Gray Hair

Motivation: For the past two days, I was caught in the blizzard at Minneapolis and spent a lot of idle time reading newspapers at the airport.  One of the faces that caught my attention was that of the WikiLeaks founder Julian Assange - his hair is just so white.  Even looking around the airport, I saw that hair graying proceeds at remarkably different rates.  We all associate hair graying with ageing, but is it also linked with diseases of ageing like vascular disease?  Turns out that this issue has also been studied.

Paper: "Gray hair, baldness, and wrinkles in relation to myocardial infarction: The Copenhagen City Heart Study", Schnohr, P. et. al. American Heart Journal, 1995 (130): 1003-1010.  http://www.ahjonline.com/article/0002-8703(95)90201-5/abstract?source=aemf

Method: The Cophenhagen City Heart Study is a prospective study of 20,000 adult men and women.  In the study, 7,163women and 5,837 men were physically examined between 1976-1978.  Five years later, the subjects were again examined (91% follow-up rate).  Incidence of death and MI were ascertained from questionnaires and from hospital records.  During physical exam, gray hair, baldness, wrinkles, ear lobe crease, and arcus senilis were noted.  Follow-up time for patients was on average 12 years.

Results:
The paper provides excellent statistics of the prevalence of gray hair, baldness, wrinkles, etc. divided by gender and age groups (really interesting), but I will skip to the meat of the matter regarding correlation.  Overall, in the observed time period, women suffered from 226 MI and men suffered from 524 MI.

Gray hair: After adjusting for known risk factors including age, smoking, BMI, cholesterol, etc., a significant correlation existed for men but not for women.  For men, the relative risk was 1.4 (CI: 0.9-2.0) for moderately gray hair and 1.9 (1.2 to 2.8) for completely gray hair.  For women, the relative risk was 1.1 (0.7-1.6) for moderately gray hair and 1.4 (0.9-2.0) for completely gray hair.  Note that in the subgroup, about 25% of women dyed their hair and had to be excluded.  Among women, dyeing hair did not increase incidence of MI, RR - 1.3 (0.6-2.7).

Baldness: Frontoparietal region baldness was associated with incidence of MI in men but not in women.  In men, the relative risk was 1.6 (1.1-2.3) compared to men with no bald triangle.  No significant association was found in crown-top baldness.

Wrinkles: Facial wrinkles over all age groups were not significantly associated in either sex with MI.  For subjects younger than 55,  in men but not women, severe facial wrinkles were associated with MI, RR for men 1.6 (1.1-2.3).

Conclusion: At least in men, after adjusting for conventional known risk factors of MI, completely gray hair was associated with increased risk of MI.  While the same association did not hold true for women, the case is a bit murkier.  First of all, women, as expected, experienced fewer MI than men.  Also, a large fraction of women (~25%) used hair dyes and had to be excluded, which biased the analysis.  So, graying hair may still be a risk factor or may not be a risk factor for women.  Other interesting results were that frontoparietal baldness and severe facial wrinkling in subjects younger than 55 were both associated with MI in men rather than women.  These results suggest that craniofacial ageing may result from different processes in men and women.

Overall, this was one of the largest prospective studies examining the issue of clinical ageing signs and MI.  But, as with any prospective studies, the presence of confounders cannot be ruled out.