Caffeine Consumption in First-Degree Relatives of Essential Tremor Cases: Evidence of Dietary Modification before Disease Onset

Background: Caffeine can exacerbate tremor. Reducing caffeine intake or switching to decaffeinated beverages can lessen tremor. Unaffected relatives of essential tremor (ET) cases often have mild, subclinical tremor. One question is whether the coffee and tea consumption pattern in these individuals differs from that of controls (Co). Methods: We ascertained the patterns of coffee and tea intake using a structured questionnaire, and compared the use in unaffected first-degree relatives of ET cases (FD-ET) to the use in age-matched Co. Three measures of relative caffeinated coffee + tea to decaffeinated coffee + tea were constructed. Caffeine index 1 = (cups of caffeinated coffee + tea) - (cups of decaffeinated coffee + tea) consumed on the day of evaluation. Caffeine index 2 = (cups of caffeinated coffee + tea) - (cups of decaffeinated coffee + tea) consumed in a typical month. The percentage of coffee and tea that was caffeinated in a typical month was also calculated. Results: There were 263 individuals (190 FD-ET, 73 Co). Caffeine index 1 in FD-ET was less than 1-half that of Co (p = 0.001). Caffeine index 2 was similarly lower in FD-ET than Co (p = 0.027). The percentage of coffee and tea that was caffeinated in a typical month was also significantly lower in FD-ET than Co (p = 0.018). Conclusion: The balance of caffeinated to decaffeinated beverages is different in FD-ET than Co. These data raise several intriguing questions. Among these is whether relatives of ET cases modify their caffeine consumption before disease onset.