Using a comprehensive hearing intervention designed, tested, and implemented by researchers at the University of South Florida, the multi-site ACHIEVE study examined the efficacy of hearing aids for reducing long-term cognitive decline in older adults.

Results from the largest randomized, controlled clinical trial testing the efficacy of hearing aids for reducing long-term cognitive decline in older adults were published July 18, 2023, in the journal Lancet, as well as reported for the first time at the Alzheimer’s Association International Conference® (AAIC®) 2023, held the same day, in Amsterdam, Netherlands.

Called the Aging and Cognitive Health Evaluation in Elders (ACHIEVE) study, the multisite study found that, in older adults at increased risk for cognitive decline, hearing intervention slowed down loss of thinking and memory abilities by 48% over three years.

While the results were negative in the total study population, the hearing intervention did slow cognitive decline by 48% in a study subset of older adults with mild to moderate hearing loss who are participating in an ongoing observational study of heart health. Investigators believe that the effect of the hearing intervention on reducing cognitive decline was only apparent in the group of participants from the heart health study because this group had nearly a 3-fold faster rate of cognitive decline over the study period than the healthy volunteers that enrolled in the trial. That much faster rate of decline allowed researchers to see the beneficial effects of hearing intervention on reducing this decline within the limited 3-year period of the study.

“The hearing intervention had a significant effect on reducing cognitive change within three years in the population of older adults in the study who are at increased risk for cognitive decline,” said Frank Lin, MD, PhD, of Johns Hopkins University School of Medicine and Bloomberg School of Public Health, and co-principal investigator of the ACHIEVE study. “Hearing loss is very treatable in later life, which makes it an important public health target to reduce risk of cognitive decline and dementia, along with other dementia risk factors such as less education in early life, high blood pressure, social isolation and physical inactivity.”

The overall ACHIEVE study was led by researchers at Johns Hopkins and seven additional contributing institutions. A team of researchers from USF led the hearing intervention provided in the study. From the Department of Communication Sciences and Disorders in the USF College of Behavioral and Community Sciences, Theresa H. Chisolm, PhD, professor and vice provost for Strategic Planning, Performance and Accountability, and Michelle Arnold AuD, PhD, assistant professor, collaborated with Victoria Sanchez, AuD, PhD, assistant professor in the Department of Otolaryngology in the USF Health Morsani College of Medicine.

In addition to designing the hearing intervention, the USF team also trained the study audiologists and continuously monitored the hearing intervention that was provided in the overall study.

“The ACHIEVE Study is evidence that auditory rehabilitation, including the use of hearing aids, in older adults who had more risk factors for cognitive decline slowed the rate of cognitive decline,” said USF Health’s Dr. Sanchez. “Important risk factors for cognitive decline and dementia that could be potentially addressed to help reduce dementia include hearing loss, less education in early life, smoking, diabetes, high blood pressure, social isolation, and physical inactivity. Addressing hearing loss is one way we could reduce the increase rate of older adults living with dementia.”

Established research shows that loss of hearing can increase a person’s likelihood of cognitive decline, she said, adding that further research is needed.

“Our main trial results shared today are exciting and informative, but much more research is still needed,” Dr. Sanchez said. “Our team of multi-institution investigators are continuing to follow all participants in the ACHIEVE study beyond three years to look at longer term effects of hearing intervention on cognition and other outcomes.”

This foundational work can also help guide policymakers, she said.

“Our results will hopefully create policy changes because in many parts of the world we need improved affordable access and insurance coverage for hearing treatment/intervention,” Dr. Sanchez said. “This does not mean just a hearing aid, as hearing intervention consists of two components. First are hearing aids and related hearing technologies, and second are the diagnostic and hearing care support services of an audiologist to guide the individual in using these hearing technologies to hear and communicate optimally.

“We recommend that people who have concerns about their hearing and their risk factors for cognitive decline discuss these concerns with their doctor and be seen by an audiologist to address their hearing and communication needs.”

The ACHIEVE study is a randomized trial of older adults aged 70-84 with untreated hearing loss who were free from substantial cognitive impairment, conducted at four study sites in the United States, and 977 total participants were recruited from two study populations: 238 adults participating in the Atherosclerosis Risk in Communities (ARIC) study, and 739 healthy community volunteers newly recruited to the study.

The USF Health neurobiologist focuses on understanding genetic risk factors that may offer new therapy targets to delay or protect against age-related cognitive decline

There has been a steep rise in the number of Americans dying of Alzheimer’s disease – up 145 percent between 2000 and 2017  The burden of this neurodegenerative disease, which relentlessly diminishes the mind, is not only borne by those living more years in a state of disability and dependence before dying, but by the family members who care for them.

No treatments exist to cure or slow the progression of Alzheimer’ disease, the major form of dementia afflicting an estimated 5.8 million Americans.

“The goal of our research is to reduce the (brain) pathology leading to Alzheimer’s disease, by identifying targeted treatments to delay the onset of disease and protect cognitive function,” said Gopal Thinakaran, PhD, professor of molecular medicine and associate dean for neuroscience research at the USF Health Morsani College of Medicine. “Finding ways to extend cognitive function so that an older person is still able to continue their daily activities or recognize a loved one – even for five more years – would greatly benefit both those suffering from Alzheimer’s and their families or other caregivers.”

Gopal Thinakaran, PhD (center), who holds the Bagnor Endowed Chair in Alzheimer’s Research, with his research team at the USF Health Byrd Alzheimer’s Center.

Dr. Thinakaran, an internationally recognized Alzheimer’s disease researcher, joined the University of South Florida from the University of Chicago in August to help accelerate the interdisciplinary work of the USF Health Neuroscience Institute. That includes recruiting a critical mass of basic scientists who can complement the university’s ongoing Alzheimer’s research while also expanding efforts to translate laboratory findings into new therapies for other neurodegenerative disorders, including Parkinson’s disease, ataxias, ALS, and multiple sclerosis.

Probing molecular, cellular changes underlying pathology

In addition to his leadership role, Dr. Thinakaran oversees a laboratory at the Byrd Alzheimer’s Center where he uses cutting-edge cell biology techniques and mouse models to study the molecular and cellular processes underlying Alzheimer’s disease. His research is supported by more than $6.1 million in grants from the National Institutes of Health (NIH), National Institute on Aging.

With normal brain aging, people experience minor lapses of memory (i.e., forgetting where their keys were left, or the name of someone just met) and some reduced speed in processing information. But disruptions in attention, memory, language, thinking and decision-making that interfere with daily life are signs of dementia.

In addition to overseeing his own laboratory research, Dr. Thinakaran holds Morsani College of Medicine leadership roles as associate dean of neuroscience research and Neuroscience Research Institute associate director of research.

Dr. Thinakaran’s lab pursues findings on relatively new genes identified through genome-wide association studies to gain insights into the mechanisms of late-onset Alzheimer’s disease, which affects people age 65 or older and accounts for the overwhelming majority of cases. Recently, the group has been investigating the role of bridging integrator 1 (BIN1), the second most common genetic risk factor for late-onset Alzheimer’s (exceeded only by APOE). Approximately 40% of people with Alzheimer’s have one of three variations in the BIN1 gene – a glitch in a single DNA building block (nucleotide) that heightens their risk for the disease, Dr. Thinakaran said.

Pursuing a common risk factor for late-onset Alzheimer’s

BIN1, expressed in all the body’s cells, has been shown to play a role in suppressing tumors and in muscle development — but little is known about what the protein does in the brain. Dr. Thinakaran was among the first to embrace the challenge of pursuing how BIN1 contributes to Alzheimer’s disease risk at a time when most researchers focused on amyloid and tau, two proteins considered the primary drivers of Alzheimer’s pathology.

Now, his team and a few others across the country probe what goes wrong in Alzheimer’s patients who carry the BIN1 risk allele. They have already confirmed that BIN1 is present both in the brain’s nerve cells (neurons) and its non-neuronal cells, such as oligodendrocytes and microglia.

Biochemist Melike Yuksel, PhD, a postdoctoral scholar in Dr. Thinakaran’s lab

A healthy human brain contains tens of billions of neurons that process and transmit chemical messages (neurotransmitters) across a tiny gap between neurons called a synapse. Alzheimer’s disease severely disrupts this synaptic communication, eventually killing cells throughout the brain and leading to a steep decline in memory and other signs of dementia.

“The single biggest correlation with cognitive decline is the loss of these synaptic communication centers between neurons,” Dr. Thinakaran said, adding that individuals most susceptible to developing full-blown Alzheimer’s in later life are those who lose the most synapses.

In a study published March 10 in Cell Reports, Dr. Thinakaran and colleagues demonstrated for the first time that the loss of BIN1 expression impaired spatial learning and memory associated with remembering where things are located. The researchers used an Alzheimer’s disease “knockout” mouse model in which neuronal BIN1 expression was inactivated in the hippocampus, a brain region involved with higher cognitive functions.

Discovering a defect in brain cell communication

A lack of BIN1 leads to a defect in the transmission of neurotransmitters needed to activate the brain cell communication that allows us to think and behave, the researchers found. Further analysis found that BIN1 was primarily located in neurons that send neurotransmitters across the synapse (presynaptic sites) rather than residing on those neurons that receive the neurotransmitter messages (postsynaptic sites). The BIN1 deficiency was also associated with reduced synapse density; a back-up of docked vesicles, the tiny bubble-like carriers that transfer neurotransmitters from presynaptic to postsynaptic neurons; and likely slower release of the neurotransmitters from their vesicles.

“Our findings so far that BIN1 localizes right at the point of (presynaptic) communication and may be precisely regulating neurotransmitter vesicle release brings us much closer to understanding how BIN1 could exert its function as a risk factor (for Alzheimer’s disease),” Dr. Thinakaran said. “We suspect it helps control how efficiently neurons communicate.”

Peering into the brain, one synapse at a time. Electron micrograph depicting selected region of a mouse brain hippocampus, the brain area responsible for learning and memory. A single synapse is marked with the yellow outline.  The human brain is estimated to have trillions of these synapses, which transmit information from one neuron to the next.| Image courtesy of Gopal Thinakaran, PhD

Antibody-stained mouse brain with Alzheimer’s disease β-amyloid deposits. The amyloid precursor proteins within healthy nerve cells and swollen neuronal processes are depicted in blue. The late-onset Alzheimer’s risk factor BIN1 is shown in green, and a marker for brain glial cells responsible for neuroinflammation is shown in magenta.| Image courtesy of Gopal Thinakaran, PhD

Dr. Thinakaran’s team also became interested in investigating whether BIN1 risk variants can interfere with the protective capacity of glia (cells supporting neurons) to mount a full inflammatory response needed to clear toxins from the brain. His USF Health group will work with researchers at Emory University to further investigate why the absence of BIN1 may impair the brain’s removal of abnormal beta-amyloid protein associated with Alzheimer’s disease.

Exploring the type 2 diabetes connection

Collaborating with a coprincipal investigator at the University of Kentucky, Dr. Thinakaran also explores the molecular link between type 2 diabetes and Alzheimer’s disease progression. An Alzheimer’s mouse model created by the Thinakaran lab allows researchers to turn on, or switch off, production of the human hormone amylin in the pancreas.

Amylin is secreted by the pancreas at higher levels, along with insulin, as diabetes begins to develop. Small amounts of this excess amylin migrate from pancreatic cells into the bloodstream and can cross the blood-brain barrier, especially in older brains where the protective barrier becomes leakier. The amylin then mixes with the brain’s beta-amyloid, which eventually builds into the sticky amyloid plaques that are a hallmark of Alzheimer’s pathology. The researchers will test in their preclinical model whether this brain amylin elevates the risk for Alzheimer’s disease, and if reducing amylin in peripheral circulation can help prevent or slow damage to cognition.

Dr. Thinakaran with biological scientist Stanislau (Stas) Smirnou

Scientists are still trying to figure out why some people remain cognitively resilient throughout life despite having neuropathology that would otherwise cause dementia. On the horizon, Dr. Thinakaran said, integrating large databases of gene expression and individual cell types will help scientists drill deeper into what specific inflammatory, metabolic and neural circuit changes shift a normally aging brain to one in which the abilities to remember, think and reason abnormally accelerate.

At the same time, data on genetics and environment/lifestyle (including diet, physical and mental exercises, sleep patterns and uncontrolled cardiovascular risk factors such as hypertension, diabetes and high cholesterol) are being collected both for patients in various stages of Alzheimer’s disease and for older adults with healthy cognitive function. “Bridging these two sets of data will be extremely valuable in understanding what confers higher risk and delineating what can keep our brains healthy as we age,” Dr. Thinakaran said.

Fascinated by a field with unprecedented challenges

Dr. Thinakaran holds a PhD in molecular biology and genetics from the University of Guelph in Canada. He completed a postdoctoral research fellowship in neuropathology and was an assistant professor of pathology at Johns Hopkins University School of Medicine. Before joining USF Health, he was a professor of neurobiology at the University of Chicago, where he built one of the country’s leading laboratories investigating pathways responsible for Alzheimer’s disease pathology and neuronal dysfunction.

Known as an accomplished scientist and thought leader who does not hesitate to tackle uncharted territory, Dr. Thinakaran studied muscle differentiation as a PhD student. But, he soon realized that muscle research had advanced to a stage where it was unlikely he could make much of an impact. At that time (early 1990s) Alzheimer’s disease research was just gaining momentum in molecular and cellular biology and posing unprecedented challenges, he said.

Biological scientist Xiaolin Zhang, MS

Once Dr. Thinakaran’s interest in Alzheimer’s was sparked during his postdoctoral training at Johns Hopkins, he seized the opportunity to pursue the emerging area of neuroscience research. “In many ways the brain and its complexity as we age is the final frontier in understanding human behavior. We’re continuing to learn every day the basics of how this organ system works, and what goes wrong when it doesn’t,” he said. “It’s a field that still has great opportunities for the next generation of young minds to make a difference.”

Dr. Thinakaran has authored more than 140 peer-reviewed publications. He is associate editor for the journals Molecular Neurodegeneration and Genes and Diseases and an editorial board member for Neurodegenerative Diseases and for Current Alzheimer Research. He serves on several scientific review/advisory committees for federal, private and public institutions. Dr. Thinakaran has received numerous awards, including the Alzheimer’s Association prestigious Zenith Fellows Award supporting senior scientists pursuing new ideas to advance Alzheimer’s and dementia research.

Some things you may not know about Dr. Thinakaran

• Dr. Thinakaran combines his artistic talents of drawing and painting with his research. Andy Warhol-like microscopic art he created won a competition and was featured as the program cover for a brain research symposium at the University of Chicago. The multicolor montage of images depicts a mouse brain section (hippocampus) stained to visualize β-secretase, an enzyme critical for generating the hallmark Alzheimer’s disease β-amyloid pathology.
• He is married to neurophysiologist Angèle Parent, PhD, associate professor of molecular medicine at the Byrd Alzheimer’s Center. They have three children: Abigaël, a freshman and aspiring neuroscientist at the University of Chicago; Daphné, 14; and Cédric, 12.
• Dr. Thinakaran enjoys cooking authentic South Indian food and other international dishes with his family.

This microscopic brain art created by Dr. Thinakaran was featured on the program cover of a University of Chicago brain research symposium.

-Video by Allison Long, and photos by Freddie Coleman, USF Health Communications and Marketing

His team searches beyond the hallmark Alzheimer’s disease proteins for alternative treatments

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In his laboratory at the USF Health Byrd Alzheimer’s Center, neuroscientist David Kang, PhD, focuses on how different types of proteins damage the brain when they accumulate there. In the case of Alzheimer’s disease, decades of good science has zeroed in on amyloid and tau, as the two types of hallmark proteins driving the disease process that ultimately kills brain cells.

Dr. Kang and his team investigate molecular pathways leading to the formation large, sticky amyloid plaques between brain cells, and to the tau neurofibrillary tangles inside brain cells –including the interplay between the two proteins. But, he is quick to point out that amyloid and tau are “not the full story” in the quest to understand how normally aging brains go bad.

“Our goal is to understand as much of the entire Alzheimer’s disease process as possible and then target specific molecules that are either overactive or underactive, which is part of the drug discovery program we’re working on,” said Dr. Kang, professor of molecular medicine and director of basic research for the Byrd Alzheimer’s Center, which anchors the USF Health Neuroscience Institute.

Neuroscientist David Kang, PhD, (third from left)  stands with his team in his laboratory at the Byrd Alzheimer’s Center, which anchors the USF Health Neuroscience Institute.

Attacking dementia from different angles 

Dr. Kang’s group takes a multifaceted approach to studying the biological brain changes that impair thinking and memory in people with Alzheimer’s, the most common type of dementia, as well as Lewy body, vascular and frontotemporal dementias.

That includes examining how damaged mitochondria, the energy-producing power plants of the cell, contribute to pathology in all neurodegenerative diseases. “Sick mitochondria leak a lot of toxins that do widespread damage to neurons and other cells,” Dr. Kang said.

Dr. Kang’s team was the first to identify how mutations of a gene, called CHCHD10, which contributes to both frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), cause both mitochondrial dysfunction and protein pathology called TDP-43. Their findings on the newly identified mitochondrial link to both neurodegenerative diseases were published in Nature Communications in 2017.

The role of selective degradation in ridding cells of abnormal proteins, old or damaged organelles (including mitochondria) and other debris is another key line of research pursued by Dr. Kang and colleagues.

A single stained nerve cell | Microscopic image courtesy of Kang lab

“We believe something more fundamental is going wrong in the brain during the aging process to tip the balance toward Alzheimer’s disease – beyond what we call proteinopathy” or deposits of malformed proteins like toxic amyloid and tau, said Dr. Kang, whose work is bolstered by nearly $8 million in grant funding from the National Institutes of Health (NIH), the Veterans Administration (VA merit awards) and the Florida Department of Health.

“I think one of the fundamental things happening is that the (cellular) plumbing system isn’t working to clear out all the accumulating junk,” he said. “That’s why we’re looking at the protective clearance mechanisms (autophagy and mitophagy) that would normally quickly remove misfolded proteins and dysfunctional mitochondria.”

Unfortunately, pharmaceutical trials to date have yielded no effective treatments for Alzheimer’s disease, the sixth leading cause of death in the U.S.  Most clinical studies have centered on developing medications to block or destroy the amyloid protein plaque formation, and a few have targeted the tau-containing neurofibrillary tangles. The five Alzheimer’s drugs currently available may provide temporary relief of symptoms, such as memory loss and confusion. But, they do not prevent or delay the mind-robbing disease as toxic proteins continue to build up and dismantle the brain’s communication network.

Lesson learned: The critical importance of intervening earlier

Some scientists argue that the “amyloid hypothesis” approach is not working. Dr. Kang is among those who maintain that amyloid plays a key role in initiating the disease process that leads to brain atrophy in Alzheimer’s – but that amyloid accumulation happens very early, as much as 10 to 20 years before people experience memory problems or other signs of dementia.

Early detection and treatment are key, Dr. Kang says, because as protein plaques and other lesions continue to accumulate in the brain, reversing the damage may not be possible.

“One reason we’ve been disappointed in the clinical trials is because so far they have primarily targeted patients who are already symptomatic,” Dr. Kang said. “Over the last decade we’ve learned that by the time someone is diagnosed with early Alzheimer’s disease, or even mild cognitive impairment, the brain has degenerated a lot. And once those nerve cells are gone they do not, for the most part, regenerate… The amyloid cascade has run its course.”

As protein plaques and other lesions continue to accumulate, becoming apparent with MRI imaging, reversing the damage may not be possible.  So, for anti-amyloid therapies – or even those targeting downstream tau – to work, patients at risk of Alzheimer’s need to be identified and treated very early, Dr. Kang said.

USF Health is recruiting healthy older adults with no signs of memory problems for a few prevention trials. A pair of Generation Program studies will test the effectiveness of investigational anti-Alzheimer’s drugs on those at high genetic risk for the disease before symptoms start. And, the NIH-sponsored Preventing Alzheimer’s with Cognitive Training (PACT) study is examining whether a specific type of computerized brain training can reduce the risk of mild cognitive impairment and dementias like Alzheimer’s disease in those age 65 and older.

To accelerate early intervention initiatives, more definitive tests are needed to pinpoint biomarkers that will predict Alzheimer’s disease development in genetically susceptible people. Dr. Kang is hopeful about the prospects.  His own team investigates how exosomes, in particular the lipid vesicles that shuttle proteins and other molecules from the brain into the circulating bloodstream, might be isolated and used to detect people at risk of proteinopathy.

“I think within the next five years, some type of diagnostic blood test will be available that can accurately identify people with early Alzheimer’s brain pathology, but not yet experiencing symptoms,” he said.

Graduate research assistant Yan Yan, a member of Dr. Kang’s research team, works at a cell culture hood.

Searching for alternative treatment targets

Meanwhile, Dr. Kang’s laboratory continues searching for other treatment targets in addition to amyloid and tau — including the enzyme SSH1, which regulates the internal infrastructure of nerve cells, called the actin cytoskeleton. SSHI, also known as slingshot, is needed for amyloid activation of cofilin, a protein identified by the USF Health neuroscientists in a recent study published in Communications Biology as a possible early culprit in the tauopathy process.

“Cofilin is overactive in the brains of Alzheimer’s patients so if we can inhibit cofilin by targeting slingshot, it may lead to a promising treatment,” Dr. Kang said.

Ultimately, as with other complex chronic diseases, Alzheimer’s may not be eliminated by a single silver-bullet cure.  Rather, Dr. Kang said, a combination of approaches will likely be needed to successfully combat the neurodegenerative disorder, which afflicts 5.8 million Americans.

“I think prevention through healthy living is definitely key, because brain aging is modifiable based on things like your diet as well as physical activity and brain exercises,” he said.  “Also, we need to focus on earlier diagnosis, before people become symptomatic, and develop next-generation drugs that can attack the disease on multiple fronts.”

Xingyu Zhao, PhD, a research associate in the Department of Molecular Medicine, is among the scientists in Dr. Kang’s laboratory studying the basic biology of the aging brain.

Fascinated by how the brain works — and malfunctions

Dr. Kang came to USF Health in 2012 after nearly 20 years as a brain researcher at the University of California San Diego, where he earned M.S. and PhD degrees in neurosciences and completed NIH National Research Service Award fellowships in the neuroplasticity of aging.

As an undergraduate Dr. Kang switched from studying engineering to a dual major in science/psychology. He began focusing on neurosciences in graduate school, he said, because tackling how the brain works and malfunctions was fascinating and always challenged him.

“With every small step forward, we learn something else about the basic biology of the aging brain,” said Dr. Kang, “It’s not just helpful in discovering what therapeutic approaches may work best against Alzheimer’s disease – we’re also learning more about other neurodegenerative conditions affecting the brain.”

In addition to leading day-to-day research operations at the Byrd Center and helping to recruit new Alzheimer’s investigators, Dr. Kang holds the Mary and Louis Fleming Endowed Chair in Alzheimer’s Research and serves as a research neurobiologist at the James A. Haley Veterans Haley Veterans’ Hospital.

He has authored more than 50 peer-reviewed journal articles on brain aging and Alzheimer’s disease research. A member of the NIH Clinical Neuroscience and Neurodegeneration Study Section since 2016, he has served on multiple national and international editorial boards, scientific panels and advisory boards.

Dr. Kang sits next to a computer monitor depicting stained microscopic images — a single neuron (far left) and the two hallmark pathological proteins for Alzheimer’s disease, tau tangles (center) and amyloid plaques (right).

Some things you may not know about Dr. Kang

• His parents were Presbyterian missionaries in Africa, so he spent nine years of his early life (third through 10^th grade) in Nigeria.
• Dr. Kang practices intermittent fasting, often forgoing breakfast and eating only within an 8-hour window. Animal studies indicate the practice may contribute to lifespan and brain health by improving cellular repair through the process of autophagy, he said. “Autophagy really kicks your cells’ plumbing system into gear to clear out all the waste.”

-Video and photos by Allison Long, USF Health Communications and Marketing