About278 million people worldwide suffer severe hearing loss. Two thirds of theaffected belong to the developing world, and live with their economic andeducational opportunities limited by hearing disability. Lack of adequaterehabilitation services haunts low-income countries.
Amiddle ear infection called chronic otitis media is responsible for most of thecases of hearing loss in children living in poverty. Chronic otitis mediaaffects between 1.4% and 7.8% children in South East Asia. It is not knownwhether nutritional deficiency increases susceptibility to ear infections;evidences are scanty. Southern Asia is a land where vitamin A deficiency andhearing loss coexist, and are widely prevalent. About 45% of vitamin Adeficient preschool children in the world reside here.
VitaminA is a nutrient known to have multiple protective effects on immune system. Itboosts host's defence mechanisms by maintaining the integrity of protective linings.Vitamin A regulates immune processes and modulates oxidative stress. Thesemechanisms may let the nutrient control inflammatory processes that damage theear and impair hearing. Deficiency of vitamin A disrupts the protective coveroffered by mucus-secreting epithelium.
Researchersstudied the effect of high dose (200 000 IU, dose was reduced in children lessthan 1 year) vitamin A during the preschool years on hearing loss in earlyadulthood. The study was conducted in Nepal; an estimated 32% of its preschoolchildren are affected by vitamin A deficiency. Eight percent children aged 5 to15 years in Nepal have a diagnosis of hearing loss. Loss of hearing disruptsnormal activities of daily living and socialisation.
Highdose vitamin A supplementation in early childhood was found to reduce the riskof hearing loss from middle ear infection in adolescence and young adulthood.The risk of hearing loss was reduced by 42% following nutrient supplementationin those who had ear discharge in childhood. Although literature over the past80 years had suggested the protective effect of vitamin A, this could be thefirst study to demonstrate protection conferred by vitamin A against hearingimpairment of likely infectious origin.
Byregulating the host defense mechanisms, vitamin A reduces the severity ofmiddle ear infection. The current finding is an additional public healthindication for vitamin A prophylaxis. Vitamin A prophylaxis programmer has beenoperational in India since 1970. It was originally started with the aim ofpreventing blindness in children.
The now proven protective effects of vitamin A in preventinghearing loss is a cue for the authorities to strengthen vitamin Asupplementation in early childhood in areas of high deficiency.
Reference:VitaminA supplementation in preschool children and risk of hearing loss as adolescentsand young adults in rural Nepal: randomised trial cohort follow-up study; JaneSchmitz et al; BMJ2012;344:d7962