Frontotemporal Dementia Linked to Abnormal Eating

February 10, 2016

The first study to investigate eating patterns in frontotemporal dementia (FTD) in a scientific manner has found that patients with this disorder do have clear-cut inappropriate dietary habits.

The study, published online in JAMA Neurology on January 25, showed that different types of FTD were associated with different eating behaviors. While patients with the behavioral FTD variant were found to excessively overeat, particularly consuming high-sugar foods, patients with semantic dementia demonstrated very rigid behavior, sometimes only eating one particular type of food.

Brain imaging also suggested that these eating patterns were controlled by complex brain networks rather than one particular brain structure.

"Inappropriate eating patterns have been commonly observed in patients with FTD, but they have not been so rigorously scientifically studied before," lead author, Rebekah M. Ahmed, MBBS, Neuroscience Research Australia, Sydney, commented to Medscape Medical News. "We used a study design similar to that used and validated in obesity research to gauge eating behaviors in these patents and found very clear results."

She noted that FTD is the second most common cause of young-onset dementia (under age 65 years), typically seen in individuals in their 50s and 60s. There are several types of FTD; the behavioral variant manifests as prominent inappropriate personality and behavior, including loss of empathy, executive functioning, and ability to plan, whereas semantic dementia causes patients to lose the meaning of words.

"In our study, these two different variants were associated with distinctly different eating behaviors," Dr Ahmed said.

"If we can understand which brain networks are controlling these inappropriate eating behaviors, this may help in the development of treatments for the condition," she added.

"Metabolic changes occurring in the body may be affecting disease progression, and treating the early behaviors may slow disease progression. Or, it is also possible that the specific eating patterns may have some protective role in FTD," she said. "We need to study whether we can modify the eating behaviors and if this makes any difference."

For the study, eating behavior was recorded in 49 patients with three different types of dementia (19 with behavioral FTD, 15 with semantic dementia, and 15 with Alzheimer's disease) and compared with that in 25 healthy controls.

All participants fasted overnight and were then offered a buffet breakfast and allowed to eat for half an hour. The researchers calculated the total amount of food eaten and recorded which types of food were eaten.

Results showed that all the patients with behavioral-type FTD consumed more calories than the other participants, taking in a mean of 1344 calories, compared with 710 calories in the Alzheimer's group, 573 calories in the semantic dementia group, and 603 calories in the control group (P < .001).

Dr Ahmed also pointed out that the calorie intake of the patients with behavioral FTD did not cross over with the other groups. "The behavioral patients who ate the least still consumed more calories than participants from other groups who ate the most."

In contrast, patients with semantic dementia did not overeat but instead showed rigid eating behavior, often refusing to eat the food on offer. One patient ate nothing, and others ate very small amounts. "These patients were very fussy and would often only eat certain things," Dr Ahmed commented. "For example, one woman would only eat fruit."

Sugar Cravings

For the second part of the study, the patients were given a sucrose preference test in which they were asked to taste three versions of the same dessert, which contained 26%, 39%, or 60% sucrose, and asked to select the one they liked the most.

The patients with behavioral FTD showed a strong preference for the dessert with the highest sugar content, more so than the other groups. Five patients with semantic dementia refused to partake in this experiment, stating that they did not like the dessert, but those who did take part also tended to favor the sweetest dessert.

Dr Ahmed noted that sugar craving appears to be a particular characteristic of behavioral type FTD. She commented: "Sugar cravings are a common condition, but in these behavior type FTD patients it is excessive. Some consume 1 kilogram of sugar a week. They eat huge amounts of chocolate or other sweet food. It is not unusual for them to eat several liters of ice cream a week or a whole large packet of biscuits in one go."

She also explained that while patients with behavioral FTD do frequently have higher than average body mass index, it is not as high as would be expected for people consuming this amount of food.

Noting that some crossover may exist between behavioral FTD and amyotrophic lateral sclerosis (ALS), Dr Ahmed reported that ALS is known to be associated with hypermetabolism, which was the subject of a review by her group in recently published in Lancet Neurology.

"So it is possible that these FTD patients may also have changes in their metabolism that might be causing the overeating," she said.

MRI Findings

The researchers also studied the brains of the participants by using MRI to look for unusual patterns in specific areas of the brain that correlated to particular behaviors.

They found that the overeating in the patients with behavioral variant FTD is associated with complex networks in the brain involving several different areas, including those involved in reward, autonomic function, and vision, rather than just a single brain structure.

The researchers also found activity in different regions of the brain associated with abnormal eating behaviors in patients with semantic dementia, suggesting different mechanisms at play in the two variants of FTD.

They report that many of the same brain structures that are core to the semantic deficits seen in semantic dementia appear to be involved in the eating patterns in this group of patients, suggesting a contribution of semantic networks to eating control, possibly secondary to the loss of knowledge concerning foods.

In an accompanying editorial, Jennifer L. Whitwell, PhD, Mayo Clinic, Rochester, Minnesota, says Dr Ahmed and colleagues "should be applauded for performing such detailed and prospective assessments of eating behaviors in FTD," noting that this is also the first study that specifically assessed MRI correlates of eating behavior separately within patients with behavioral FTD and semantic dementia.

"The findings extend and quantify previous observations of overeating in bvFTD [behavioral FTD] and show that a preference for sweet foods is observed in both bvFTD and SD [semantic dementia]," she says.

Dr Whitwell also points out that the findings of strong associations between both caloric intake and sucrose preference and the occipital lobe and cerebellum were surprising because these regions of the brain are not typically associated with FTD.

"The authors may have uncovered a previously unrecognized role for these structures in FTD, suggesting autonomic and visual contributions to problems with eating," she notes.

This work was supported by a grant from the National Health and Medical Research Council of Australia (NHMRC); a grant from the Australian Research Council Centre of Excellence in Cognition and its Disorders Memory Node; and a project grant from the NHMRC to Forefront, a collaborative research group dedicated to the study of frontotemporal dementia and motor neuron disease. The authors have disclosed no relevant financial relationships.

JAMA Neurol. Published online January 25, 2016. Abstract Editorial

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