There is a correlation between the incidence of grey hair and the age of
the individual. Data from Keogh, E.V. and Walsh, R.J. Nature. 207, 877,
1965 reported the incidence of grey hair in an Australian population.
Male 25-34 Any greying 22%, complete greying 0.23%; Male 35-44, Any 61%,
complete 2.2%, Male 45-54 Any89%, complete13%, Male 55+, Any 94%, complete
30%. Parallel data for females.
For more complete information see my chapter"Skin changes as a reflection
of biologic age" in Practical Handbook of Human Biologic Age Determination
, AK Balin, ed. CRC Press 1994, 525 pages.