Jun 05 2014
One of the more common complaints I see in my clinical practice is subjective memory impairment (SMI) – the perception of poor concentration and short term memory. SMI is distinguished from full-blown dementia in that the mental status exam and diagnostic tests are normal, but the symptoms can still be significant.
Once an underlying disease or specific pathology has been ruled out, the working diagnosis for SMI is that it is functional, meaning that it is a symptom of some process that is temporarily impairing brain function but not causing permanent or progressive brain damage. The task then becomes to identify any lifestyle factors that may be causing SMI.
A recent study published in PLOS One sheds further light on such risk factors. The authors conducted a survey of 18, 614 people of various ages and asked questions about memory and behaviors. They found:
Depression, less education, less exercise, and hypertension were significantly associated with SMI in all three age groups. Several interactions between risk factors were significant in younger and middle-aged adults and influenced their associations with SMI. Frequency of SMI increased with age and number of risk factors. Odds of having SMI increased significantly with just having one risk factor.
This fits other data, and also conforms to my clinical experience. Most young adults I see with memory complaints do not have Alzheimer’s disease or any other similar disease. The most common associated symptom is depression, which is what the researchers found also.
Depression is known to cause memory difficulty, which is called pseudodementia because it can look clinically similar to dementia (although it is possible to tell the difference just on exam).
One problem, however, is that correlation does not tell what the causation is. Most people will feel that they are depressed because of their memory difficulty, and not the other way around. The only way to confirm that the depression is the primary problem is to treat the depression. If the memory symptoms resolve as the depression gets better, that confirms the diagnosis.
Being mentally and physically active also have a host of benefits, including improved memory function, even delaying or mitigating full dementia. Depression can further reduce physical and mental activity, and may be acting through these other lifestyle factors.
I was surprised that the authors did not ask about sleep in their survey. Poor sleep is strongly correlated with a host of functional symptoms, including SMI. In fact, it’s possible in many patients that poor sleep in the primary problem.
In practice we consider poor sleep, depression, and lack of exercise and mental engagement to all be co-morbid – meaning that they are all working together and you can’t cleanly separate out which factor is causing the other. Poor sleep causes depression and lack of exercise which both further worsen the sleep, leading also to obesity which worsens sleep and further makes exercise difficult, etc.
Therefore, in practice, it seems prudent to simultaneously address all of the possible risk factors. This means optimizing sleep, getting regular exercise, staying mentally active and socially engaged, treating depression if necessary, and improving diet to address any nutritional factors and help with weight management.
In a way memory is a canary in the coalmine – even a slight impairment in brain function will often be noticed. Despite the popularity of the notion that we only use 10% of our brains (although it is just as popular to debunk this myth), the evidence overwhelmingly suggests that we are using our brains to capacity, and that anything that degrades brain function even a little has a measurable affect on performance.
This is not true of most organs. You can lose half your kidney function and not notice, for example.
So, when people are stressed, not sleeping well, not exercising, having poor nutrition, smoking, perhaps using alcohol or other drugs, the brain will often be the first organ to manifest symptoms. The first symptom to appear will likely be poor concentration, as that is a high energy function.
I often see patients with SMI who want me to find “the” cause of their symptoms, as if it’s a bug or other external problem. Sometimes they are even disappointed when the workup is negative (even though this is the best possible outcome).
This latest study supports other research in suggesting that lifestyle factors are often the culprit. The answer, therefore, is lifestyle adjustments. That can be challenging for many people, however – especially those very people who are at risk for developing such symptoms in the first place.
It seems like prudent advice, therefore, to advocate good lifestyle habits before they get to the point where functional impairment begins. Obviously, no one should smoke, the evidence on that is clear. If you drink, do so in moderation.
The other two factors for which there is a great deal of evidence everyone should pay attention to are – exercise regularly, and put a high priority on getting enough and high quality sleep. I will add – don’t overuse caffeine (1 8oz beverage per day is a good rule of thumb). It worsens sleep, can cause headaches, and actually has a net negative impact on your energy levels.
The good news is that each lifestyle factor can have a beneficial effect on the others – regular exercise, for example, improves sleep. The spiral can go in a good or bad direction.
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