Researchers at the Brigham and Women's Hospital have discovered that overweight women may be
more likely to develop hearing loss.
Hearing Loss vs. BMI: A Study
Researchers at Brigham and Women’s Hospital in Boston wanted to find out if Body Mass Index (BMI) was correlated with hearing sensitivity, as reported in
previous findings from the University of Antwerp and the
Health ABC Study.
As part of an
extended research project called Nurses' Health Study II, researchers documented the BMI, waist circumference and physical activity of female nurses for a decade, between 1989 and 2009. Participants included 116,430 women aged 25-42, from 14 different states.
The women were given a series of questionnaires in which they were required to detail their routine physical activities, such as running, hiking, bicycling and tennis, as well as how many flights of stairs they climb daily. In 2009 the participants were given a questionnaire asking if they had experienced any hearing issues.
Of the 80,696 participants who responded, about 23 percent reported hearing loss, and on average these people had a higher BMI.
Findings: Hearing Loss Risk
Higher BMI and larger waist circumference were correlated with an increased risk of hearing loss, according to the study. Women with optimal weight (BMI lower than 25) were at a relatively low risk for hearing loss, whereas overweight women (BMI greater than or equal to 25) had a higher risk of hearing loss. Very severely overweight women (BMI greater than or equal to 40) had the highest risk for
hearing loss.
Similarly, women with smaller waists (smaller than 71cm) had a low risk of hearing loss compared to women with a waist circumference greater than or equal to 71 cm. Women having a waist circumference larger than 88 cm were the most likely to experience hearing loss.
Increased physical activity was also associated with a lower risk of hearing loss. Women that walked for two or more hours per week were less likely to experience hearing loss and interestingly, the intensity of the physical activity made no difference. That is, running and jogging reduced the risk of hearing loss by the same amount as walking did.
Why Hearing Loss?
The researchers explain that the biological basis behind obesity and the effect that physical activity has on hearing may be due to
hypoxia,
ischemic damage, and
oxidative stress, medical conditions that can damage the cochlear and spiral ganglion cells necessary for hearing.
They also note that obesity can cause
atherosclerosis, or an accumulation of plaque in the arteries, and this can lead to the hardening and tightening of the auditory nerve as well as constriction of cochlear blood flow.
Simply put, conditions like obesity can result in a loss of blood flow to the cochlea, causing cell death. Activities like running and jogging may increase blood flow to the cochlea, protecting against cell damage. The surprising results of this study reveal yet another health complication associated with obesity and support the idea that maintaining a healthy weight and even moderate physical exercise can have lasting health effects.
