If you think your daily doses of espresso or Earl Grey sharpen your mind, you just might be right, new science suggests.

如果你觉得每天喝几杯意式浓缩咖啡或伯爵茶能让头脑更清醒，最新科学研究表明你的感觉或许是对的。

A large new study provides evidence of cognitive benefits from coffee and tea — if it’s caffeinated and consumed in moderation: two to three cups of coffee or one to two cups of tea daily.

一项新的大型研究证实，咖啡和茶确实具有认知益处——前提是饮品含有咖啡因，且摄入适量：每日两至三杯咖啡或一至两杯茶。

People who drank that amount for decades had lower chances of developing dementia than people who drank little or no caffeine, the researchers reported. They followed 131,821 participants for up to 43 years.

研究人员对131821名参与者进行了长达43年的追踪，研究报告称，数十年保持这一饮用量的人群，患失智症的概率远低于很少或不摄入咖啡因的人。

“This is a very large, rigorous study conducted long term among men and women that shows that drinking two or three cups of coffee per day is associated with reduced risk of dementia,” said Aladdin Shadyab, an associate professor of public health and medicine at the University of California, San Diego, who wasn’t involved in the study.

“这项覆盖男女群体的长期大规模严谨研究表明，每天喝二到三杯咖啡，与失智症风险降低存在关联。”加州大学圣地亚哥分校公共卫生与医学副教授阿拉丁·沙迪亚布表示（他未参与此项研究）。

The findings, published Monday in JAMA, don't prove caffeine causes these beneficial effects, and it’s possible other attributes protected caffeine drinkers’ brain health. But independent experts said the study adjusted for many other factors, including health conditions, medication, diet, education, socioeconomic status, family history of dementia, body mass index, smoking and mental illness.

该研究于周一发表在《美国医学会杂志》(JAMA)，它并未证明咖啡因直接导致这些益处，也有可能是咖啡因饮品中的其他成分保护了饮用者的大脑健康。但独立专家指出，研究已对诸多其他因素做了校正，包括健康状况、用药情况、饮食、教育程度、社会经济地位、失智症家族史、体重指数、吸烟情况和精神疾病。

The caffeine correlation held regardless of whether people had genetic risk factors for Alzheimer’s or other dementias. The study, funded by the National Institutes of Health, didn’t distinguish between dementia types.

无论参与者是否携带阿尔茨海默病或其他类型失智症的遗传风险基因，咖啡因与降低失智风险的关联依然成立。这项研究由美国国立卫生研究院资助，未对失智症的具体类型做区分。

Some previous studies haven’t found cognitive benefits from caffeine, but those studies often had limitations like shorter time periods or one-time assessments of diet, experts said. The new study aligns with a growing body of research “that’s suggested caffeinated coffee may reduce risk of age-related chronic diseases,” Dr. Shadyab said.

专家表示，此前部分研究并未发现咖啡因对认知功能的益处，但这些研究往往存在局限性，比如追踪周期较短，或仅对饮食做一次性评估。沙迪亚布称，这项新研究与越来越多的研究结论一致，“均表明含咖啡因的咖啡可能降低与年龄相关的慢性疾病风险”。

Researchers followed participants in two long-running studies of medical practitioners: women in the Nurses’ Health Study and men in the Health Professionals Follow-up Study. Typically in their mid-40s or early 50s at the start, participants received repeated surveys about diet, health and lifestyle factors. During that time, 11,033 participants developed dementia, documented with death certificates or physician diagnoses.

研究人员对两项长期开展的医疗从业者研究项目进行了追踪：护士健康研究中的女性参与者，以及健康专业人员随访研究中的男性参与者。研究开始时，参与者大多在45岁左右或50岁出头，他们会多次接受饮食、健康和生活方式相关的问卷调查。在研究期间，共有11033名参与者确诊失智症，诊断依据为死亡证明或医师诊断。

Compared with people who consumed virtually no caffeine, people who drank between one and five eight-ounce cups of caffeinated coffee had about 20 percent less dementia risk. Those who drank at least one cup of caffeinated tea daily had about 15 percent less risk.

与几乎不摄入咖啡因的人相比，每天喝一到五杯（每杯约为220毫升）含咖啡因咖啡的人，失智症风险降低约20%；每天至少喝一杯含咖啡因茶的人，风险降低约15%。

But beyond two and a half cups of coffee daily, the advantage plateaued, possibly because humans cannot metabolize any more of the bioactive compounds in coffee and tea, said the study’s senior author, Dr. Daniel Wang, an epidemiologist specializing in neurodegenerative diseases at Mass General Brigham health system.

但该研究的资深作者、麻省总医院布里格姆医疗体系专攻神经退行性疾病的流行病学家丹尼尔·王表示，每天喝咖啡超过2.5杯后，益处就不再增加，原因可能是人体无法再代谢更多咖啡和茶中的生物活性化合物。

Dr. Wang, who drinks about three cups each of coffee and green tea daily, said the study didn’t find anything negative about larger caffeine quantities. But some studies suggest exceeding moderate amounts can harm health by disrupting sleep or exacerbating anxiety, said Dr. Fang Fang Zhang, an epidemiologist at Tufts University’s Friedman School of Nutrition Science and Policy, who wasn’t involved in the new research.

丹尼尔·王自己每天会喝约三杯咖啡和三杯绿茶，他称该研究并未发现大量摄入咖啡因的负面影响。但未参与此项新研究的塔夫茨大学弗里德曼营养科学与政策学院流行病学家张芳芳（音）表示，部分研究表明，过量摄入咖啡因会扰乱睡眠、加重焦虑，从而损害健康。

In a 2025 study linking caffeine consumption to lower mortality, Dr. Zhang said her team also found “you don’t get additional benefits when you go beyond three cups.” Adding more than a little milk or sugar nullified caffeine’s mortality benefits, she said. The dementia study didn’t track milk or sugar.

张芳芳表示，在2025年一项关于咖啡因摄入与降低死亡率的研究中，她的团队发现，“每天超过三杯不会获得额外益处”。她还表示，添加过多牛奶或糖，会抵消咖啡因对降低死亡率的益处，而本次失智症相关研究并未追踪牛奶和糖的添加情况。

Beyond dementia, the new study collected assessments of subjective cognitive decline — people’s perception that their memory and thinking is slipping, often an early sign on the path toward dementia. Participants who drank more caffeine were less likely to report subjective cognitive decline.

除失智症外，这项新研究还收集了主观认知衰退的评估数据——即人们感知自身记忆与思维能力下降的情况，这往往是失智症的早期信号。摄入咖啡因更多的参与者报告主观认知衰退的概率更低。

About 17,000 participants, all women over 70, also completed periodic cognitive tests. The more caffeinated participants had somewhat better scores for their age, suggesting their cognitive decline was slower by about seven months, Dr. Wang said.

约1.7万名女性参与者（均为70岁以上）还定期完成认知测试。丹尼尔·王表示，咖啡因摄入更多的人在同年龄段人群中测试成绩略好，认知衰退速度大约延缓了七个月。

Scientists say caffeine might protect brain health because it contains components that reduce neuroinflammation or aid vascular function. Research also suggests it improves insulin sensitivity, protecting against diabetes, a dementia risk factor.

科学家认为，咖啡因之所以能保护大脑健康，是因为它含有的成分可以减轻神经炎症、改善血管功能。也有研究表明，咖啡因能提高胰岛素敏感性，从而预防作为失智风险因素的糖尿病。

For people who don’t consume caffeine, Dr. Shadyab said, the findings “don’t necessarily suggest that we should be encouraging people to drink coffee, but it is reassuring to those who currently drink coffee that it may reduce risk of dementia.”

对于不喝含咖啡因饮品的人，沙迪亚布表示，研究结论“未必意味着人们应鼓励人们饮用咖啡，但对于目前有喝咖啡习惯的人来说，这一结果能让他们安心——喝咖啡或许能降低失智症风险”。

Dr. Zhang said non-caffeine drinkers might “give it a try,” starting with small amounts in case they are sensitive to caffeine.

张芳芳建议，不摄入咖啡因的人可以“尝试一下”，建议从小剂量开始，以防对咖啡因敏感。

The correlation between caffeine and lower dementia risk was strongest for people under 75. Dr. Wang said cognitive impairment develops over decades, “so if you can change your health habits early, before midlife, that will be more beneficial.”

咖啡因与降低失智风险的关联在75岁以下人群中最为显著。丹尼尔·王表示，认知障碍的形成长达数十年，“因此，如果能在中年之前尽早改变健康习惯，获益会更大”。

As medical practitioners, the participants might not reflect the general population. But Dr. Zhang noted that those who drank more caffeine were more likely to smoke and drink alcohol, suggesting they weren’t exceptionally healthier than typical Americans.

由于研究对象都是医疗从业者，这一群体可能无法代表普通人群。但张芳芳指出，咖啡因摄入更多的人吸烟、饮酒的概率更高，表明其健康状况未必优于普通美国人。

Researchers couldn’t exclude all possible influences on the results. For example, they wrote, were some people drinking decaf for medical reasons that fueled dementia, “rather than a direct beverage effect?”

研究人员无法排除所有可能影响结果的因素。他们写道，比如，是否有些人因为本身患有增加痴呆风险的健康问题才选择饮用脱因咖啡，“而非脱因咖啡直接导致风险上升”？

They also couldn’t say which might be better, brainwise: Darjeeling or matcha? Sumatra or Colombian? A $6 Americano or that cardboard-tasting free coffee from the office machine?

他们也无法判定，对大脑而言，哪种饮品更好：大吉岭茶还是抹茶？苏门答腊咖啡还是哥伦比亚咖啡？是六美元一杯的美式咖啡，还是办公室咖啡机里口感平平的免费咖啡？