Caffeine, postmenopausal estrogen, and risk of Parkinson’s disease
Ascherio, A.. Chen H, Schwarzschild MA, Zhang SM, Colditz GA, Speizer FE. (2003) Caffeine, postmenopausal estrogen, and risk of Parkinson’s disease , 2003 Mar 11;60(5):790-5
This article is part of a longitudinal study that looked at the effects of caffeine and estrogen use in postmenopausal women. The original cohort included 121,700 registered nurses in 11 states and was followed from 1976 until the data was analyzed in 1998 (the data continues to be collected). They found that 154 women were diagnosed with PD. There were multiple results from this study and only a few of those will be discussed here. The incidence of PD was not significantly associated with hormone use, regardless of type or duration of the use. They found, however, that the consumption of caffeine coupled with use of postmenopausal hormones did relate to the incidence of PD. Specifically, the use of postmenopausal hormones in women with a low caffeine intake (approximately _ cup of coffee/day) had a lower incidence of PD. The opposite was true for women that used postmenopausal hormones and had high caffeine intake (approximately 5 cups of coffee/day); the incidence of PD was higher. It was suggested that exogenous (created outside of the body and ingested) estrogen blocks the metabolism of caffeine. These authors stated that estrogen could possibly be neuroprotective, as supported by animal studies, but it still remains unclear what fully explains why women have a lower risk of PD than men. They also suggested that caffeine and estrogen use needs to be further evaluated in future studies of PD. It is notable that other findings were reported in this study, but explanations for them were not included. Additionally, there appear to be many factors whose interactions may be related to PD. In this particular study, there may be some other variables influencing the onset of PD that the authors did not take into account.