Asthma and geographical altitude: an inverse relationship in Mexico.

Motivated by the great asthma-prevalence variation throughout the world, we analyzed the rate variation of medical services due to asthma in the 32 Mexican states at the Instituto Mexicano del Seguro Social (approximately 24 million insured subjects). In 1993, a total of 406,036 services were due to asthma, and state rates ranged from 53 to 476 x 10,000 insured subjects. A direct correlation (p < 0.05) was found for single-room house, ascariasis, and rubella rates, but the strongest (inverse) correlation was found for geographical altitude (r = -0.73, p < 10(-5)). Thus, in Mexico, geographical altitude affects the etiological factor(s) responsible for the development of asthma or for the triggering of asthma attacks.