Research suggests that hair color, hair dyeing, and perspiration can bias hair test results regarding drug exposure, but research is needed to examine such associations in a multivariable manner. In this epidemiology study, adults were surveyed entering nightclubs and dance festivals in New York City, and 328 provided hair samples, which were analyzed using ultra-high-performance liquid chromatography–tandem mass spectrometry to determine the level of detection of cocaine and 3,4-methylenedioxymethamphetamine (MDMA). Reporting use was not an inclusion criterion for analysis. We used two-part multivariable models to delineate associations of hair color, past-year hair dyeing, and frequency of past-month hat wearing (which may increase perspiration) in relation to any vs. no detection of cocaine and MDMA as well as level of detection, controlling for hair length, self-reported past-year cocaine/ecstasy/MDMA use, and age, sex, and race/ethnicity. Those reporting having dyed their hair were at increased odds of having any level of cocaine detected (adjusted odds ratio [aOR] = 3.75, 95% CI confidence interval [CI]: 1.85–6.70), and compared to those with brown hair, those with blond(e) hair on average had lower levels of cocaine (ng/mg) detected (beta = -7.97, p = 0.025). Those reporting having dyed their hair were at increased odds of having any level of MDMA detected (aOR = 3.05, 95% CI: 1.44–6.48), and compared to those who reported never wearing a hat, those who reported wearing a hat daily or almost daily on average had lower levels of MDMA (ng/mg) detected (beta = -6.61, p = 0.025). This study demonstrates the importance of using multivariable models to delineate predictors of drug detection.
A multivariable analysis delineating hair color, hair dyeing, and hat wearing as predictors of level of cocaine and MDMA detection in human hair samples
Drug Testing and Analysis [Epub 2023 Nov 20]. doi: 10.1002/dta.3607.