About 37% of Britons aged 61 to 70 and 60% of those aged 71 to 80 - 6.5m people - have age-related hearing loss.
The Human Mutation study of over 1,200 people found subtle changes in a gene called KCNQ4 were more common in those with age-related hearing problems.
Based on this study, common age related hearing loss appears likely to be due to a combination of environmental (e.g. exposure to loud sounds) and genetic factors. The gene KCNQ4 has previously been linked to a hereditary form of hearing loss that strikes young people, regardless of exposure to loud sounds. This doesn't mean that exposure to loud sounds won't cause hearing loss - it will. Instead, the way I interpret the study, it is more likely that if KCNQ4 is seriously defective then hearing loss strikes early; if it is a defective to a "lesser" extent, then one is more succeptible to age related hearing loss; and, finally, if it is normal, one can still lose hearing due to loud sounds (and maybe through other mechanisms, such as age related degradation of tissues and such in the ear).
Note: The above is my own interpretation and is meant to estimate a trend, based on experience and scientific reasoning, and may not be fully supported by existing data.