I have countless patients, friends, and family members complaining about how their hair refuses to grow. Then, the comparisons start. “Why do (insert ethnic group) type of people always have such long hair?” This is a troubling issue for many. Fortunately, many studies have looked into this very issue and can give us insights into these quandaries.
Hair length is dictated by the rate of growth and the duration of the growing or anagen phase of the hair cycle. Studies have shown that the rate of hair growth does not greatly vary amongst races. The duration of hair growth before it enters the shedding or telogen phase of the hair cycle is dependent on many factors, mainly genetics. Although, environmental and internal factors also contribute to the rate and duration of the hair cycle.
The anagen phase of hair growth lasts for 2-6 years on average. Clearly, if the rate of growth is constant; then an individual with a 6 year long anagen phase will have significantly longer hair than an individual with a 2 year long anagen phase.
Rate and duration of hair growth really only dictates how long a hair can be potentially. However, hair breakage can obviously shorten hairs and prevent them from appearing to grow longer. This is the main dilemma for individuals who feel their hair is not growing. Hair breakage is ultimately caused by structural weakness in the hair shaft. There are genetic hair shaft abnormalities; however, most are acquired.
The differences in the burden of hair breakage vary amongst races. Comparative studies amongst races on hair structure have shown that individuals of African descent acquire single-strand knots that act as points of weakness. Single-strand knots are not typically seen in Caucasian or Asian hair. Individuals with this problem are basically giving themselves a haircut everytime they comb their hair. This explains why dreads or locks can go grow so long. Unfortunately, relaxing the hair to prevent the knots does not seem to increase length, as the hair has now lost tensile strength due to the harsh chemicals in the relaxers.
Thus, if you are in overall good general health and your hair is not gaining length; lack of hair growth is not generally the issue. The problem lies in acquired hair breakage, most commonly caused by everyday hairstyling practices.
