【美联社奥兰多11月16日电】血型可能影响患中风风险的大小。一项研究结果发现，与O型血———系最常见血型———的人相比，AB型血的人和B型血的女性患中风的可能性会略大些。
此项科研与其他类似研究的结果相符，如A、B和AB型血的人在腿部出现血块以及患心脏病的几率更大。O型血的人出现流血的几率更高，也就意味着出现血块的几率较低，而血块是导致中风的主要原因。
该科研项目负责人、哈佛大学布里格姆妇科医院预防医学首席研究员琼·曼森博士说：“目前有越来越多的迹象表明，血型或许会影响患慢性病风险的大小。”
曼森说：“目前还没有到我们希望提醒人们并作出相关解释的地步。但血型也是人们希望去了解的一种风险。”她说，这会让人们更有理由去控制好血压和胆固醇了。
美国心脏病协会周三在一次会议上公布了这项研究结果。共有9万名男性和女性参与了这项科研活动，其中包括两项观察性健康研究，时间跨度超过了20年。
科研人员研究了2901例中风病例，并考虑了其他可能导致中风的因素，如高血压。科研人员而后发现：与O型血的人相比，AB型血的人患中风几率要高26%，B型血的女性患中风几率要高15%。
人体血型取决于红细胞表面的蛋白质特性。人体在生命早期会根据蛋白质的特性形成免疫系统反应模式。曼森说，某些特定血型可能增加红细胞形成凝块并粘着在血管壁上的几率，那样就会为形成血块创造条件。
杜克大学中风研究中心主任拉里·戈尔茨坦说：“你不可能改变血型。我们也不知道，实际造成中风风险的是血型本身还是与血型相配的其他什么基因。”
他还说，引发中风风险的原因很多，其他一些原因比血型更重要，如吸烟、过量饮酒和缺乏锻炼等。
ORLANDO -- The conventional stroke risks such as hypertension and smoking are well known, but researchers have now found that blood type, particularly the ABO blood group, is also related to the risk of stroke.
In two cohorts with more than two million person-years of follow-up, men and women in the AB blood group were very significantly associated with a 26% increase for the risk of developing stroke compared with those with type O blood (95% CI 1.11 to 1.44), Lu Qi, MD, PhD, from Harvard School of Public Health, and colleagues found.
Compared with women with type O blood, women with type B had a marginally significant 15% higher risk of stroke, according to the study presented at the American Heart Association meeting here.
Qi is unsure of the mechanism behind the conferred higher risk of stroke with various blood types. However, previous genetic studies have shown that blood types AB and B are associated with cardiovascular risk factors, such as endothelial dysfunction leading to coronary heart disease.
Other studies have shown an association between type A and increased LDL cholesterol levels and type B with increased cholesterol and systolic blood pressure. But no studies have shown blood type to be associated with stroke risk, Qi told MedPage Today.
For this study, researchers analyzed data from two prospective longitudinal cohorts with 26 and 20 years of follow-up. The Nurses' Health Study (NHS) includes 61,973 women and the Health Professionals Follow-up Study (HPFS) includes 27,808 men.
Information on ABO blood group was self-reported, but has been shown to have a high degree of external validity, Qi said.
Data were adjusted for age, smoking, body mass index (BMI), alcohol intake, physical activity, aspirin use, ethnicity, family history of coronary heart disease, history of hypertension and high cholesterol and type 2 diabetes, menopausal status, and postmenopausal hormone use.
At least 93% of participants in each blood type group (O, A, B, AB) were white. In both cohorts, the number of participants was greatest in O, followed by A, B, and then AB, which is consistent with the overall population, Qi said.
Baseline characteristics were similar in each cohort, with an average age of 46 for women and 53 for men, and average BMIs of 24 and 25 kg/m2 for women and men, respectively.
The average percentage of the history of disease in women and men, respectively, was as follows:
- Hypertension -- 15% and 22%
- High cholesterol -- 4.8% and 10.9%
- Type 2 diabetes -- 1.6% and 2.4%
- Family history of coronary heart disease -- 13% for both
In the NHS group, there was a total of 1,995 participants who developed stroke, while in the HPFS group, 906 participants developed stroke.
Although women with type B had a 15% increase in stroke risk (RR 1.15, 95% CI 1.00 to 1.32), no such risk appeared in the male cohort (RR 0.84, 95% CI 0.68 to 1.08).
"In fact, in men, the association between type B was not significant, and the stroke risk appears to go in the opposite direction. It looks like there is a decrease in risk," Qi said.
Both of these results "surprised" researchers. Qi said the increased risk for women could be due to the larger sample size compared with men or to chance. The decreased risk in men was also surprising because, in other studies, men with type B blood were associated with increased coronary heart disease and myocardial infarction.
"It's difficult to believe this blood group has a lower risk of stroke," he said.
In the combined multivariate analysis, the risk of ischemic stroke in group AB was greater than for hemorrhagic stroke compared with group O (RR 1.30, 95% CI 1.12 to 1.50 versus RR 1.20, 95% CI 0.79 to 1.82).
The study was limited by the population being mostly white, and it was underpowered to detect the associations with the subtypes of stroke such as hemorrhagic.
Qi said the next step is to determine whether lifestyle factors impact the stroke risk conferred by blood type.
http://www.medpagetoday.com/MeetingCoverage/AHA/29804
