“There’s a growing body of evidence linking elevated blood sugar to memory problems.” (NPR, 2013)
“Insulin resistance is usually at or near the top of the list of known lifestyle-related factors heightening the risk of declining cognition in the elderly.” (Cunnane et al., 2011)
“… even in the absence of manifest type 2 diabetes mellitus or impaired glucose tolerance, chronically higher blood glucose levels exert a negative influence on cognition, possibly mediated by structural changes in learning-relevant brain areas.” (Kerti et al., 2013)
The link between chronically elevated blood glucose, insulin, and increased risk for Alzheimer’s disease and other forms of cognitive decline is becoming undeniable. It’s not for nothing that Alzheimer’s disease is now regularly referred to as “type 3 diabetes” or “brain insulin resistance” in the scientific literature. With this in mind, any interventions that improve insulin sensitivity and help restore and maintain healthy blood sugar levels should, at least in theory, be beneficial for reducing risk. Unfortunately, this is proving not to be such a slam dunk.
A study out of the UK recently published in the BMJ concluded that a moderate to high intensity aerobic and strength training program did not slow the progression of cognitive impairment in subjects with mild to moderate dementia. The subjects—approximately 500 individuals, mean age 77 years old—did exhibit improved physical fitness, but this did not lead to improved scores or even unchanged scores on the Alzheimer’s disease assessment scale-cognitive subscale (ADAS-cog). In fact, scores actually worsened for those in the exercise group compared to those of subjects in the usual care (no exercise) group, albeit only slightly.
The intervention consisted of “group sessions in a gym twice a week for four months; each session lasted 60 to 90 minutes. We also asked the participants to do home exercises for one additional hour each week during this period. The supervised programme lasted four months, after which we prescribed a more frequent home based programme with a target of unsupervised physical activity or exercise of 150 minutes each week (total).” The aerobic portion included static cycling, while the resistance training portion included handheld dumbbells for various upper body exercises and a weighted vest for lower body movements, including sitting-to-standing. After the supervised four months, subjects were to continue the exercises as able, with a median follow-up approximately a year after initiation of the program.
It’s possible the exercises weren’t intense or powerful enough to have a beneficial impact on cognitive function, behavior, or performance of daily life activities. This seems unlikely, however, given that improvements in physical fitness were noted. Also noted, though, were more than 25 adverse events, including worsening hip pain, two injurious falls, and one hospitalization for exercise-induced angina. Obviously, a thorough assessment should be done before anyone of any age increases their physical activity, but this is especially true of older individuals with any degree of cognitive impairment.
These lackluster findings are disappointing. The exercise program in this study not only failed to improve cognitive function in individuals with mild to moderate dementia, but it may have actually negatively impacted it, leading the investigators to conclude, “Moderate to high intensity aerobic and strength exercise cannot be recommended as a treatment option for cognitive impairment in dementia.”
At first, this may seem somewhat surprising. After all, numerous epidemiological studies indicate that those who exercise may have lower risk for cognitive decline, and mechanistic studies suggest exercise is instrumental for supporting neuroplasticity and preventing cognitive decline. However, it may be that exercise and/or regular physical activity during the course of a lifetime offers some degree of protection or reduced risk, but once someone is already afflicted with dementia, it may be a case of “too little, too late” with regard to getting the horse back into the barn after the door’s been open for a while.
It’s been shown that “you cannot outrun a bad diet” when it comes to obesity. Perhaps the same is true of cognitive decline and dementia: you can’t out-exercise the negative effects of a poor diet on brain health. If insulin resistance and elevated blood glucose—even within what’s typically considered the “normal” range—are risk factors for dementia and Alzheimer’s, then it stands to reason that exercise alone wouldn’t be enough to turn the tide on these insidious conditions.
Maintaining insulin sensitivity and controlling blood sugar are ground zero for potentially staving off cognitive decline. Exercise can and should be a part of this, but by itself, it likely won’t be sufficient. A good foundation would be some variation of a reduced carbohydrate diet, tailored to an individual’s unique level of carb tolerance and insulin sensitivity, with exercise included as an additional facet of a multipronged strategy, along with adequate quantity and quality of sleep, stress management, and other interventions that beneficially impact glucose and insulin dynamics in the body. Researchers note: “…strategies aimed at lowering glucose levels even in the normal range may beneficially influence cognition in the older population, a hypothesis to be examined in future interventional trials.” It would be interesting to see the results of a long-term, prospective cohort study of a Paleo, low carb, or ketogenic diet for reduction of risk for cognitive decline.