锻炼频率关乎卒中风险 至少对男性而言

在美国南方“卒中带”开展的一项以人群为基础的大规模纵向研究显示，每周进行至少4次引起出汗的锻炼，或许有预防卒中的作用(Stroke 2013 July 18 [doi:10.1161/STROKEAHA.113.001538])。

这项研究是由南澳大利亚大学的Michelle N. McDonnell博士及其同事开展的，它证实了既往有关锻炼对卒中风险影响的报告结果，但同时也首次表明，锻炼对卒中风险的剂量依赖性效应仅存在于男性中，而在女性中未观察到该现象。每周锻炼至少4次，强度达到引起出汗的男性，其卒中风险显著低于每周只锻炼1~3次的男性。而女性不论锻炼到何种程度，其卒中风险相对于不锻炼的女性均无显著降低。



卒中的地域与种族差异的原因(REGARDS)研究纳入了27,348例年龄≥45岁的受试者，根据受试者自我报告的中至高强度身体锻炼的频率，将其分为三类：从不锻炼，每周锻炼1~3次，以及每周锻炼4次或以上。根据是否引起出汗来判断身体活动性。

研究者通过电话获取了受试者的人口统计学信息和病史，并通过亲自随访面谈了解受试者的躯体指标。研究者每6个月进行1次随访面谈，采集人口统计学、社会经济因素、卒中危险因素(包括体重指数、吸烟状态、饮酒、糖尿病和高血压)以及躯体健康局限性，以评估潜在的卒中风险，平均随访5.7年。

在随访期间共发生了918例得到证实的卒中/短暂性脑缺血发作，后者与身体活动性有明显关联。身体活动性最强的受试者具有较低的体重指数、较少罹患糖尿病，而且男性、白人和教育程度/收入较高者占更大比例。在校正年龄、性别、种族、地域、居住在城市/农村以及社会经济状态等因素后，自称身体活动性很低的受试者的卒中风险，比每周至少锻炼4次者高出20%[危险比(HR)，1.20；95%置信区间(CI)：1.01~1.42]。

从不锻炼的受试者与每周锻炼1~3次者相比，HR为1.16，但未达到统计学显著性，并且在额外校正地域、居住在城市/农村以及社会经济状态等因素后，二者的差异进一步降低。

每周锻炼至少4次对于缺血性和出血性卒中具有相似的保护作用。

在将卒中危险因素加入统计模型后，研究者发现每周锻炼至少4次的保护效应有所减弱，不再具有统计学显著性。由于中至大量饮酒者在规律锻炼的受试者中占有较高比例，因此研究者猜测“锻炼在降低卒中风险方面的获益，可能原因主要在于身体活动对于体重指数、高血压和糖尿病的积极影响，尽管身体活动也可能通过其他的生物学作用(例如改善内皮功能和降低血小板活性)降低卒中风险”。

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By: MADHU RAJARAMAN, Cardiology News Digital Network

Exercising to the point of inducing a sweat at least four times per week may have a protective effect against stroke, according to the results of a large, population-based, longitudinal study of people in the "Stroke Belt" of the Southern United States.

The study, conducted by Michelle N. McDonnell, Ph.D., of the University of South Australia, Adelaide, and her colleagues, confirms previous reports about the effect of exercise on stroke risk, but it is the first to find a dose-response effect of exercise on stroke risk only in men and not in women. Men who exercised to the point of sweating at least four times per week had a significantly lower risk of stroke than did men who exercised one to three times per week. However, women who exercised at either level of frequency did not have a significantly lower risk of stroke, compared with women who did not exercise (Stroke 2013 July 18 [doi:10.1161/STROKEAHA.113.001538]).

The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study assessed 27,348 participants aged 45 years or older who self-reported their frequency of moderate to vigorous physical activity within three categories: none, one to three times per week, and four or more times per week. Intensity of physical activity was determined by whether the exercise induced sweat in participants.

The researchers obtained demographic information and medical history via telephone, and conducted in-person follow-up interviews to take participants’ physical measurements. They conducted follow-up interviews with participants every 6 months to assess for potential stroke risk for a mean of 5.7 years, collecting data on demographics, socioeconomic factors, stroke risk factors (including mass index, smoking status, alcohol use, diabetes, and hypertension), and physical health limitations.

A total of 918 confirmed stroke/transient ischemic attack cases occurred over the follow-up period, with a significant association between activity and stroke. The most physically active participants had a lower body mass index and prevalence of diabetes and were male, white, and highly educated with high incomes. Participants who reported no physical activity had a 20% greater risk for stroke than did participants who exercised at least four times per week (hazard ratio = 1.20; 95% confidence interval, 1.01-1.42), after adjustment for age, sex, race, and age-race interaction. This remained the same after further adjustments were made for region, urban/rural residence, and socioeconomic status.

The hazard ratio was 1.16 for individuals who did not exercise, compared with those who did so one to three times per week, but it was not statistically significant and was further reduced when additional adjustments were made for region, urban/rural residence, and socioeconomic status.

Exercising at least four times per week was similarly protective against both ischemic and hemorrhagic stroke.

A statistical model in the study that added stroke risk factors attenuated the effects of exercising at least four times per week to the point where it was no longer significant. Individuals who regularly participated in physical activity were more likely to be moderate or heavy consumers of alcohol, leading the investigators to suggest that exercise’s benefit on reducing stroke risk "is likely to be explained for the most part by the positive effect that physical activity has on body mass index, hypertension, and diabetes mellitus, although physical activity also has the potential to reduce stroke risk because of other biological actions (e.g., improving endothelial function and reducing platelet activity)," the investigators wrote.