Premature greying of the hair

• greying of hair is commonly considered a sign of aging
• onset and progress of diffuse greying of hair (canities):
  • the hair greying trait correlates closely with chronological aging and occurs to varying degrees in all individuals, regardless of gender or race. Age of onset also appears to be hereditary, with onset usually in late fourth decade
    • average age for whites is mid-30s, for Asians late-30s, and for Africans mid-40s
    • hair is said to grey prematurely if it occurs before the age of 20 in whites, before 25 in Asians and before 30 in Africans
  • progress of canities is entirely individual; a good rule of thumb is that by 50 years of age, 50% of people have 50% grey hair
    • the darker the hair the more noticeable early greying will be. However, greying can be more extensive in dark hair before total whitening is apparent; the reverse is true for blond hair
    • greying first appears usually at the temples, and spreads to the vertex and then the remainder of the scalp, affecting the occiput last
      • beard and body hair are affected later
        
        
• premature greying of hair
  • while premature canities (greying of hair) may appear without underlying pathology, it has also been associated with:
    • pernicious anemia
    • B12 deficiency
    • hyper/hypo-thyroidism
    • osteopenia (2) - but this association is controversial and there is evidence refuting a link between osteoporosis and premature greying (3)
    • several rare syndromes (e.g. progeria, Werner's syndrome, Cri du Chat syndrome)
    • after beginning chloroquine treatment
    • smoking has been associated with premature greying of hair (4)
  • an acute episode of alopecia areata may result in a very sudden 'overnight' greying (so-called canities subita) that is caused by the preferential loss of pigmented hair in this immune-mediated disorder
    
    
• viligo and premature grey hair (5)
  • however, patients with vitiligo as well as other members of their family frequently have prematurely grey hair. Ordinary greying of hair, representing as it does pigment loss, can be considered a manifestation of the vitiliginous process; in that sense in everyone who lives long enough vitiligo develops. However, most people with grey hair do not have vitiligo of the skin. Many children and teenagers have halo nevi, i.e., hypopigmented rings surrounding dark naevi. Although in most of these people there is no pigment loss in other areas, halo nevi do develop in 50 per cent of the patients with vitiligo
  • vitiligo, and hence premature greying of hair, may be idiopathic but also may be associated with adrenocortical insufficiency, hyperthyroidism, alopecia areata, pernicious anemia, melanoma, scleroderma and morphea (5)

Reference

• 1. Tobin DJ, Paus R. Graying: gerontobiology of the hair follicle pigmentary unit.Experimental Gerontology 2001; 36 (1): 29-54.
• 2.Orr-Walker BJ et al.Pemature hair graying and bone mineral density. J. Clin. Endocrinol. Metab. 1997;82:3580-3585.
• 3. Morton DJ et al. Premature graying, balding, and low bone mineral density in older women and men: the Rancho Bernardo study.J Aging Health. 2007 Apr;19(2):275-85.
• 4. Trüeb RM. Aging of hair. J Cosmet Dermatol. 2005 Jun;4(2):60-72.
• 5. Lerner AB. On the etiology of vitiligo and gray hair.American Journal of Medicine 1971; 51(2):141-8.
• 6.Noppakun N et al. Reversible hyperpigmentation of skin and nails with white hair due to vitamin B12 deficiency. Arch Dermatol. 1986 Aug;122(8):896-9.