A study found that daily drinking of tea (either black tea/oolong or green tea) is associated with a lower risk of "neurocognitive disorders" - in cognitive impairment in women, and in a lower risk of Alzheimer's disease in both men and women who are genetically predisposed to the disease (apolipoprotein E (APOE) genotype) - when compared to those who never or rarely drank tea. The researchers called long-term daily tea drinking as "neuroprotective".
The study followed 957 residents of Singapore for several years. All were "cognitively normal" when the study started (average age 64 1/2 years), but 72 people or 7.5% had developed neurocognitive disorders by the second follow-up (after 4 years). The study found that there was a dose-dependent relationship - the more tea that was drunk daily, the more protective it appeared to be. And it was most protective in those who consistently drank tea at both time points - when the study started and till the end. However, there was a gender difference - it seemed to protect women from neurocognitive disorders, but not men. But in those who were genetically predisposed to Alzheimer's - tea drinking was protective for both males and females. Further studies will follow up to see if the gender difference holds - they couldn't explain it.
The researchers also point out that tea drinking has a long history in Chinese culture as an natural "attention enhancer" and strong tea is drunk as to maintain alertness and concentration. Sounds a lot like why people drink coffee. From Medical Xpress:
Tea drinking reduces the risk of cognitive impairment in older persons by 50 per cent and as much as 86 per cent for those who are genetically at risk of Alzheimer's. A cup of tea a day can keep dementia away, and this is especially so for those who are genetically predisposed to the debilitating disease, according to a recent study led by Assistant Professor Feng Lei from the Department of Psychological Medicine at National University of Singapore's (NUS) Yong Loo Lin School of Medicine. The longitudinal study involving 957 Chinese seniors aged 55 years or older has found that regular consumption of tea lowers the risk of cognitive decline in the elderly by 50 per cent, while APOE e4 gene carriers who are genetically at risk of developing Alzheimer's disease may experience a reduction in cognitive impairment risk by as much as 86 per cent.
He added, "Based on current knowledge, this long term benefit of tea consumption is due to the bioactive compounds in tea leaves, such as catechins, theaflavins, thearubigins and L-theanine. These compounds exhibit anti-inflammatory and antioxidant potential and other bioactive properties that may protect the brain from vascular damage and neurodegeneration. Our understanding of the detailed biological mechanisms is still very limited so we do need more research to find out definitive answers.