While numerous papers have reported on the biological mechanisms of human hair pigmentation and graying, epidemiological description of graying process and especially the definition of early hair graying remain scarce.
Although there are some arguments, a rule of thumb is that by 50 years, 50% of people have 50% gray hair.[5
] As previously stated, graying is related to ethnic and geographical origin and indeed, hair is said to gray prematurely only if graying occurs before the age of 20 years in whites, before 25 years in Asians and before 30 years in Africans.[10
] On the other hands, some authors believe that early hair graying is defined a priori as the majority hair graying(>70%) before age 40 year.[8
This study compared the clinical and radiologic severity of the patients with knee OA between those with early hair graying and those without it. To the best of our knowledge, no study was found showing this correlation, but similar studies have been carried out on the correlation between early hair graying and other diseases.
A recent study showed that individuals with early hair graying (with no other risk factors) were 4 times more likely to have osteopenia than individuals without hair graying.[7
] There was an obvious correlation with familial osteoporosis, too. It may be concluded that early hair graying could account for a small part of the difference in bone mineral density within the population.[8
Another study reported a lower correlation between early hair graying and early cardiovascular disease, perhaps it should be considered as a risk factor for coronary disease and used to recognize individuals at increased risk.[9
We compared the clinical severity and radiologic severity of knee OA between the two groups generally and under the breakdown of age group (in three subgroups of age: 30-40 year, 41-50 year, 51-60 year). In the age group 30-40 year, we had 3 patients in the case group with significant knee OA in two of them (KL = 3, KL = 4). In the control group, we had no case in this age group that had the inclusion criteria to be enrolled in study. Therefore, due to the impossibility of statistical analysis between these two groups and the possibility of error, this age group was excluded from the study.
As it showed in Tables and , the amount of WOMAC index in the case group is greater than that in the control group either generally and under the breakdown of age groups. However, the differences are not significant statistically.
As you can see in , severity of radiographic changes in the case group are significantly greater than that of the control group (P < 0.02). With regard to , we can conclude that the significant differences are related to the age group 41-50 year. In the age group, 51-60 year, despite the greater KL grade in the case group in comparison to the control group, their differences are not significant statistically.
Comparison of the grade of KL scale between case and control groups under the breakdown of age group
Based on these preliminary data, we can conclude that even at the same age of OA onset, the rate of progression of OA and the grade of joint destruction in individuals with early hair graying are greater than normal individuals, but this effect on functional status is inconsiderable.
Whether early hair graying correlates definitely with early joint cartilage aging remains unclear. It can be due to the limited study time and small sample size. Furthermore, in this preliminary study, we just evaluated patients referring with clinical OA and early radiological findings in younger asymptomatic individuals with early gray hair should be evaluated in future studies to better determine this basic hypothesis.