families to think beyond a single diagnosis and consider whether multiple processes might be contributing to cognitive decline.
If you or a loved one is showing signs of cognitive decline, request comprehensive evaluation including cognitive testing, neuroimaging, and biomarker assessment. Regular monitoring with memory tests every 6–12 months helps track progression and identify changes that might warrant adjustment of treatment strategies. Working with a neurologist or cognitive specialist, rather than relying on scores from a single office visit, provides the best foundation for understanding mixed dementia and planning care that addresses all the underlying conditions.
