Hope of reversing hearing loss in old age has been raised by scientists in the US. They have found the genetic “master switch” that controls the development of crucial cells that transmit. These so called “hair cells” release neurotransmitter chemicals that transmit sound signals to the brain via the auditory nerve. This could eventually lead to treatment that would reprogramme stem cells or other cells in the ear to replace those that die. In Britain, some 40% of 50 year olds and 70% of over 70s suffer some degree of hearing loss. (Accompanying image by James Musallam via Wikimedia Creative Commons)