Several studies have shown that certain girls, particularly African-American girls, experience puberty earlier than others

African-American women tend to begin menstruating four to six months earlier than girls of European descent. Later in life African-American women also have a higher risk for obesity, hypertension, and metabolic disorders including diabetes. These two trends could be related and genetic factors could be a common denominator. A new study of African-American women looked specifically at genetic variations contributing to age at menarche. The research, done by a multi-institutional team of scientists, crunched data from 15 different studies, which included information from over 18,000 women. Certain diseases are more prevalent in certain populations. For instance, African-American men are more likely to develop and die from prostate cancer than people of European descent. African Americans also tend to be at higher risk for type 2 diabetes, while people of European descent are at higher risk of the heart rhythm disorder atrial fibrillation. In this case study, the researchers performed a meta-analysis of existing research to search for DNA variants associated with earlier menarche in African-American women and then compared their results to data from women of European descent. The variants, called SNPs (or single-nucleotide polymorphisms), can account for some of the differences in biological traits, in this case early menarche, between two individuals. These variants in turn can help scientists identify the genes and biological mechanisms controlling menarche timing. Out of 42 SNPs associated with age at menarche in European women, 25 were also associated with the trait in African-American women, bolstering the evidence that these genes genetic variants are tied to menarche timing. However, they also found variants in eight regions of the genome that were more strongly associated with age at menarche in African-American women than in European-American women. Many of these regions contain genes that influence obesity, underscoring the link between body fat and early menarche. Other regions include genes associated with breast and other cancers.