Symptoms including paranoia, amnesia, cerebellar malfunction, and lethargy can also manifest when undergoing histidine treatment. Future research
Every year, more than 200,000 individuals see their physicians concerning chemosensory problems, and many more taste disturbances are never reported. Due to the large number of persons affected by taste disorders, basic and clinical research are receiving support at different institutions and chemosensory research centers across the country. These taste and smell clinics are focusing their research on better understanding the mechanisms involved in gustatory function and taste disorders such as dysgeusia. For example, the National Institute on Deafness and Other Communication Disorders is looking into the mechanisms underlying the key receptors on taste cells and applying this knowledge to the future of medications and artificial food products. Meanwhile, the Taste and Smell Clinic at the University of Connecticut Health Center is integrating behavioral, neurophysiological, and genetic studies involving stimulus concentrations and intensities in order to better understand taste function. See also
Anosmia
Parosmia

References
External links
Dysgeusia at NIH
Once the loss has progressed to the 2–4 kHz range, there is increased difficulty understanding consonants. Both ears tend to be affected. The impact of presbycusis on communication depends on both the severity of the condition and the communication partner.Older adults with presbycusis often exhibit associated symptoms of social isolation, depression, anxiety, frailty and cognitive decline. The risk of having cognitive impairment increased 7 percent for every 10 dB of hearing loss at baseline. No effect of hearing aids was seen in the Lin Baltimore study. Causes
The aging process has three distinct components: physiologic degeneration, extrinsic damage (nosocusis), and intrinsic damage (sociocusis). These factors are superimposed on a genetic substrate, and may be overshadowed by general age-related susceptibility to diseases and disorders. Hearing loss is only weakly correlated with age. In preindustrial and non-industrial societies, persons retain their hearing into old age. In the Framingham cohort study, only 10% of the variability of hearing with age could be explained by age-related physiologic deterioration. Within family groups, heredity factors were dominant; across family groups, other, presumably sociocusis and nosocusis factors were dominant. Heredity: factors like early aging of the cochlea and susceptibility of the cochlea for drug insults are genetically determined. Oxidative stress
General inflammatory conditions

Sociocusis
Sociocusis is the condition of those who have hearing loss attributed to continuous noise exposures, unrelated to their job or occupation. This exposure to these stimuli is frequent, and are often considered common "background noises" that affect the hearing abilities of individuals.