Many people notice that they become more forgetful or have trouble thinking as they get older. However, it’s important to know that not all memory or thinking changes are normal aging. If you or a loved one experiences sudden or significant changes, it’s always best to seek medical evaluation. In some cases, these symptoms may be caused by infections, medication side effects, depression, vitamin deficiency, thyroid disease, brain tumors or head injury. Some of these are preventable or treatable, including exercise, a healthy diet, proper sleep and taking your medications as prescribed.

In general, the brain deteriorates with age due to a process called neurodegeneration. This occurs when neurons die, which leads to a decrease in mental functions, such as memory, language, decision-making and visuospatial function. The cause of these changes is often a result of damage to the grey matter, which comprises the cortex and thalamus, or the white matter, which covers the connections between them.

The same brain changes that lead to motor problems in PD also can lead to slowness of thought and difficulty processing information (termed bradyphrenia). These are examples of cognitive changes that are common in PD, though not all people with PD experience them. The most commonly affected cognitive domains in PD are attention and working memory, and executive and visuospatial functions.

Some people with PD are more likely to develop dementia, which is a progressive and irreversible decline in mental abilities. It’s usually the result of several underlying conditions, such as neurodegenerative disease and certain types of small-vessel disease. Dementia can also occur from traumatic brain injury, and some chronic diseases or illnesses, such as heart disease, diabetes, high blood pressure, stroke, head injury or infection of the coverings of the brain and spinal cord (meningitis).

Seek prompt medical care if you notice that your thinking or memory have changed. Your doctor will ask you questions about your past health, family history and current medications and treatments. Your doctor will do a neurological exam, looking at your face, neck and trunk. He or she will also perform tests to look for an underlying cause of your symptoms. You may be referred to a neurologist or a neuropsychologist for further evaluation and possible treatment. A therapist who specializes in speech and/or occupational therapy can help with communication and other strategies to improve daily functioning. Some of these therapies can be done in your home. A physiotherapist can help you learn exercises to keep your muscles strong, which can reduce the impact of cognitive changes. A dietician can help with diet. A psychologist can help with stress and depression.