Secular change in heights of indigenous adults from a Zapotec-speaking community in Oaxaca, southern Mexico.

Secular change in adult height of residents in a rural indigenous community in the Valley of Oaxaca was evaluated. Subjects were measured in 1971 (49 males, 26 females 19-70 years), 1978 (128 males, 124 females 19-82 years) and 2000 (155 males, 255 females 19-89 years). Heights were adjusted for estimated loss with age using two protocols; height at 21 years of age was also estimated. The effects of age and secular factors on measured and adjusted heights were evaluated through segmented linear regressions for three birth periods, <1930, 1930 through 1959 and >or=1960 which approximate significant periods in Mexican history. Secular increase in height occurred but estimated rates varied over time and between sexes. Males born before 1930 showed a secular increase in height but females did not. Adults of both sexes born 1930-1959 showed secular gains and estimated rates did not differ. The secular gain in height continued among those born 1960 and later and estimated rates were similar in both sexes. Estimated height at 21 years of age increased in males (not significant) but not in females born before 1930, showed little or no change in those born between 1930-1959, and increased (not significant) in those born 1960 and later. Combining observations on adults with those for youth in the community indicated several phases of secular change in height that varied with years of birth.