Adolescent Obesity Associated With Hearing Loss

Obese adolescents are more likely than their normal-weight counterparts to have hearing loss, according to results of a new study. Findings showed that obese adolescents had increased hearing loss across all frequencies and were almost twice as likely to have unilateral (one-sided) low-frequency hearing loss. The study was recently e-published by The Laryngoscope, a journal published by the American Laryngological, Rhinological and Otological Society.

"This is the first paper to show that obesity is associated with hearing loss in adolescents," said study first author Anil K. Lalwani, MD, professor and vice chair for research, Department of Otolaryngology/Head & Neck Surgery, Columbia University Medical Center.

The study found that obesity in adolescents is associated with sensorineural hearing loss across all frequencies (the frequency range that can be heard by humans); sensorineural hearing loss is caused by damage to the inner-ear hair cells. The highest rates were for low-frequency hearing loss - 15.16 percent of obese adolescents compared with 7.89 percent of non-obese adolescents. People with low-frequency hearing loss cannot hear sounds in frequencies 2,000 Hz and below; they may still hear sounds in the higher frequencies (normal hearing range is from 20 Hz to 20,000 Hz). Often they can still understand human speech well, but may have difficulty hearing in groups or in noisy places.

"These results have several important public health implications," said Dr. Lalwani, who is also an otolaryngologist at NewYork-Presbyterian Hospital/Columbia University Medical Center. "Because previous research found that 80 percent of adolescents with hearing loss were unaware of having hearing difficulty, adolescents with obesity should receive regular hearing screening so they can be treated appropriately to avoid cognitive and behavioral issues."

Although the overall hearing loss among obese adolescents was relatively mild, the almost 2-fold increase in the odds of unilateral low-frequency hearing loss is particularly worrisome. It suggests early, and possibly ongoing, injury to the inner ear that could progress as the obese adolescent becomes an obese adult. Future research is needed on the adverse consequences of this early hearing loss on social development, academic performance, and behavioral and cognitive function.

"Furthermore, hearing loss should be added to the growing list of the negative health consequences of obesity that affect both children and adults - adding to the impetus to reduce obesity among people of all ages," said Dr. Lalwani.

In the United States, nearly 17 percent of children are obese, defined as having a body mass index (BMI) of =95 percentile. (BMI in children is expressed as a percentile; adult BMI is expressed as a number based on weight and height.) Obesity and its associated morbidities have been identified as a risk factor for hearing loss in adults.

The study analyzed data from nearly 1,500 adolescents from the National Health and Nutrition Examination Survey - a large, nationally representative sample of adolescents between the ages of 12 and 19, conducted from 2005 to 2006 by the National Center for Health Statistics of the Centers for Disease Control and Prevention. Participants were interviewed at home, taking into account family medical history, current medical conditions, medication use, household smokers, socioeconomic and demographic factors, and noise-exposure history.

Dr. Lalwani and his colleagues speculate that obesity may directly or indirectly lead to hearing loss. Although additional research is needed to determine the mechanisms involved, they theorize that obesity-induced inflammation may contribute to hearing loss. Low plasma levels of the anti-inflammatory protein adiponectin, which is secreted from adipose tissue, have been found in obese children, and low levels in obese adults have been associated with high-frequency hearing loss (which affects a person's ability to understand speech). Obesity also may contribute indirectly to hearing loss as a result of its comorbidities, including type 2 diabetes, cardiovascular disease, and high cholesterol - all of which have been reported to be associated with loss of peripheral hearing (relating to the outer, middle, and inner ear).

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CNIO Researchers Discover A New Gene Involved In Obesity

RAP1 is a gene that also protects telomeres. This is the first time that a link has been found between these structures that shorten with ageing and obesity

The discovery of an unexpected function for a gene that was associated to another process in the organism might be a solution in search of a problem, a clue to unsuspected connections. That is what has happened with RAP1, a gene that protects telomeres - the ends of chromosomes - after researchers from the Spanish National Cancer Research Centre (CNIO) surprisingly discovered its key role in obesity.

"We still don't know what evolutionary significance to attach to it, but it is at the very least interesting that a telomere gene is related to obesity", says Maria Blasco, CNIO director and co-author of the study published in the journal Cell Reports.

RAP1 forms part of the shelterin complex, a group of proteins that make up the protective hood of telomeres - the DNA sequence at the ends of chromosomes that shortens with each cellular division and thus measures the ageing of the organism. There are six shelterins, and CNIO's Telomeres & Telomerase Group, which studies them in-depth, has discovered that RAP1, contrary to the rest, is not essential for the survival of the organism; but that does not mean RAP1 is not important. The reverse is rather the case: when comparing the genomes of different species, it can be observed that RAP1 is the most conserved shelterin of all. Despite the long history of evolutionary changes, RAP1 has not changed; it is present even in yeast. This normally implies an important role in the organism, but which one?

CNIO researchers had discovered that RAP1, in addition to being located in telomeres, is also present in the rest of the chromosome; they supposed it acts regulating the action of other genes. In order to analyse this other potential function, and its importance in the organism, CNIO researchers created a lineage of mice without RAP1 and, to their surprise, discovered a model for obesity.

MICE LACKING RAP1 GAIN MORE WEIGHT

"Mice - especially female mice - without RAP1 do not eat more, but do gain weight. They suffer from metabolic syndrome, accumulate abdominal fat and present high glucose and cholesterol levels, amongst other symptoms", says Paula Martínez, first-author of the study.

The reason is that RAP1 plays an important role in the regulation of genes involved in metabolism. In particular, researchers have discovered that it acts on the same signalling pathway mediated by another protein: PPAR- gamma (PPAR-?). In fact, PPAR-? deficient mice suffer from a type of obesity "surprisingly similar" to that seen in mice without RAP1.

The next step in the research will be to study if RAP1 also plays a role in human obesity. "This discovery adds an element to the obesity equation, and opens up a possible new link between metabolic dysfunction and ageing, via a protein present in telomeres", says Blasco.

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Your Weight, Eating Behavior, Likely Impacted By What You Believe Causes Obesity

Whether a person believes obesity is caused by overeating or by a lack of exercise predicts his or her actual body mass, according to new research published in Psychological Science, a journal of the Association for Psychological Science.

Obesity has become a pressing public health issue in recent years, with two-thirds of U.S. adults classified as overweight or obese and similar trends unfolding in many developed nations. Researchers Brent McFerran of the Ross School of Business at the University of Michigan and Anirban Mukhopadhyay of Hong Kong University of Science and Technology wondered whether individual beliefs might play a role in these trends.

From an initial online survey, they discovered that people seem to subscribe to one of two major beliefs about the primary cause of obesity:

"There was a clear demarcation," says McFerran. "Some people overwhelmingly implicated poor diet, and a roughly equal number implicated lack of exercise. Genetics, to our surprise, was a far distant third."

McFerran and Mukhopadhyay wanted to dig deeper to see if the pattern could be replicated and, if so, what implications it might have for behavior. They conducted a series of studies across five countries on three continents.

Data from participants in Korea, the United States, and France showed the same overall pattern: Not only did people tend to implicate diet or exercise as the leading cause of obesity, people who implicated diet as the primary cause of obesity actually had lower BMIs than those who implicated lack of exercise.

"What surprised me the most was the fact that we found lay theories to have an effect on BMI over and above other known factors, such as socio-economic status, age, education, various medical conditions, and sleep habits," says McFerran.

The researchers hypothesized that the link between people's beliefs and their BMI might have to do with how much they eat.

A study with Canadian participants revealed that participants who linked obesity to lack of exercise ate significantly more chocolates than those who linked obesity to diet. And a study with participants in Hong Kong showed that participants who were primed to think about the importance of exercise ate more chocolate than those primed to contemplate diet.

These findings provide evidence that our everyday beliefs about obesity may actually influence our eating habits - and our body mass.

According to Mukhopadhyay, this is "the first research that has drawn a link between people's beliefs and the obesity crisis, which is growing as fast as people's waistlines are."

The new findings suggest that, in order to be effective, public health campaigns may need to target people's beliefs just as much as they target their behaviors.

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