Obesity in mid-life is associated with a higher risk of dementia- including Alzheimer’s disease (AD) – later in life. Though age is still the primary risk factor for dementia, lifestyle factors such as nutrition and physical activity may play an important role in the onset of cognitive impairment and dementia. Now, weight loss surgery is showing benefits in cognitive decline.

Evidence has connected obesity, high blood pressure, elevated cholesterol, and increased blood glucose levels – collectively known as metabolic syndrome – to the onset of dementia even decades down the road. The connection is complicated and still unclear, but there is hope that shared signaling pathways may be a therapeutic target for metabolic syndrome and certain types of dementia. Diabetes mellitus, smoking, and a sedentary lifestyle are also associated with an increased risk of dementia.

Recently, several studies linked weight loss after bariatric surgery to improved cognitive function; the results are being extrapolated to offer hope for dementia prevention and treatment.

One study evaluated the brain functions of 17 obese women before and 24 weeks after gastric bypass surgery. The brain functions of 16 normal-weight women were also evaluated as controls. Before surgery, the obese women showed higher metabolic activity in the posterior cingulate gyrus – an area of the brain already implicated in the pathology of dementia. This extra metabolic activity was not present after surgery and the post-surgery levels of activity were not different than those of the lean women. After surgery, the obese women also showed improvements in executive functions such as planning, organizing, and strategizing. The authors claim that the evidence suggests that, in obesity, the brain must work harder to achieve the same level of cognition as in an individual of healthy weight.

Another study evaluated 78 patients who underwent bariatric surgery. One year after surgery, cognitive function was markedly improved. This improved cognition was associated with improved liver function, as well, suggesting that liver function impacts cognition in obese patients. A similar study of 50 post-bariatric surgery patients revealed that cognitive improvements were maintained 3 years after surgery.

The impacts of weight loss without surgery on dementia are not as clear. In several cases, low body mass index or weight loss in the early stages of cognitive impairment actually led to worse outcomes and faster disease progression.

Approximately 66 million people are expected to have dementia by 2030 and the condition will continue to impose social, psychological, and financial burdens on families and society. But, together, these new findings are offering glimpses into the pathways of disease progression and future therapeutic targets for dementia. For now, we can just add cognitive decline and dementia to the already long list of complications associated with poor lifestyle choices.

Maintaining a healthy body weight as young as 30 years old may offer the best protection against cognitive decline, but, for those who are obese at the onset of cognitive decline, weight loss surgery may offer cognitive improvement in addition to the obvious physical improvements.

References

Alosco ML, Galioto R, Spitznagel MB, Strain G, Devlin M, Cohen R, Crosby RD, Mitchell JE, & Gunstad J (2014). Cognitive function after bariatric surgery: evidence for improvement 3 years after surgery. American journal of surgery, 207 (6), 870-6 PMID: 24119892

Alosco ML, Spitznagel MB, Strain G, Devlin M, Cohen R, Crosby RD, Mitchell JE, & Gunstad J (2014). The effects of cystatin C and alkaline phosphatase changes on cognitive function 12-months after bariatric surgery. Journal of the neurological sciences PMID: 25073570

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