Age at menarche amongst school girls in a high altitude Nigerian town.

Menarche, the first menstrual period is believed to be influenced by many factors including altitude. The data of 331 school girls in Jos (1,300 m above sea level), a high altitude Nigerian town, that attained menarche between January 1989 were analysed. The mean menarcheal age for these school girls is 13.21 +/- 1.01 years. This value was not significantly different from 13.02 +/- 1.28 years found amongst school girls at Calabar (20 m above sea level) a Nigerian sea level resident sample. Perhaps, Jos is not situated at a high enough altitude to significantly affect the age at which menarche is attained.