NEJM：多喝咖啡可能延年益寿

《新英格兰医学杂志》5月17日发表的一项研究显示，每天喝至少1杯咖啡可降低死亡风险，并且饮用量越大的人死亡风险越低。中位随访14年的结果显示，每天饮用≥6杯咖啡的男性的死亡风险比不饮用咖啡的男性低10%，每天饮用≥6杯咖啡的女性的死亡风险比不饮用咖啡的女性低15%(N. Engl. J. Med. 2012;366:1891-1904)。

这项研究由美国国家癌症研究所癌症流行病学和遗传学部的Neal D. Freedman博士及其同事进行，采用的数据来自美国国立卫生研究院-AARP饮食和健康(NIH-AARP)研究，后者旨在评价饮用咖啡与总死亡风险和原因特异性死亡风险之间的关系。NIH-AARP研究从美国6个州和2个城市纳入超过617,000例受试者(50~71岁)，并从基线(1995~1996年)随访至2008年。

Freedman博士及其同事从该研究人群中剔除罹患癌症、心脏病、卒中或咖啡饮用和吸烟信息不充分的受试者后，对229,119例男性和173,141例女性受试者进行亚组分析。共33,731例男性和18,784例女性在随访期间死亡。在男性和女性中均观察到咖啡饮用与总死亡风险之间存在轻微的负相关。

这种相关性呈剂量依赖性。与不饮用咖啡的男性相比，饮用咖啡的男性的全因死亡危险比(HR)与咖啡饮用量的对应关系：＜1杯/日，HR为0.99；1杯/日，0.94；2~3杯/日，0.90；4~5杯/日，0.88；≥6杯/日，0.90。与不饮用咖啡的女性相比，饮用咖啡的女性的HR与咖啡饮用量的对应关系：1杯/日，HR为1.01；1杯/日，0.95；2~3杯/日，0.87；4~5杯/日，0.84；≥6杯/日，0.85。

上述结果与护士健康研究(Nurses’ Health Study)和卫生专业人员随访研究(Health Professionals Follow-up Study)等大型研究观察到的结果相似。

分层分析显示，主要饮用无咖啡因咖啡的受试者的获益与主要饮用含咖啡因咖啡者的获益相似，提示咖啡中能够降低死亡风险的成分并非咖啡因，而可能是抗氧化物等其他成分。根据年龄、体重指数、有无糖尿病、是否同时饮酒，以及红肉、白肉、水果和蔬菜摄入量，是否接受激素替代治疗等因素进行亚组分析，也观察到相似结果。

在从不吸烟者(与目前吸烟者相比)和总体健康状况非常好或优的受试者(与健康差或可者相比)中观察到的咖啡饮用与总死亡风险之间的负关联最强烈。

对原因特异性死亡进行分析发现，咖啡饮用与男性和女性的绝大多数死亡原因呈负相关。咖啡饮用量越大，则死于心脏病、呼吸系统疾病、卒中、损伤和意外、糖尿病和感染的风险越低。然而，咖啡不能降低女性的癌症死亡风险，并且与男性的癌症死亡风险呈临界正相关。

研究者表示，由于这是一项观察性研究，因此不可能断定咖啡饮用与死亡风险之间的负相关是因果关系，但至少可使人们不必过分担心喝咖啡会对健康产生不良影响。

该研究获美国国立卫生研究院等机构支持。研究者声明无经济利益冲突。

拓展阅读：

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JAFC：长期饮咖啡降低糖尿病发病率

喝咖啡能降低2型糖尿病发病风险吗？

咖啡有助于预防头颈部癌

美发现咖啡降低患皮肤癌风险

Drinking at least one cup of coffee daily may be linked to reduced mortality risks, and people who consume more may enjoy even lower risks, according to a report examining coffee consumption among more than 400,000 people in the May 17 issue of the New England Journal of Medicine.

Compared with men who didn’t drink coffee, those who drank six or more cups per day had a 10% lower risk of death during a median follow-up of 14 years. Compared with women who didn’t drink coffee, those who drank six or more cups per day had a 15% lower risk, reported Neal D. Freedman, Ph.D., of the U.S. National Cancer Institute’s Division of Cancer Epidemiology and Genetics, and his associates.

The benefit of coffee consumption was similar between people who predominantly drank decaffeinated and those who predominantly drank caffeinated coffee, so caffeine does not appear to be the component of the beverage that improves mortality, they said.

In previous studies, coffee drinking has been linked to lower rates of diabetes, inflammatory diseases, and stroke. But studies examining a link with heart disease have produced mixed results, and “associations with cancer have generally been null,” the researchers noted. Thus, coffee’s association with total mortality has been mixed.

Dr. Freedman and his colleagues used data from the U.S. National Institutes of Health–AARP Diet and Health Study to assess the relationship between coffee drinking and both total and cause-specific mortality. The NIH-AARP study involved more than 617,000 subjects aged 50-71 years who were followed from baseline (1995-1996) through 2008, so it had ample power to detect even modest associations, the investigators noted.

For the Diet and Health Study, subjects residing in six states and two cities answered a comprehensive questionnaire about diet and lifestyle at baseline. Dr. Freedman and his associates assessed a subgroup of 229,119 men and 173,141 women from this study population, after excluding those with cancer, heart disease, stroke, or inadequate information on coffee drinking and cigarette smoking.

A total of 33,731 men and 18,784 women died during follow-up. The researchers found a modest inverse association between coffee drinking and total mortality for both sexes (N. Engl. J. Med. 2012;366:1891-1904).

This association was dose dependent. Hazard ratios for death from any cause among men who drank coffee, compared with men who did not, were 0.99 for less than one cup per day, 0.94 for one cup, 0.90 for two to three cups, 0.88 for four to five cups, and 0.90 for six or more cups.

Hazard ratios among women who drank coffee, compared with women who did not, were 1.01 for less than one cup per day, 0.95 for one cup, 0.87 for two to three cups, 0.84 for four to five cups, and 0.85 for six or more cups.

These hazard ratios are similar to those found in several larger, more recent studies, including the Nurses’ Health Study and the Health Professionals Follow-up Study, the investigators said.

In an analysis of the data stratified by the predominant type of coffee consumed, the link between intake and mortality was similar for caffeinated and decaffeinated coffee. This suggests that the mortality benefit is due to some compound contained in coffee other than caffeine, such as antioxidants.

The association also persisted across numerous subgroups of study participants, regardless of age; body mass index; the presence or absence of diabetes; concomitant alcohol consumption; high or low intake of red meat, white meat, fruit, and vegetables; and use or nonuse of hormone replacement therapy.

The strongest inverse associations between coffee drinking and total mortality were found among people who had never smoked (compared with current smokers) and those who reported having very good to excellent overall health (compared with poor to fair health).

When cause-specific mortality was examined, coffee intake was inversely related to most major causes of death in both men and women. Higher coffee consumption was linked to lower mortality due to heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections.

However, coffee did not protect against cancer mortality in women, and it showed a borderline positive association with cancer mortality in men.

“Given the observational nature of our study, it is not possible to conclude that the inverse relationship between coffee consumption and mortality reflects cause and effect,” the investigators said.

Nevertheless, “our results provide reassurance with respect to the concern that coffee drinking might adversely affect health.”

This study was supported by the U.S. National Institutes of Health, the U.S. National Cancer Institute, and the NCI’s Division of Cancer Epidemiology and Genetics. No financial conflicts of interest were reported.