PT Classroom - Summary of Alzheimer’s Disease and Implications for Physical Therapy  ׀ by David Carrubba, SPT


As the average life expectancy of humans continues to increase so does the risk of developing Alzheimer’s disease (AD) and other forms of dementia or mild cognitive impairment (MCI). As people get older, they are also more likely to suffer falls or injuries that require medical care to return to function (Shumway-Cook & Woollacott, 2017). With increased likelihood of physical therapists to have exposure to patients with complex medical conditions, clinicians must be prepared to recognize how the intersection of these conditions is likely to affect treatment and be prepared to adjust accordingly. This article briefly explores the characteristics of AD as well as how physical therapists may assist with the prevention and management of symptoms.

Although the root cause of AD is not completely understood, the disease is most notably characterized by the accumulation of a sticky molecule called Amyloid-Beta Peptide (AB) onto neurons and vascular structures in the brain. AB is difficult for the body to remove once it is cleaved from its precursor protein and results in inflammation triggered by surrounding glial cells. As inflammation becomes chronic, the induced anaerobic environment in the brain results in edema and apoptosis in neural structures. Another characteristic of AD is the buildup of hyperphosphorylated tau proteins within neurons which result in neurofibrillary tangles (NFT). These tangles inhibit the transport of nutrients to and from the soma and ultimately leads to neuronal death (McGough et al., 2017).

Risk factors, Prevalence, Incidence
AD has several modifiable and nonmodifiable risk factors. As of 2021, there is estimated to be 6.2 million Americans living with AD who are older than the age of 65 with the prevalence of people with AD doubles for every 10 years of life from the age of 65 (5.3% cases) to 85 (34.6% of cases). Women appear to be more susceptible to the disease than men (61% women, 39% men in 2021) (Alzheimer’ Association, 2021). People with Down Syndrome are reportedly 50% likely to develop AD as they age because the allele which is responsible for the production of AB is located on chromosome 21. The accumulation of BA plaques and neurofibrillary tangles has been found before the age of 40 in this patient population (NIH, 2020).

Although a small percentage of the cases of AD have familial or genetic links, there are several modifiable risk-factors that can be addressed to protect against developing AD or slowing the progression of the disease including smoking, physical inactivity, hypertension, obesity, diabetes, and low educational attainment (McGough et al., 2017).

Signs and Symptoms
People with AD demonstrate signs and symptoms that progressively interfere with their ability to function independently and participate in normal daily activities. These include memory loss, decreased planning- or problem-solving skills, difficulty completing familiar tasks, confusion, deceased perception of visual and spatial relationships, word finding in speaking or writing, frequently misplacing things, decreased judgment, social withdrawal, and mood and personality changes (Alzheimer’s Association, 2017).

People with dementia are also effected by several motor signs as well including gait disturbances, extrapyramidal motor impairment, rigidity, and postural instability. These motor signs all significantly increase falls risk and decrease ability to participate in daily activities. Kato-Narita & Radanovic, 2009).

If a patient is demonstrating the hallmark signs and symptoms of dementia, it is likely that they have lived with the disease for several years already. Several studies reported detecting biomarkers of the disease between 13-22 years before the expected onset of symptoms (Alzheimer’s Association, 2021). An AD diagnosis in patients older than 65 years old typically results in death 4-8 years later, although its has been reported some individuals living an additional 20 years (Alzheimer’s Association, 2021).

Screening and Diagnostic Imaging
High risk patients demonstrating signs and symptoms of AD can be screened for cognitive function using multiple validated tests of global cognitive function. Two recommended tests are the Mini-Mental Status Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). The MMSE can be administered in under 10 minutes and demonstrates high test-retest and interrater reliability. Baek et al. (2016) found the MMSE to be useful for discriminating patients with MCI from those with AD as well as healthy older adults from those with AD. They also reported a likely ceiling affect of those with higher educational attainment (Baek et al. 2016). The Montreal Cognitive Assessment has been tested to demonstrate higher reliability than the MMSE for detecting mild cognitive decline and AD. Freitas et al. (2013) determined the sensitivity and specificity at cut-off scores of 22 for MCI and 17 for AD to be 81%/77% and 88%/98%, respectively. Cut-off scores using the MMSE for were 29 for MCI and 26 for AD and the sensitivity and specificity was 67%/72% and 85%/93%, respectively (Freitas et al., 2013). Trzepacz et al. (2015) further supports the use of the MoCA over the MMSE due to its inclusion of items measuring executive function, higher-lever language, and complex visuospatial processing. They also recommend MoCA in conjunction with other functional tests to detect early MCI sooner than with the MMSE (Trzepacz et al., 2015). McGough et al. (2017) reported that motor signs often present years before the onset of dementia and that slowed gait speed was found to be a strong predictor of future cognitive decline. This researcher also supports the suggestion of Trzepacz et al. (2005) by reporting that the combination of slowed gait and cognitive complaints is a stronger predictor of cognitive outcomes than either measure on its own (McGough et al., 2017).

Positron Emission Testing (PET) is a nuclear imaging modality that can be used to detect both AB and NFTs. A positive test for AB typically shows deposition in the precuneus, orbitofrontal cortex, and inferior temporal and posterior cingulate gyrus. Later stage AD will show additional deposition in the prefrontal, lateral temporal, and parietal cortices. Although a negative amyloid PET scan can differentiate other forms of cognitive impairment from AD, a positive test is not sufficient evidence to establish an AD diagnosis because many elderly people with normal cognition also present of elevated AB (Marcus, Mena, & Sybramaniam, 2014). Amyloid PET scans are typically indicated for people demonstrating symptoms of early onset AD (<65 years old) or test positive for cognitive assessment screens with atypical clinical presentation of symptoms. This imaging modality is considered inappropriate for people over the age of 65 who meet expected clinical criteria for AD, people solely with genetic risk factors (presence of APOE-4 gene, Down Syndrome), and those with cognitive complaints but have not been confirmed with cognitive screening (Marcus, Mena, & Sybramaniam, 2014).

Treatment and Prevention
Physical therapy intervention for patients, with or without symptoms of AD should be directed at restoring and/or preserving function and participation in meaningful activity. As previously mentioned, AD risk is strongly tied with smoking, physical inactivity, hypertension, obesity, diabetes, and low educational attainment (McGough et al. 2017). With appropriate patient education and maintenance of a regular exercise program, physical therapists can help manage or eliminate many modifiable risk factors to preserve physical and cognitive function and possibly even delay the onset of AD symptoms.

Regular exercise provides abundance of protective mechanisms against the neurodegenerative processes observed in the onset of AD. Aerobic exercise is attributed to increased levels of Brain-Derived Neurotropic Factor (BDNF), which is a neurotransmitter in the brain that aids with glucose control and provides neuroprotective properties. Aerobic exercise also increases neurogenesis in the hippocampus which may preserve and/or improve memory and learning. Resistance training increase levels of insulin-like growth factor 1 (IGF-1) which inhibits apoptosis and aids in maintaining neuroplasticity. Other benefits of regular exercise including increased cerebral blood flow, increased vascular health and compliance, reduced mean arterial blood pressure, and decreased systemic inflammation directly and indirectly aid in AD prevention and/or delay of symptoms by managing potential modifiable risk factors (McGough et al., 2017). These benefits have been observed in patients following exercise programs consistent with recommendations made by the American College of Sports Medicine and American Heart Association: 150 minutes of moderate-intensity or 75 minutes vigorous intensity aerobic exercise weekly in addition to strengthening exercises performed twice weekly (McGrough et al., 2017).

People with AD become a significant falls risk over time due the progressive onset of motor symptoms, visuospatial decline, decreased judgement, and muscular atrophy due to decreased activity (McGrough et al., 2017). Kato-Narita & Radanovic (2009) found that 80% of patients with AD, despite stage of condition, experienced falls within their own homes. Most of these falls (43.1%) were due to environmental hazards followed by instability (22.6%) and dizziness (11.3%). More than 1 in 5 falls were considered “ignored” due to lack of patient recall and absence of caregiver (Kato-Narita & Radanovic, 2009). In attempt to improve or delay falls risk status, physical therapy intervention can be aimed at reducing falls risk through dual-task based training to improve gait, balance, and postural control. In a retrospective analysis, Longhurst et al. (2020) found treatment sessions that incorporated dual tasking into aerobic activity (20-25 minutes), strengthening (15-20 minutes), and balance training (15-20 minutes) significantly improved AD patient outcomes beyond the MCID and MDC for MoCa, 6-Minute Walk Test, Mini Balance Evaluation Systems Test, and Five Times Sit-to-Stand test. Roughly 75% patients with AD and 80% of patients with MCI improved in at least one outcome measure for gait, balance, or cognition (Longhurst et al., 2020). This research suggests dual-task training in conjunction with aerobic exercise, strength training, and balance training may be more effective at preserving cognitive and physical function for patients with AD prior to or in the early in the onset of symptoms.

AD is a neurodegenerative disease that primarily effects the elderly causing progressive decline physically, socially, and cognitively. Once an AD diagnosis is established, symptoms typically become fatal within 10 years, with the much of the time being spent in the care of nursing staff. Because the disease usually progresses silently for several years before the onset of symptoms, clinicians should seek to eliminate modifiable risk factors in all patients, especially those 65 years of age and older. By providing education about the importance of eliminating risk factors and helping patients adhere to a regular exercise program, physical therapists can allow patients to have greater opportunity and independence with participating in activities that are meaningful to them for a longer period of time.


Last revised: 12/22/21
by David Carrubba, SPT

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