For many people, one of the most concerning non-motor features of Parkinson’s disease (PD) is cognitive decline. Attention, working memory, executive function, memory, language and visual reasoning are the cognitive skills most frequently affected in PD which can be concerning because these skills allow us to perform daily functions such as paying attention, solving problems, remembering where items are and how to do certain tasks.

Cognitive changes can be an intrinsic part of PD, caused by abnormal accumulation of the protein alpha-synuclein into Lewy bodies in the thinking areas of the brain. When this occurs, there are strategies ranging from cognitive therapy to medications to help support cognitive function which you can read about here.

Today’s blog will focus on a different angle – on the vast array of treatable medical problems that can worsen cognitive function. These factors are crucial to identify, because if they are treated, cognitive function may improve.

Hearing Loss & Cognitive Decline

I will start off by discussing one factor that is rarely mentioned in discussions of cognitive decline in PD, but is a highly treatable contributor to cognitive difficulties – hearing loss. Abundant research exists that supports the claim that hearing loss impacts cognitive function. The connection was recently highlighted in in the New York Times and in the Wall Street Journal.

One Johns Hopkins research study reviewed thousands of medical claims and demonstrated an association between hearing loss and an increased 10-year risk of dementia, falls, depression and heart attack. Research also suggests that improving hearing with hearing aids can improve cognitive function. One study showed that memory decline slowed in patients who started wearing hearing aids, highlighting the importance of detecting and treating hearing loss early.

How can hearing loss contribute to cognitive decline?

It makes sense that hearing trouble can impact cognition. People who do not hear well:

• do not participate in conversation and limit their social and cognitive engagement, which can contribute to cognitive decline.
• use more cognitive energy to decipher the sounds that they are hearing. This leaves less cognitive power for other tasks.
• will have a hard time remembering what they hear.

If those around you tell you that your hearing appears to have diminished, get your hearing evaluated with an audiogram. Improving your hearing with hearing aids could have many positive impacts on your well-being, and potentially improve cognitive functioning as well.

Other possible contributors to cognitive decline in Parkinson’s

Hearing is not the only modifiable contributor to cognitive decline. Consider reviewing this list with your doctor to make sure that you do not need to be evaluated for any of these conditions:

• Medication effects – The first step to take when cognitive difficulties are identified is to review all of your medications with your doctors. Certain medications given for urinary frequency, migraine, seizures, anxiety, and other conditions, can interfere with cognitive function or make your thinking feel sluggish. Even some medications given for PD can contribute to this problem, so be sure to review your medication list frequently with your neurologist and speak up if you’re noticing changes in your cognitive abilities. If a medication is identified that can worsen cognitive function, it can be changed.
• Intercurrent infection – If cognitive difficulty (or hallucinations) seem to start or worsen quickly, it is important to check for a urinary tract infection or pneumonia. If an infection is identified, it can be treated with antibiotics.
• Depression – It is well established that depression can mimic cognitive decline. When someone is depressed, he/she tends to withdraw socially and not exert themselves cognitively. When this occurs, the condition is referred to as pseudo-dementia, and with proper treatment of the depression, cognitive function can be restored.
• Abnormal thyroid function – Cognitive difficulties can result from too little thyroid hormone which can be easily checked with a blood test and corrected with a prescription of synthetic thyroid hormone.
• Abnormal Vitamin B12 levels – Cognitive difficulties can also result from low levels of Vitamin B12. This can also be easily checked with a blood test and corrected by taking supplemental Vitamin B12.
• Orthostatic hypotension – Periodic drops in blood pressure may occur as a non-motor symptom in PD which you can read about here. During periods of low blood pressure, cognitive function may decline because of decreased blood flow to the thinking parts of the brain. If this is suspected, have someone take your blood pressure sitting and standing during these times. An array of treatments for orthostatic hypotension ranging from lifestyle changes to prescription medications can help this situation and hopefully improve cognitive function.
• Dehydration – Dehydration can exacerbate low blood pressure and can contribute to changes in alertness.
• Vascular brain health – Poor circulation of blood to the brain, often due to narrowed or damaged arteries from high blood pressure, high cholesterol and diabetes, can cause strokes. Strokes can be apparent and result in a sudden neurologic deficit such as the inability to move one side, or to speak. Strokes can also be silent and not cause any noticeable neurologic deficit, if they affect areas of the brain that are not involved in particular functions. However, an accumulation of both these types of strokes can contribute to cognitive decline. Improved diet, exercise, and good control of blood pressure, cholesterol and diabetes can help stave off this contribution to cognitive decline.
• Poor sleep and sleep apnea – Poor sleep from Parkinson’s disease typically leads to daytime fatigue which can make cognitive tasks more difficult. Sleep apnea, which often is suspected due to persistent, loud snoring, is one cause of poor sleep which has an increased incidence in people with PD. In the general population, this condition is often associated with obesity, with fat deposits in the upper airway resulting in obstruction of normal breathing at night. In PD however, the condition may be due to a combination of factors including rigidity, hypokinesia and postural abnormalities of the trunk muscles as well as autonomic dysfunction. Another contributor to the disordered breathing of PD may be abnormal signaling from sleep and respiratory centers in the brain. Regardless of the cause, in this condition, there are frequent awakenings during the night, due to intermittent starts and stops of breathing and resultant episodes of drops in blood oxygen levels. Typically, the person is not aware of the frequent awakenings because they are so brief, but they can lead to an increased risk of heart disease and stroke, as well as increased cognitive problems. Sleep apnea can be diagnosed with a polysomnogram or sleep study, in which sensors are placed on the scalp and body during sleep to record breathing patterns, oxygen levels, brain activity, heart rate, blood pressure and body movements. This test provides a lot of information and is most accurate when done at a sleep center, although there are very simplified at-home versions, which capture far less information, but that may suffice for some people.  If sleep apnea is detected, it can be treated with an array of breathing devices which can supports breathing at night.
• Head trauma – as you may be aware, past head trauma likely contributes to a small increased risk of PD. When cognitive changes occur, they may be related to a more acute head trauma. A fall which results in hitting the head, for example, may cause bleeding in various areas in and around the brain. Usually, it will be clear that a trip to the emergency room is necessary because of changes in consciousness. Sometimes, however, the injury may seem mild even though it caused internal bleeding. For example, bleeding in the subdural space around the brain could be slow and subtle and result in cognitive changes that develop over weeks to months. Therefore, it is generally recommended that after even minor head injury if there is headache, vomiting, short-term memory loss, seizure or visible trauma above the collar bone, a computed tomography (CT) of the head is performed.

Tips and Takeaways

• Although cognitive decline can be a feature of PD itself, there may be other medical issues that are contributing. Being evaluated for these issues is crucial as modifying them can have a positive impact on cognition and your quality of life.
• Therefore it’s very important that you tell your doctor about any changes you notice (or that loved ones point out) in your cognitive function so potential corrective action can be taken as early as possible.
• Hearing loss can be a treatable contributor to cognitive decline. If hearing loss is suspected, consider asking your doctor for a referral for an audiogram. Hearing aids will likely improve your well-being and may improve cognitive decline as well.
• There are many other treatable contributors to cognitive decline including: medication effects, infection, thyroid abnormalities, low Vitamin B12 levels, strokes, head trauma, orthostatic hypotension, and sleep apnea.