Altitude may contribute to regional variation in methamphetamine use in the United States: a population database study.

OBJECTIVE: Methamphetamine (MA) use rates in the United States (US) have consistently demonstrated geographical variation and have been higher in the West and Midwest. This uneven pattern of use could be explained by regional differences in MA manufacturing and distribution, but may also result from differences in altitude. The hypobaric hypoxia found at high altitude alters neurotransmitter synthesis in the brain, which may contribute to MA use. The present study investigated the relationship between mean altitude and MA use rate in the 48 contiguous US states and the District of Columbia.

METHODS: State-level estimates of past year MA use were extracted from the National Survey on Drug Use and Health report. The mean altitude of each state was calculated using the Shuttle Radar Topography Mission altitude data set.

RESULTS: There was a significant positive correlation between mean state altitude and MA use rate (r=0.66, p<0.0001). Multivariate linear regression analysis showed that altitude remained a significant predictor for MA use rate (β=0.36, p=0.02), after adjusting for age, ethnicity, education, socioeconomic level, employment, MA laboratory incidents, subpopulations, and other substance use.

CONCLUSION: Altitude appears to a possible contributing factor for regional variation of MA use in the US. Further studies will be required to determine biological changes in neurotransmission resulting from chronic mild hypoxia at high altitude in MA users.