Remember Me? A Guide to Alzheimer's Disease and Hearing Loss

Jess Dancer, Ed.D., Professor Emeritus of Audiology, University of Arkansas at Little Rock

Phyllis Watkins, Executive Director, Alzheimer's Arkansas Programs and Services

Oscar-winning actor Charlton Heston said yesterday that he is suffering from what appears to be Alzheimer's disease, a slow-progressing and fatal brain disorder that gradually robs the victim of the ability to remember and think.

"For now I'm not changing anything," said Mr. Heston, 77, in a taped statement played for the press at the Beverly Hills Hotel, not far from his home. "I'll insist on work when I can; the doctors will insist on rest when I must. If you see a little less spring in my step, if your name fails to leap to my lips, you'll know why. And if I tell you a funny story for the second time, please laugh anyway."

-Washington Times, Saturday, August 10, 2002

Introduction:

With the above statement, Charlton Heston, who played Moses in the Ten Commandments, joined over 4 million Americans with Alzheimer's disease taking that long journey of goodbye into what Ronald Reagan called "the sunset of my life," and what his wife Nancy described as "distant place where I can no longer reach him."

The story of Alzheimer's disease began in l906 when Dr. Alois Alzheimer, a physician in Germany for whom the disease is named, studied the brain of a 51-year-old woman with symptoms of depression, hallucinations, and dementia. He discovered ... "a paucity of cells in the cerebral cortex ... and clumps of filaments between the nerve cells."¹ Dr. Alzheimer's finding of plaques and tangles within the tissues of the brain remains the classic hallmarks of the disease even today, with the definitive diagnosis of Alzheimer's confirmed only at autopsy. Perhaps the most poignant moment in this discovery was when the patient uttered: "I have lost myself."

Alzheimer's disease is marked by the loss of cognitive ability, generally over a period of 10-15 years, and associated with the accumulation of beta amyloid plaques and neurofibrillary tangles throughout the brain. These abnormal tissues prevent the proper transmission of electrochemical signals necessary for information processing and retrieval and suffocate neurons by inhibiting blood supply. The disease is characterized by impairment in memory and a disturbance in at least one other thinking function, such as language or perception of reality.

Alzheimer's disease is one of a number of dementias, defined generally as a deterioration of intellectual faculties, such as memory, concentration, and judgment, resulting from an organic disease or a disorder of the brain. These conditions may also produce emotional disturbances and personality changes. The word dementia has Latin roots meaning "madness" or "senseless." Dementia may be caused by many medical conditions, some reversible and some progressive, which can result in cerebral dysfunction. Of the many causes of dementia, Alzheimer's disease is responsible for the majority of cases.

Alzheimer's Disease Overview:

4.5 million Americans have Alzheimer's disease, which is double the numbers reported in l980 ⁹. By mid-century, the total may rise to as many as 16 million unless a cure is found. A Gallup poll found that 1 in 10 Americans said they had a family member with Alzheimer's disease and 1 in 3 knew someone with the disease. Increasing age is the greatest risk actor for Alzheimer's disease, with 1 in 10 adults over age 65 affected by the disorder and nearly half over age 85 affected. National direct and indirect annual costs for individuals with Alzheimer's disease are at least $100 billion. More than 7 out of 10 people with Alzheimer's disease live at home, where family and friends provide almost 75% of care. Half of all nursing home residents have Alzheimer's disease or a related disorder. Alzheimer's disease is the 4th leading cause of death in adults over the age of 65, after heart disease, cancer, and stroke.

Dementia/Alzheimer's Disease and Hearing Loss?

Almost 20 years ago, Weinstein and Amsel ² studied the prevalence of hearing loss in 30 institutionalized patients with the diagnosis of senile dementia and found that 83% of the sample had hearing loss that exceeded 25 dB HL, a percentage significantly higher than a comparable random sample of patients without dementia. Interestingly, 10 of the subjects, or 33%, were reclassified to a less severe category of dementia when their scores on the Mental Status Questionnaire improved through the use of an auditory trainer for amplification.

Researchers at the University of Washington's Department of Medicine conducted a study of hearing loss in 100 cases with Alzheimer's disease ³ compared to matched controls. The prevalence of hearing loss of 30 dB HL or more was significantly higher in the Alzheimer's group, and the degree of hearing loss correlated with the severity of cognitive decline as measured by the Mini-Mental State Examination. Results lend support to the hypothesis that hearing impairment contributes to cognitive dysfunction in older adults.

The relationship of hearing impairment to dementia and cognitive dysfunction was further studied in 52 consecutive patients in a memory disorders clinic by researchers at the University of South Florida ⁴. Most patients met the criteria for Alzheimer's disease, and 49 of the 52, or 94%, failed the puretone screening. The researchers concluded that a hearing evaluation should be a part of any assessment of cognitive function.

In addition to peripheral hearing loss, researchers at Vanderbilt University studied central auditory function in patients in the early to middle stages of Alzheimer's disease through administration of five central tests including the synthetic sentence identification with ipsilateral competing message (SSI-ICM), dichotic digits, dichotic sentence identification (DSI), pitch patterns, and duration patterns ⁵. The Alzheimer's patients scored lower than the matched control group on four of the five measures used, and the researchers suggested screening for central auditory dysfunction, since impaired processing could influence the assessment of any cognitive deficit as well as audiologic management.

In another study of central auditory processing in Alzheimer's disease, researchers at the University of Washington School of Medicine documented the prognostic significance of a central auditory speech-processing deficit for the subsequent onset of probable Alzheimer's disease ⁶. These researchers studied initially dementia-free volunteers from the Framingham Heart cohort and identified 40 subjects who had received a diagnosis of probable Alzheimer's over an average of 8.4 years of follow-up.

Seven of the 15 subjects with a score of 50% or less correct on the synthetic sentence identification with ipsilateral competing message (SSI-ICM), or 47.7%, developed Alzheimer's disease during the follow-up period. The researchers concluded that central auditory speech-processing deficits may be an early manifestation of probable Alzheimer's disease and may precede the onset of dementia diagnosis by many years.

The Brain & Alzheimer's Disease:

In Alzheimer's disease, there is abnormal atrophy of the brain as compared to the normal brain. The grooves and furrows of the brain are widened while the gyri shrink and the fluid-contained ventricles enlarge. Short-term memory and the ability to perform routine tasks are affected early in the process when brain cells in the hippocampus and basal forebrain begin to degenerate. As the disease spreads throughout the cerebral cortex, judgment declines, emotional outbursts may occur, and language is impaired until communication is completely lost. In the final stages, the patient is bedridden and totally dependent upon others.

The Auditory System & Alzheimer's Disease:

Researchers at the University of Southern California School of Medicine in the department of Otolaryngology-Head and Neck Surgery studied the temporal bones from eight patients with Alzheimer's disease and compared them with eight controls ⁷. Surprisingly, they found an absence of neurofibrillary tangles and neuritic plaques in the cochlear and spiral ganglion tissues and suggest that the peripheral auditory system, unlike the peripheral visual and olfactory systems, may not be directly affected by Alzheimer's disease. However, the negative consequences of age-related peripheral hearing loss in older adults, including depression and cognitive decline, may increase the overall severity of an Alzheimer's diagnosis unless the peripheral loss is recognized and treated as an independent but co-existing factor.

In contrast, researchers at the Mercer's Institute for Research on Ageing at St. James's Hospital in Dublin, Ireland reported patients with Alzheimer's disease do have pathologic involvement of the primary auditory pathway, including the inferior colliculus, medial geniculate body, primary auditory cortex and secondary auditory cortex, along with dysfunction of the reticular activating system ⁸. Such findings indicate both impairment of central auditory function and arousal as features of Alzheimer's disease.

Risk Factors for Alzheimer's Disease:

There are a number of risk factors ¹⁰ for developing Alzheimer's disease, with age being the most important one. The number of affected people doubles every five years beyond age 65. Family history is another risk factor, with a 1.5 times great risk of developing Alzheimer's if one parent has the disease and a 5 times greater risk if both parents are affected.

Familial Alzheimer's, which affects less than 10% of patients, starts earlier in life, generally before age 50. There is a strong genetic component in familial Alzheimer's, with mutations in genes 21, 14, and 1 associated with a predisposition to the condition.

The majority of Alzheimer's cases are late-onset, developing after age 65, with no known cause and no obvious inheritance pattern. An increased risk of developing late-onset disease is related to one of three apolipoprotein (apoE) genes found on chromosome 19. The apoE genes code for a protein that helps carry cholesterol in the bloodstream, and the presence of apoE4 places a person at greater risk.

Other risk factors that have been studied over the years that show a consistent relationship to the development of Alzheimer's disease are as follows:

• Gender - women are somewhat more likely to develop Alzheimer's disease than men.
  
  
• Ethnicity -The rates among African-Americans and Latinos are higher than caucasians while rates for Asians and Native Americans are lower.
  
  
• Intellectual Ability - higher educational levels seem to reduce the risk of Alzheimer's disease.
  
  
• Head injury - increased risk for those with a history of moderate or severe head injury with loss of consciousness.
  
  
• Depression - depressive symptoms correlate strongly with the development of Alzheimer's disease within a year.
  
  
• Marital status - higher risk in those who have never married.
  
  
• Diet - higher risk in those with greater intake of saturated and transfats.
  
  
• Hobbies/leisure activities - lower risk in those who participate regularly in mental, social, or productive activities such as reading, play cards or board games, doing crossword puzzles, and visiting museums.
  
  
• Down's Syndrome - higher risk of developing Alzheimer's by middle age, possibly due to mutations in chromosome 21.
  
  
• High cholesterol/hypertension in midlife - higher risk in later life.

Warning Signs of Alzheimer's Disease:

..."I get so tired of mother asking me over and over again where her dentures are. She misplaces them all the time and then accuses me of stealing them! If she isn't asking about her dentures, she is telling me the same story about her childhood, over and over again, word for word. She won't help me with cooking anymore, saying she can't read or remember the recipes she taught me in the first place. She won't pay any of her bills and she throws them all away if I don't get them out of the mailbox first. Worst of all, she refuses to take a bath or change her clothes, saying that a stranger is in the bathroom who spies on her during the day. She won't go to bed at night because she sees 'goobers' under the sheets and she gets irate if I tell her there's nothing there. She used to be full of energy and kindness. Now she mopes around with a mean expression on her face. Yesterday she wandered out into the back yard and began screaming that she wanted to go home. Is she going crazy, or am I?"

The above story is fictional but all-to-familiar to family members caring for patients with Alzheimer's disease. The 10 warning signs ¹¹ of Alzheimer's disease, which are variable and do not affect all patients to the same degree, include the following:

• MEMORY LOSS, especially for recent events
  
  
• DIFFICULTY PERFORMING FAMILIAR TASKS, such as cooking a meal
  
  
• LANGUAGE PROBLEMS, such as forgetting a familiar word
  
  
• DISORIENTATION IN TIME AND PLACE, such as forgetting an appointment or where the doctor's office is located
  
  
• POOR OR DECREASED JUDGMENT, such as buying unneeded products
  
  
• PROBLEMS WITH ABSTRACT THINKING, such as understanding a humorous remark or solving math problems
  
  
• MISPLACING THINGS, such as dentures or hearing aids
  
  
• CHANGES IN MOOD OR BEHAVIOR, such as sudden bursts of anger or agitation for no apparent reason
  
  
• CHANGES IN PERSONALITY, usually for the worse
  
  
• LOSS OF INITIATIVE, with little or no interest in former activities or hobbies

Most adults occasionally experience one or more of these symptoms in their everyday lives, such as misplacing their keys, forgetting where they parked their car, or not remembering an old friend's name. In contrast, the person with Alzheimer's disease forgets they have keys or a car and may not recognize an old friend at all.

Diagnosis:

No single test can detect Alzheimer's disease. The diagnosis is one of exclusion by ruling out other causes. The Mayo Clinic uses the following diagnostic routine ¹²:

• Complete physical exam
  
• Detailed medical history
  
• Neuropsychological assessment
  
• Psychiatric assessment
  
• Blood tests
  
• Brain imaging
  
• Electroencephalography and electromyography, along with urine and cerebrospinal fluid analysis

A diagnosis of "probable" Alzheimer's is made on the basis of the following criteria ¹³:

• Dementia is present.
  
• The history, physical, and mental status are consistent with Alzheimer's disease.
  
• Blood tests and review of medications do not reveal any cause of cognitive impairment.
  
• Brain imaging studies are normal or show atrophy of brain tissues.

A definitive diagnosis of Alzheimer's disease can only be made at autopsy through the verification of plaques and tangles with the brain and brainstem.

Testing Patients with Alzheimer's Disease for Hearing Loss:

In the early stages of Alzheimer's disease, traditional behavioral tests of hearing such as puretone and speech audiometry are generally successful, although modifications may be necessary for test validity and reliability. Modifications may include simplifying instructions, having the patient say "yes" rather than raising a finger or pressing a button, reminding the patient to respond throughout the testing situation, presenting pulsed tones rather than continuous ones, and slowing down the presentation of speech stimuli. Allowing the caregiver to accompany the patient into the booth can help to keep the patient calm and on-task during testing, and your warmth and friendliness with the patient can also have a positive effect on test outcomes.

In the later stages of the disease, behavioral tests may no longer work, and more objective tests such as Otoacoustic Emissions ¹⁴ or the Auditory Steady State Response ¹⁵ may be necessary to obtain estimated thresholds.

Stages of Alzheimer's Disease:

The cognitive, affective, and physical changes associated with Alzheimer's disease can be broken down into three broad stages ¹⁶: Early Stage of 2-4 years (mild cognitive decline), Middle Stage of 2-12 years (moderate cognitive decline and decline in functioning of many body systems), and Late Stage of 1-3 years (severe cognitive decline and complete deterioration of the personality).

The diagnosis of Alzheimer's disease is usually made in the longer middle stage, where symptoms worsen to the point they can no longer be ignored by friends and family.

Alzheimer's Disease Treatment:

There is no cure for Alzheimer's disease, but five medications are currently available to slow the symptoms and improve cognitive functioning ¹⁷:

The drugs Aricept, Cognex, Excelon, and Reminyl are cholinesterase inhibitors which delay the breakdown of acetylcholine, a chemical in the brain that facilitates communication among nerve cells and is important for memory. Cognex is rarely prescribed due to serious side effects, including possible liver disease. The other three drugs work best when used in the early stage of the disease.

The drug Namenda shields brain cells from overexposure to another neurotransmitter, called glutamate, which contributes to the death of brain cells when produced in excess. It is helpful in the later stages of the disease.

In at least half the patients, drugs do not alleviate the symptoms or halt disease progression.

Additional prescribed medications, including antipsychotics/anxiolytics, antidepressants, and sleeping aids, are given to control symptoms of psychosis, anxiety, depression, and sleeplessness.

Other treatments undergoing research include antioxidants such as Vitamin E, herbs such as Gingko Baloba, Parkinson's drugs such as Cerbex or Eldepryl, prednisone, non-steriodal inflammatory drugs (NSAIDS), and estrogen.

Patients with Alzheimer's Disease Can Use Hearing Aids Successfully:

Researchers at the University of Pittsburgh showed that hearing aids could significantly reduce communication problems for at-home Alzheimer's patients with hearing loss and their caregivers ¹⁹. Their research identified individuals with Alzheimer's disease in the home setting with perceived and measured hearing loss, provided hearing aid amplification management, and evaluated the impact of treatment on caregiver-identified problem behaviors believed to be related to hearing status.

Eight participants were included and 1 to 4 problem behaviors were significantly reduced for each patient after hearing aid treatment. All participants were able to complete the necessary evaluation for hearing-aid fitting and wore their hearing aids between 5 and 15 hours per day by the end of the study.

Researchers at the Manchester Royal Infirmary studied the effects of hearing aids on subjects with mild dementia and hearing loss and found that 42% of subjects showed improvement on an independently rated measure of change ²⁰. The hearing aids were well accepted, and both caregivers and subjects reported overall reduction in disability from the hearing impairment. The researchers conclude that the presence of dementia should not preclude assessment for and use of a hearing aid.

Alzheimer's Disease and Hearing Loss:

No diagnosis of dementia, including Alzheimer's disease, should be made without a complete peripheral and central hearing assessment. Most patients with Alzheimer's disease can be tested for auditory function, either through traditional behavioral methods in the early stages or electroacoustic/electrophysiological methods in the later stages.

Patients with Alzheimer's disease and hearing loss can often use and benefit from hearing aids. Audiologists are essential in the care and management of Alzheimer's patients with hearing loss.

Discussion:

The hope for the future is bright. Current research on Alzheimer's disease seeks better diagnosis, treatment, and vaccine options ¹⁸:

Early diagnosis of the disease will concentrate on (a) seeking biological markers that can be detected in the blood, urine, or spinal fluid, (b) developing more sensitive cognitive tests, and (c) using new imaging techniques such as functional Magnetic Resonance Imaging (fMRI) and Positive Emission Tomography (PET) scans.

Current treatments focus on treating symptoms while future therapies will move toward curative therapies that seek to stop the disease in its tracks.

Although a vaccine is years away, researchers are currently working on altering a vaccine that did seem to clear plaques from the brains of some patients.

References:

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