作者：Allison Gandey
出處：WebMD醫學新聞
February 5, 2010 — 研究者們報告，相較於北美洲長期居民，新移民過早發生急性中風的機率較低。在校正多重危險因子後，相對風險大約低了30%。
由多倫多大學中風預後研究加拿大工作小組Gustavo Saposnik醫師領導的團隊表示，我們核對中風風險是否存在著健康新移民的效應。當我們繼續專注在降低所有成人中風風險時，針對保留新移民健康狀態的政策是有必要的。
這項試驗稱為PRESARIO或最近移民至安大略相關過早中風風險（Risk of Premature Stroke Associated with Recency of Immigration to Ontario）研究，是一項以群眾為基礎、相對應的回溯性世代研究。
這項研究結果發表於2月9日的神經學期刊，先前已經在線上發表。
在隨後的主編評論中，來自俄亥俄州代頓市Wright州立大學的Brady Jacobs醫師稱這項研究是令人信服的。對於新移民進行的流行病學研究，在釐清一般大眾罹患該疾病原因與相關因子不是那麼顯而易見時是有潛力的。
【缺血性中風與出血性中風風險相當】
研究收納在安大略健康保險計畫的受試者們，這項計畫涵蓋大部分無使用者費用健康照護。
加拿大的新移民率是世界上數一數二的。根據2006年時進行的人口普查，安大略28%群眾是外來居民，在加拿大所有省份中是最高的。
研究者們比對超過960,000位新移民以及超過3,200,000長期居民的出生年、性別與居住地。新移民以新接受全民公共衛生保險納保認定，而長期居民定義為納保超過5年以上。
這項研究受試者們的平均年齡約為34歲，在平均追蹤大約6年後，觀察到中風的整體數目為6216件。
Saposnik醫師與他的團隊發現，新的加拿大移民比較不會中風。研究者們觀察到缺血與出血事件風險估計相當。
表一、急性中風發生率
群眾 | 每年每一萬人發生率 |
新移民 | 1.69 |
長期居民 | 2.56 |
危險比值為0.66，95%信賴區間為0.62-0.71。在校正年齡、收入四分位數、城市與郊區居民、高血壓病史、糖尿病、吸菸，還有健康保險聲明後，中風危險比值為0.69，95%信賴區間為0.64-0.74。
研究者們報告，雖然新加拿大移民中風機率仍然較低，但是一旦中風，住院天數較長，且轉介到長期照護機構的可能性較高。
研究者們表示，他們的研究有幾項限制。舉例來說，他們並沒有辦法取得研究受試者們的教育程度或是生活型態，他們也沒有測量血壓、血糖、血脂肪或是中風嚴重度。
顯然地，研究作者們寫到，有新移民出生國詳細資料以及許多基本生理與社會指標可以協助解釋為什麼他們罹患中風機率比長期居民低，一旦罹患中風，病情卻更加嚴重。
研究者們指出，新移民到北美洲的人們年齡大都小於50歲，且心血管疾病風險比較少。除此之外，可以想見的，再移民的壓力可能讓他們處於中風高風險。
而這在目前的群眾卻非如此。研究作者們承認許多問題仍然存在。
Jacobs醫師附帶表示，或許基因、飲食、天氣、感染或是沒有感染特定病原菌可能協助維持移民後較低的中風風險。
試驗作者們表示，我們學到可以轉換成整個族群長期的健康好處，不論他們的居住狀態。
共同作者Eva Lonn接受阿斯特捷利康藥廠、葛蘭素史克、默克、諾華、賽諾菲安萬特與亞培藥廠贊助。她接受來自羅氏、加拿大衛生研究機構以及加拿大心臟與中風基金會的研究經費。
New Immigrants Have Lower Acute Stroke Risk
By Allison Gandey
Medscape Medical News
February 5, 2010 — Recent immigrants are less likely to have premature acute stroke than long-term residents of North America, a new study shows. The approximately 30% lower relative risk held even after adjusting for multiple risk factors, report researchers.
"Our findings verify the presence of a healthy immigrant effect in relation to stroke risk," note the group led by Gustavo Saposnik, MD, from the Stroke Outcome Research Canada Working Group at the University of Toronto. "Policies are needed that aim to preserve the healthier state of new immigrants, while continuing to focus on lowering stroke risk among all adults."
The study known as PRESARIO or Risk of Premature Stroke Associated with Recency of Immigration to Ontario was a population-based, matched, retrospective cohort study.
Results are published in the February 9 issue of Neurology and were released early online.
In an accompanying editorial, Bradley Jacobs, MD, from Wright State University in Dayton, Ohio, called the work compelling. "The epidemiologic study of disease in immigrants holds promise for elucidating causes of and contributors to disease not readily evident in a general population," he noted.
Similar Risk for Ischemic and Hemorrhagic Strokes
Study participants were enrolled in the Ontario Health Insurance Plan, which covers most aspects of health care with no user fee.
Canada has one of the highest rates of immigration in the world. According to the 2006 Census, 28% of the total population of Ontario is foreign born — this is the highest rate among all Canadian provinces.
Investigators matched more than 960,000 new immigrants to more than 3,200,000 long-term residents by year of birth, sex, and location. Immigrants were identified as new recipients of universally available public health insurance, and long-term residents were those insured for 5 years or longer.
The mean age of the study participants was about 34 years, and the total number of observed strokes was 6216 after a median duration of follow-up of about 6 years.
Dr. Saposnik and his team found that new Canadians were less likely to have a stroke. Investigators observed similar risk estimates for both ischemic and hemorrhagic events.
Table 1. Incidence of Acute Stroke
| Population | Rate Per 10,000 Person-Years |
| Immigrants | 1.69 |
| Long-term residents | 2.56 |
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The hazard ratio was 0.66, with a 95% confidence interval of 0.62 to 0.71. After adjusting for age, income quintile, urban vs rural residence, history of hypertension, diabetes mellitus, and smoking, and number of health insurance claims, the hazard ratio for stroke was 0.69, with a 95% confidence interval of 0.64 to 0.74.
Investigators report that although new Canadians sustained fewer strokes, those who did have one had slightly longer hospital stays and a marginally higher likelihood of transfer to a long-term care facility.
The researchers note a number of limitations to their study. For example, they did not have access to information on the study participants' educational level or lifestyle. They also did not have measures of blood pressure, blood glucose, serum lipids, or stroke severity.
Clearly, the study authors write, having detailed information of the country of birth and some basic physical and social measures of new immigrants could help explain why they have fewer strokes than long-term residents but may do worse after having a stroke.
The researchers point out that new immigrants to North America are typically younger than 50 years and have fewer risk factors for cardiovascular disease. Still, they note, the stress of resettlement could conceivably place them at higher risk for stroke.
This was not the case in the current population. The study authors acknowledge that many questions remain.
"Perhaps genetics, diet, weather, infection, or lack of infection may help to maintain a lower risk of stroke after immigration," Dr. Jacobs added.
"What we learn," the study authors note, "could translate into long-term health benefits for the whole population, irrespective of their immigrant status."
Coauthor Dr. Eva Lonn has received funding from AstraZeneca, GlaxoSmithKline, Merck Serono, Novartis, Sanofi-Aventis, and Abbott. She receives research support from Roche, the Canadian Institutes of Health Research, and the Heart and Stroke Foundation of Canada.
Neurology. 2010;74:451-457.
