There is growing evidence to suggest that consideration should be given to cognitive function as a risk factor in patients with obesity.
When we think about patients with obesity, we tend to think primarily about how weight affects cardiovascular, endocrine, digestive, or skeletal systems. However, there is growing evidence to suggest that consideration should also be given to cognitive function as a risk factor in patients with obesity, particularly in the context of Alzheimer’s disease. There is substantive empirical evidence speaking to the relationship between obesity and vascular and metabolic commodities such as insulin resistance, hyperglycemia, and type 2 diabetes.
The link between Alzheimer’s and Obesity
Over one’s lifespan, a higher BMI has been linked to decreased cognitive performance, cognitive decline, reduction in white matter, and a decrease in the integrity in the blood-brain barrier. There is a clearly established relationship between obesity in midlife and the onset of Alzheimer’s disease in late-life. For patients with obesity in midlife (mean age of 50), there is a 40 percent increased risk of dementia. In addition to obesity in mid-life, high cholesterol and high systolic blood pressure are part of the additive effect of Alzheimer’s risk factors. However, the relationship between BMI and Alzheimer’s disease in later life is more complex.
Insulin Resistance and Alzheimer’s Disease
An insulin resistance state in the brain has been linked to Alzheimer’s disease, and insulin resistance has been shown to be an early marker of Alzheimer’s. Insulin resistance in middle age can increase one’s risk of Alzheimer’s disease, most probably through decreased brain glucose metabolism and dysfunctional brain insulin signaling. This results in increased amyloid deposition and decreased brain volume.
Hyperglycemia, Type 2 Diabetes, and Alzheimer’s Disease
There is solid evidence to suggest type 2 diabetes increases the risk of Alzheimer’s disease in patients with obesity. Research suggests that this risk may be increased by the degree of hyperglycemia. For example, in older patients with HbA1c levels ≥ 6.5 percent, their risk of Alzheimer’s disease increased 2.8-fold; in patients with HbA1c levels ≥ 7 percent, the risk increased by 4.7-fold.
Encouraging and Supporting Healthy Weight Loss in Patients
While there is still more to learn and currently no known effective treatment or effective way to prevent Alzheimer’s disease, clinicians should continue to encourage and support healthy weight loss among their patients with obesity. Interestingly, bariatric surgery has been found to improve memory and executive functions, cognitive processes which are compromised in Alzheimer’s patients. However, in patients with a family history of Alzheimer’s disease, the improvements were not seen. Dietary interventions have also resulted in cognitive improvements.
The metabolic corrections following weight loss, though not causally related to preventing Alzheimer’s disease, do represent a potentially fertile approach to warding off Alzheimer’s disease. Intentional weight loss in patients with obesity has been shown to improve cognitive functions, specifically improvements in attention, executive functioning, and memory. Medically supervised weight management programs, such as Very Low Calorie Diets or Low Calorie Diets, have been shown to yield positive metabolic corrections. While the relationship between Alzheimer’s and weight remains unclear, it is clear that maintaining a healthy weight confers benefits in cognitive function.