Age-Related Neurodegenerative Diseases

In a nutshell

This article gives a brief overview of the mechanisms, symptoms, and possible treatments of the two most common neurodegenerative age-related disorders, such as Alzheimer’s and Parkinson’s disease.
These two ailments are the main cause of dementia in older adults and are the leading causes of disability requiring assistance in daily life.
We highlight scientifically proven lifestyle interventions that have been shown to have a protective role in developing these ailments.

As we grow older, our bodies change. These changes are not limited to the physical appearance of the body but also include changes in all our tissues and organs. Aging is related to the decline in many physiological functions, leading to a higher risk of disease and death.

This article will focus on the main causes and ways of managing neurodegenerative diseases. Neurodegenerative disorders are conditions that involve the progressive loss of function and death of neurons in the brain. Aging is the most common risk factor for developing neurodegenerative diseases, with Alzheimer’s and Parkinson’s diseases being the leading causes of dementia in older people.

Alzheimer’s disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that typically begins gradually and worsens over time. It is caused by the degeneration of the cells in the brain (neurons), and it is the main cause of dementia, which is characterized by a decline in thinking and independence in personal daily activities. This condition is the primary cause of cognitive decline in older adults and is more prevalent in individuals aged 65 and above.

The image shows a progressive shrinkage of the cerebral cortex and hippocampus, two brain areas important for cognition and memory ¹

Main causes of Alzheimer’s Disease

Two main hypotheses are proposed as a cause for AD: cholinergic and amyloid hypotheses.²

The cholinergic hypothesis proposes that Alzheimer’s disease is caused by a deficiency in the neurotransmitter acetylcholine in the brain. Acetylcholine is important for regulating cognitive functions such as memory, learning, and attention. The hypothesis suggests that a decrease in acetylcholine levels results in cognitive impairments and eventually leads to the development of Alzheimer’s disease.

The amyloid hypothesis proposes that Alzheimer’s disease is caused by the accumulation of beta-amyloid plaques in the brain. Beta-amyloid is a protein that is normally cleared from the brain, but in Alzheimer’s disease, it accumulates and forms plaques that disrupt neural signaling and lead to neurodegeneration. This hypothesis suggests that beta-amyloid accumulation is the primary cause of Alzheimer’s disease.

While both the cholinergic and amyloid hypotheses have gained significant attention in the field of Alzheimer’s research, they are not mutually exclusive, and there is evidence to suggest that both mechanisms may contribute to the development of the disease.

Researchers continue to study both hypotheses and investigate potential treatments that target these mechanisms in order to slow or prevent the progression of Alzheimer’s disease.

Risk Factors for Alzheimer’s Disease

The main risk factor for AD is age: usually, symptoms appear at 65-70, but neurological changes occur much earlier. Other factors include genetic predisposition, head injuries, vascular diseases, infections, mental diseases, and environmental and lifestyle factors.

Certain genetic factors, such as mutations in the APP, PSEN1, and PSEN2 genes, have been linked to the development of early-onset Alzheimer’s disease.³ Other genes, such as APOE, are associated with an increased risk of developing late-onset Alzheimer’s disease.⁴

Also, individuals with a family history of Alzheimer’s disease are at a higher risk of developing the condition.

Symptoms of Alzheimer’s Disease

Alzheimer’s is a progressive neurodegenerative disorder affecting the brain, causing cognitive impairment and other symptoms. The symptoms of Alzheimer’s disease generally develop slowly and worsen over time.

In the beginning, individuals with AD may appear healthy but often forget or struggle with some things. Although, initially, they may be aware of their forgetfulness. They might experience other symptoms of minor cognitive decline, like confusion with time and place, impaired judgments, repetitive speech or questions, and trouble learning or remembering new things. Also, changes in behavior and mood are very common for people with AD, including depression, anxiety, aggression, and agitation.

With time the progression of these symptoms increases, and individuals with AD lose their ability to live independently. They may experience difficulty with walking, swallowing, and communicating. In the later stages of the disease, individuals may require assistance with all aspects of daily living.

Treatment of Alzheimer’s Disease

Currently, there is no cure for AD available. Some prescribed drugs (galantamine, rivastigmine, and donepezil) may help reduce or control some cognitive and behavioral symptoms. Non-pharmacological interventions, such as cognitive stimulation therapy, physical exercise, and music therapy, can also help improve cognitive function and quality of life for individuals with Alzheimer’s disease.

Some newly developed treatments that are already FDA-approved tackle the cause roots of AD by removing amyloid plaques (aducanumab), but the research in this direction is ongoing.⁵

Potential Protective Factors and Prevention of Alzheimer’s Disease

One of the main protective factors for AD is a cognitive reserve.⁶ Individuals with a higher cognitive reserve are thought to better compensate for the effects of Alzheimer’s disease and other neurodegenerative disorders.

Several factors contribute to cognitive reserve, including both anatomical and cognitive features. Anatomical features such as brain size and synapse density are thought to contribute to cognitive reserve, as they provide a larger neural network that can support cognitive function. For example, a larger brain may be able to withstand more damage before a cognitive function is affected.

Cognitive features such as educational level, occupational activities, leisure activities, and social engagement are also thought to contribute to cognitive reserve.

Other lifestyle factors that may play a preventive role and lower the risk of developing AD are regular exercise,⁷ diet (Mediterranean diet with plenty of fish oil and vitamins),⁸ the optimal blood level of Vitamin D,⁹ and estrogen (during hormone replacement therapy).¹⁰

Parkinson’s Disease

Parkinson’s disease is a progressive neurological disorder affecting the brain’s ability to control movement and is characterized by cognitive impairment. It is a progressive condition, meaning that symptoms worsen over time.

Causes of Pakinson’s disease

The causes are not fully understood, but reduced dopamine and norepinephrine levels in the brain are found in all patients with PD. In fact, during PD, neurons that produce a neurotransmitter called dopamine gradually die or become impaired. Dopamine is essential for coordinating movement, and the loss of these neurons leads to the characteristic symptoms of Parkinson’s disease, mostly movement impairment. Often, brain cells of PD patients also contain unusual clumps of the protein alpha-synuclein, called Lewy bodies.¹² Although several chemical pesticides have been linked to PD development, genetic factors play the biggest role.

Risk factors of Parkinson’s Disease

The main risk factor is age. Usually, PD develops after the age of 60.

Gender: men are more likely to develop PD than women.

Genetic factors play a role in developing PD. While most cases of Parkinson’s disease are sporadic, meaning they occur randomly without a clear cause, some cases are believed to be caused by genetic mutations that run in families. Lately, a lot of research has been done to find the link between mutations in specific genes and PD risk. Some of these genes include SNCA, PARK2, PARK7, PINK1, and LRRK2.¹³

Head injury: some studies suggest that a traumatic brain injury may increase the risk of developing PD later in life.

Environmental factors: exposure to certain environmental toxins, such as pesticides and herbicides, has been linked to an increased risk of PD.

Symptoms of Parkinson’s disease

The symptoms of PD are divided into motor symptoms and non-motor symptoms.

Motor symptoms include tremors in the hands, feet, or jaw, rigid muscles, unsteady walking, difficulty with balance control, cramps, and spasms, reduced facial expressions, and slurred speech.

Non-motor symptoms include mental health issues (anxiety, apathy, depression), cognitive changes (difficulty thinking, dementia), sleep disturbances, fatigue, digestive problems (constipation, weight problems), and sensory abnormalities (vision changes, smell loss, vertigo).

Treatment of Parkinson’s Disease

No cure is currently available for PD. Treatment is symptomatic, focused on improvement in motor (e.g., tremor, rigidity) and non-motor (e.g., constipation, cognition, mood, sleep) signs and symptoms.

Dopamine-based therapies typically help initial motor symptoms (Levodopa, Neupro, Requip, Mirapex, and Apokyn). Non-motor symptoms require nondopaminergic approaches (e.g., selective serotonin reuptake inhibitors for psychiatric symptoms and cholinesterase inhibitors for cognition). Rehabilitative therapy and exercise are used to complement pharmacologic treatments. Many clinical trials are running to find a disease-modifying treatment, but without much success yet.¹⁴

Potential Protective Factors and Prevention of Parkinson’s Disease

There is no effective approach to the prevention of Parkinson’s disease, but there are some factors that have been shown to have protective effects. They include caffeine, anti-inflammatory drugs, smoking,¹⁵ uric acid (high content in meat),¹⁶ statins,¹⁷ Vitamin D,¹⁸ and regular aerobic exercise.¹⁹

Recap and final thoughts

Both Alzheimer’s and Parkinson’s disease are common neurodegenerative disorders that primarily affect older adults. They can cause dementia and physical impairments that make daily activities challenging. As these diseases progress, patients may require assistance with tasks they could once do independently.

With early diagnosis and appropriate treatment, many individuals with these conditions can maintain a good quality of life and continue to engage in meaningful activities for as long as possible.

Some lifestyle interventions, such as regular exercise, dietary choices (a Mediterranean diet, coffee), and optimal Vitamin D levels, have been shown to lower the risk of developing these ailments. Moreover, engaging in cognitively stimulating activities can play a pivotal role in reducing the risk of developing Alzheimer’s disease, as these activities help to keep the brain active and potentially delay the onset of cognitive decline. To learn some techniques that allow you to offset the start of cognitive decline, please see our article on 12 scientifically-proven techniques.

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