If a parent or grandparent frequently forgets names, misplaces items, or retells the same stories, many people would immediately consider a diagnosis of Alzheimer’s disease. For decades, Alzheimer’s has dominated public perception of dementia, serving as a catch-all term for memory loss.
However, this assumption is increasingly being challenged. Neurologists have discovered that a significant number of individuals exhibiting Alzheimer’s-like symptoms actually suffer from a different condition, which many families and even healthcare professionals are only beginning to understand.
This condition is known as LATE, short for limbic-predominant age-related TDP-43 encephalopathy. Research indicates that LATE is responsible for approximately 15-20% of all dementia cases, disproportionately affecting 1 in 3 individuals over the age of 85.
LATE was formally defined in 2019, and clinical guidelines clarifying its diagnosis were published just last year.
Dr. Andrew Budson, Chief of Cognitive Behavioral Neurology at the Boston Veterans Affairs Healthcare System and Professor of Neurology at Boston University, states, “I didn’t know how common it was until I started testing people for biomarkers.”
He adds, “It became evident that many individuals we previously thought had Alzheimer’s actually did not, despite exhibiting nearly identical clinical symptoms.”
As understanding of these distinctions evolves, so too does the meaning behind a dementia diagnosis. If your elderly relative’s memory loss is attributed to LATE instead of Alzheimer’s disease, it may progress more gradually and remain more focused.
Symptoms of LATE
LATE is primarily characterized by gradual memory loss, particularly regarding recent events—often referred to as episodic memory. Patients may experience difficulties remembering conversations, appointments, or even television shows viewed the previous night.
As LATE advances, speech may also be impacted. Some individuals struggle to find words, while others may forget the meanings of familiar terms. Dr. Budson recalls a patient who could no longer grasp the meaning of the word “Charade” and later became confused about what a pumpkin was. “It’s as though they grew up in a world without pumpkins,” he notes.
Over time, subtle behavioral changes may arise. “When the lower frontal lobes are affected, behavioral issues can surface,” explains Budson. “It’s not severe, but individuals may lose their inhibitions, leading to socially inappropriate comments about others’ appearance.”
A key difference between LATE and Alzheimer’s is the disease’s tempo. LATE generally presents later in life, typically in the late 70s or 80s, and progresses more slowly, allowing individuals to experience isolated memory loss for many years before cognitive abilities decline significantly.
Dr. David Wolk, a professor of neurology at the University of Pennsylvania, states, “In LATE, the slow and progressive memory loss can persist for years even in the absence of other significant symptoms.” This gradual trajectory can greatly improve a family’s quality of life and long-term planning.
Complicating matters is the fact that LATE often coexists with Alzheimer’s disease. Up to half of LATE patients may exhibit Alzheimer-type pathology in their brains, which can exacerbate decline when both conditions are present, according to Dr. Wolk.
Differentiating Between Late-Life Dementia, Alzheimer’s Disease, and Normal Aging
Distinguishing early dementia from normal age-related forgetfulness is challenging. Many healthy older adults find themselves slower at recalling names, needing reminders, or struggling to multitask.
The critical difference lies in the memory mechanism. In normal aging, difficulties usually stem from retrieving stored information, as Prompts can often help refresh a person’s memory.
Conversely, in the advanced stages of Alzheimer’s disease, the memory trace itself may be irretrievably lost. Budson likens memory to a filing system: the frontal lobe acts as a clerk, gathering information and directing it to appropriate storage within the hippocampus, the cabinet that houses this data.
In normal aging, office inefficiencies arise; repetition becomes necessary, retrieval slows, but information, when entered, remains accessible. Alzheimer’s disease and LATE, however, damage the filing cabinet itself, leading to lost information despite skilled clerks.
Alzheimer’s disease spreads rapidly, affecting multiple brain networks, including memory, planning, problem-solving, spatial awareness, and language. In contrast, LATE tends to concentrate its impact on memory, progressing at a slower pace overall.
Pathologically, Alzheimer’s disease is marked by amyloid-beta plaques and tau tangles, while LATE is driven by TDP-43 aggregates. This distinction becomes vital as new treatments target specific biological pathways.
Understanding the Basis of LATE
At its core, LATE is caused by a malfunctioning protein. In healthy neurons, proteins maintain structure and function. In LATE, TDP-43 protein aggregates within neurons, leading to cell damage and death.
This protein was first linked to ALS and a type of frontotemporal dementia around 20 years ago. Researchers found that TDP-43 often appears in older brains, triggering a specific memory loss pattern that justifies its own diagnosis.
Three primary brain structures are significantly affected by LATE, explains Budson: the hippocampus, the lateral temporal lobe, and the lower frontal lobe. Each area is crucial for cognition, affecting memory formation, language comprehension, and impulse control.
Can Doctors Diagnose LATE?
For a long time, LATE could only be diagnosed post-mortem through direct examination of brain tissue, which still serves as the gold standard. However, clinicians are increasingly utilizing cognitive tests and biomarker evidence to suspect LATE during a patient’s lifetime.
Dr. Budson explains, “If a biomarker test for Alzheimer’s comes back negative, I infer, ‘This is likely LATE.’ Therefore, in individuals demonstrating Alzheimer-like memory issues but lacking amyloid or tau—key Alzheimer’s indicators—LATE emerges as a viable possibility.
One pressing question for patients and families is whether a LATE diagnosis changes treatment options. The answer is complex; new Alzheimer’s treatments target amyloid pathways and are less effective for LATE patients. However, older Alzheimer’s medications that enhance acetylcholine—a neurotransmitter involved in memory—may still offer benefits. Dr. Wolk acknowledges, “There’s evidence that acetylcholine declines in late life, too.”
Dr. Budson encourages not to abandon treatment prematurely, asserting, “I’m confident that many LATE patients were included in clinical trials leading to these drugs’ approval.” He reassures, “Patients and doctors should continue treatment even if Alzheimer’s isn’t the diagnosis, as it will likely benefit LATE patients as well.”
Currently, no treatments specifically target TDP-43 in LATE, though one clinical trial is underway. Dr. Wolk notes that insights from ALS and frontotemporal dementia could be instrumental in future applications.
You may think that differentiating between dementia types is insignificant due to limited treatments and similar outcomes; however, accurate diagnosis is crucial. Understanding that LATE progresses slowly allows families to plan care, preserve independence, and set realistic expectations.
From a scientific standpoint, precise diagnosis is essential for conducting clinical trials effectively and understanding treatment impacts. As the population ages, conditions primarily affecting the elderly—like LATE—will become more prevalent.
Dr. Wolk emphasizes, “LATE is highly common and progresses slowly, providing insight into age-related cognitive decline before it transcends normal aging.” As society ages, addressing this condition will pose a growing public health concern.
While LATE may not receive the same level of publicity as Alzheimer’s disease, many families are already grappling with its implications.
Dr. Budson provides a realistic perspective: “LATE typically advances slowly and affects individuals later in life; many don’t become severely ill before passing from other causes. While that may not be comforting, it is realistic.” What LATE reveals is the complexity hidden beneath the term dementia: similar symptoms can arise from different biological mechanisms, leading to varied decline rates, risks, and treatment responses.
The distinction may not change daily care for patients and families, but as diagnostic tools improve, they increasingly influence clinicians’ predictions about future developments, how research trials are structured, and the direction of emerging treatments.
Source: www.sciencefocus.com
