Risk factors for developing eosinophilia myalgia syndrome among L-tryptophan users in New York

Area of Science:

• Epidemiology
• Toxicology
• Medical Science

Background:

• Eosinophilia myalgia syndrome (EMS) is a serious condition linked to L-tryptophan (LT) supplementation.
• The exact cause of EMS remained unclear, prompting investigations into LT product contaminants.

Purpose of the Study:

• To investigate the association between specific L-tryptophan (LT) products and the development of eosinophilia myalgia syndrome (EMS).
• To identify potential risk factors and manufacturing sources linked to EMS outbreaks.

Main Methods:

• A case-control study design was employed, comparing patients diagnosed with EMS who had used LT with LT users who did not develop EMS.
• Product tracing was conducted to identify the bulk manufacturer of LT supplements used by both cases and controls.
• Statistical analysis, including odds ratios (OR) and confidence intervals (CL), was used to assess risk factors.

Main Results:

• All EMS cases (100%) and a majority of controls (73%) used LT traced to Showa Denko K.K.
• LT produced after December 1, 1988, by Showa Denko K.K. significantly increased the risk of EMS (OR = 25.8).
• Increased LT dosage, older age, and using LT as a sleep aid were associated with higher EMS risk.

Conclusions:

• Epidemiological data strongly support the hypothesis that a contaminant introduced during LT production by Showa Denko K.K. is the causative agent of EMS.
• This finding highlights the critical importance of rigorous quality control in supplement manufacturing to prevent toxic exposures.