【美聯社奧蘭多11月16日電】血型可能影響患中風風險的大小。一項研究結果發現，與O型血———係最常見血型———的人相比，AB型血的人和B型血的女性患中風的可能性會略大些。
此項科研與其他類似研究的結果相符，如A、B和AB型血的人在腿部出現血塊以及患心髒病的幾率更大。O型血的人出現流血的幾率更高，也就意味著出現血塊的幾率較低，而血塊是導致中風的主要原因。
該科研項目負責人、哈佛大學布裏格姆婦科醫院預防醫學首席研究員瓊·曼森博士說：“目前有越來越多的跡象表明，血型或許會影響患慢性病風險的大小。”
曼森說：“目前還沒有到我們希望提醒人們並作出相關解釋的地步。但血型也是人們希望去了解的一種風險。”她說，這會讓人們更有理由去控製好血壓和膽固醇了。
美國心髒病協會周三在一次會議上公布了這項研究結果。共有9萬名男性和女性參與了這項科研活動，其中包括兩項觀察性健康研究，時間跨度超過了20年。
科研人員研究了2901例中風病例，並考慮了其他可能導致中風的因素，如高血壓。科研人員而後發現：與O型血的人相比，AB型血的人患中風幾率要高26%，B型血的女性患中風幾率要高15%。
人體血型取決於紅細胞表麵的蛋白質特性。人體在生命早期會根據蛋白質的特性形成免疫係統反應模式。曼森說，某些特定血型可能增加紅細胞形成凝塊並粘著在血管壁上的幾率，那樣就會為形成血塊創造條件。
杜克大學中風研究中心主任拉裏·戈爾茨坦說：“你不可能改變血型。我們也不知道，實際造成中風風險的是血型本身還是與血型相配的其他什麽基因。”
他還說，引發中風風險的原因很多，其他一些原因比血型更重要，如吸煙、過量飲酒和缺乏鍛煉等。
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
