The researchers sought to assess the role of various health and lifestyle factors on phenoconversion in persons who are at risk for Huntington’s disease with the CAG expansion (CAG >37). All participants were enrolled in the Prospective Huntington at Risk Observational Study. Previous research has found that the environment may cause 60% of the variance in disease onset age that is not due to CAGn, as well as an association between caffeine use and an earlier age of Huntington’s disease onset.
With the use of self-report questionnaires, the investigators analyzed participants’ exposure to tobacco, caffeine, alcohol, nonsteroidal anti-inflammatory drugs, vitamins, estrogen in women, head injury, physical activity, and cognitive activity. The researchers compared the time from baseline to motor phenoconversion between exposure groups in CAG >37 subjects by using Cox proportional hazards analyses that were adjusted for age, gender, and CAGn.
A total of 247 persons with CAG >37 completed the questionnaire. Some risk factors, such as caffeine, were “very common,” occurring in 99% of subjects, noted Dr. Tanner, who is the Director of Clinical Research at the Parkinson’s Institute and Clinical Center in Sunnyvale, California. The mean follow-up was 4.2 years (SD, 2), during which 36 persons phenoconverted.
“Drinking larger amounts of caffeinated soda predicted shorter time to phenoconversion,” said Dr. Tanner. “Six percent of low lifetime caffeinated soda consumers phenoconverted, compared with 13% of moderate consumers and 22% of high consumers.”
The hazard ratios for phenoconversion were 3.08 for moderate caffeinated soda consumers and 5.86 for high caffeinated soda consumers. Dr. Tanner noted that the association between lifetime caffeinated soda consumption and earlier onset of Huntington’s disease “was not seen with other caffeinated beverages and may be spurious. Other lifestyle risk factors associated with Parkinson’s disease or Alzheimer’s disease did not modify time to phenoconversion in Huntington’s disease.”
—Colby Stong