What is mild cognitive impairment (MCI)? It is a good question, for the parameters are fuzzy. MCI is a hodgepodge of terminology including amnestic and nonamnestic types, with the amnestic type possibly leading to dementia. It is defined as a disorder, but not a disease, that is between normal aging and dementia. As a disorder, it may be more easily reversed. The number of people affected is difficult to pin down, but estimates range from 14 to 22 percent of the U.S. population aged 70 and older (1). Risk factors for MCI include increased age; family history; chronic diseases including heart disease, high blood pressure and diabetes; drug therapies; and lifestyle (2).
So is being overweight potentially detrimental, or is it being underweight? In short, when you are obese and lose weight, it actually decreases your risk. It is not difficult to understand when you put it into context, which we will do.
Also, are there ways to decrease your risk? Well, I already mentioned one, weight loss for the obese patient. I will delineate how weight loss could be both beneficial and detrimental. Another is a twist on a Mediterranean-type diet.
So without further ado, let’s look at the research. Most of the studies refer to dementia; remember, MCI is a malady not a disease; therefore it is harder to find specific studies relating to increased risk.
Rarely does it seem that being overweight or obese is beneficial. Dementia is no exception. I know I am using the risk of dementia study, but I want to demonstrate that the overweight and obese individuals, who now make up at least two-thirds of the U.S. population, are jeopardizing their cognitive abilities.
In an observational study using the Swedish Twin Registry, results showed that being overweight or obese in midlife significantly increased dementia risk — a 71 percent increase in the overweight patient and an almost fourfold increase in the obese (3). This may be a powerful reason to watch your weight at any age.
If being obese or overweight may be harmful, what about being underweight? According to the results of a retrospective (backward-looking) study from the UK Clinical Practice Research Datalink, those who are underweight have a 34 percent increased risk of dementia and are at greater risk than those who are overweight or obese (4). In fact, this study suggests that those who are overweight and obese are at lower risk for dementia than even those who are normal weight.
But wait, how can that be? Didn’t the study above suggest that being overweight was bad? First impression says that either the study focusing on overweight/obese patients was wrong or this study has a caveat. Well, the latter is the case. In fact, the researchers did not delineate among potential causes for patients to be underweight or even normal weight. Many times, patients are underweight or normal weight at middle to advanced years due to weight loss-inducing chronic diseases, such as cancer and autoimmune diseases. Underweight was defined as a BMI <20 kg/m2. Other previous studies also contradict the obesity paradox seen in this study.
Unintended weight loss
In one recent study, results demonstrated that unintended weight loss from midlife to later life is a potentially ominous sign for increased risk of mild cognitive impairment (5). There was a statistically significant difference between those who were at higher risk of developing MCI because of greater unintentional weight loss and those who did not experience as much weight loss. The absolute difference was 0.8 kg and the increased risk was 4 percent; however, in a subgroup with a 5-kg weight loss every 10 years, there was an almost 25 percent increased risk of mild cognitive impairment. At the beginning of the study, none of the patients had MCI, and the average age was 70 years. The researchers used retrospective data to compile weight loss from midlife.
Possible solutions to the rescue
What can be done about this? There are lifestyle changes, including dietary changes and weight loss that may help to reduce the risk or even reverse MCI.
Weight loss, intentional that is!
On the flip side to unintended weight loss, there is intentional weight loss in those who are obese. In a recent randomized controlled trial (RCT), results showed that those who were treated with a calorie-restricted diet saw improvements in language, memory and executive functioning (allows one to complete tasks or reach goals) compared to those in the conventional medicine treatment group without diet counseling (6). The study population had a mean age of 68 and included 80 participants with 40 participants in each arm. It was composed of 80 percent women. Those in both groups were obese, ranging in BMI from obese to morbidly obese, 30-49.5 kg/m2.
The goal was to reach 10 percent weight loss with most of these women, though that was not achieved. This study used a calorie-restricted diet to achieve weight loss. About 40 percent of the participants did lose 5 percent of weight during the study’s one-year duration. The good news: Even with this modest 5 percent weight loss, there was improvement in cognition, especially verbal memory, which involves remembering words and utilizing language skills. The more weight they lost, the better they did cognitively (a dose-response curve). This is encouraging for a follow-up study with more significant weight loss.
Mediterranean diet with extra fat
Recently, we have been furiously debating the importance of fat in the diet. In an RCT, results showed that adding extra virgin olive oil (EVOO) or nuts to the Mediterranean-type diet increased participants’ cognitive functioning (7). There were three groups; all were on the Mediterranean diet, but the two treatment groups differed — one had added EVOO and the other had added nuts.
Interestingly, nuts and olive oil had different effects. The group that had nuts, consisting of one ounce per day of a mixture of almonds, walnuts and hazelnuts, saw an improvement in word memory.
Meanwhile, those in the EVOO group saw more gains in thought processing, executive functioning in the frontal cortex. The EVOO group consumed five tablespoons of olive oil a day, or one liter a week. This is a large amount of olive oil. Remember, though, that the brain is made up of 70 percent fat. There were a total of 447 study participants with a mean age of 67 years, and the study duration was pretty long at approximately four years. No participant had mild cognitive impairment at the start of the trial, though they were at high risk for cardiovascular disease.
Although there was significant improvement in cognition in the treatment groups compared to the control, there was no difference in occurrence of MCI. Overall incidence of MCI was very small across the groups. A good follow-up study might be a group eating a Mediterranean diet with olive oil plus nuts.
A diet high in “good” fats, especially a Mediterranean-type diet with either nuts or olive oil, appears to be beneficial to improve cognition in older adults.
(1) Arch Neurol. 1999;56(3):303; Ann Intern Med. 2008;148(6):427. (2) uptodate.com. (3) Neurology. 2011;76(18):1568-1574. (4) Lancet Diabetes Endocrinol. 2015;3(6):431-436. (5) JAMA Neurol. online Feb. 1, 2016. (6) J Clin Endocrinol Metab. online Dec. 29, 2015. (7) JAMA Intern Med. 2015 Jul;175(7):1094-1103
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, go to the website www.medicalcompassmd.com or consult your personal physician.