The author: Professor Yasser Metwally
INTRODUCTION
September 4, 2008 — A new analysis combining the Health Professionals Follow-Up Study (HPFS) and the Nurses’ Health Study (NHS) confirms that in addition to preventing chronic diseases such as diabetes and coronary heart disease, an overall healthy lifestyle is associated with a significantly decreased risk for stroke.
The reduction in stroke risk was driven by a reduction in ischemic rather than hemorrhagic stroke. A healthy lifestyle combining not smoking, a healthy weight, a healthful diet including moderate alcohol consumption, and daily exercise reduced ischemic strokes by approximately half in both men and women.
“This study further supports the beneficial impact of a low-risk lifestyle on the primary prevention of chronic disease and long-term well-being,” the researchers with first author Stephanie E. Chiuve, ScD, from the Harvard School of Public Health in Boston, Massachusetts, conclude.
Their report is published in the August 11 Online First issue of Circulation.
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Combination of Risks
Previous research from the Harvard group has suggested that the combination of a healthful diet, exercise, not smoking, and maintaining an optimal body weight may be more effective than any 1 of these factors alone in preventing cardiovascular disease, diabetes, and cancer. In this analysis, they used the large datasets of the NHS (including 71,243 women) and the HPFS (including 43,685 men), both prospective cohort studies, to see whether this was also true for stroke, where the risk factors may be somewhat different than for these other conditions.
At baseline, all participants were free of cardiovascular disease and cancer and provided dietary data, updated every 4 years, and information on lifestyle habits and medical history, updated biennially. A low-risk lifestyle was defined as not smoking, a body mass index (BMI) of less than 25 kg/m2, 30 minutes or more per day of moderate physical activity, modest alcohol consumption of 5 to 30 g/day for men and 5 to 15 g/day for women, and scoring within the top 40% of a healthy diet score.
During follow up, there were 1559 strokes (853 ischemic, 278 hemorrhagic, 428 unknown type) in the women in NHS and 994 strokes (600 ischemic and 161 hemorrhagic, 233 unknown type) in the men in the HPFS.
The researchers report that women with all 5 of these low-risk factors had a significantly reduced risk for both total stroke and ischemic stroke of approximately 80% vs those with none of these factors. For the men, there was a 69% reduced risk for total stroke and an 80% reduced risk for ischemic stroke.
Table 1. Relative Risk for Stroke Associated With Adherence to 5 Healthy Lifestyle Factors vs No FactorsEndpoint Men Women
| Endpoint |
Men |
Women |
| Total stroke |
0.31 (0.19 – 0.53) |
0.21 (0.12 – 0.36) |
| Ischemic stroke |
0.20 (0.10 – 0.42) |
0.19 (0.09 – 0.40) |
Table 2. Proportion of Strokes Attributable to Lack of Adherence to a Low-Risk Lifestyle (Population-Attributable Risk [PAR] %)Endpoint Men Women
| Endpoint |
Men |
Women |
| Total stroke (%) |
35 (7 – 58) |
47 (18 – 69) |
| Ischemic stroke (%) |
52 (19 – 75) |
54 (15 – 78) |
“This study shows that following a health lifestyle, which has been associated with up to 80% lower risk of coronary heart disease and 90% lower risk of diabetes, may also prevent more than half of ischemic strokes,” Dr. Chiuve said in a press release from the American Heart Association.
The study is observational, and the habits were self-reported, the study authors caution. However, they note, “the PAR% most likely underestimates the burden of unhealthy behavior on risk of stroke in the general population because the prevalence of these low-risk factors and, more important, the prevalence of extreme levels of unhealthy behaviors are greater in the US population than in our cohorts.
“Greater benefit is likely to be gained by adherence to healthy lifestyle choices in populations with less healthy lifestyle than in these populations of health professionals,” they conclude.
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Clinical Context
Stroke is the third leading cause of death in the United States. Nonfatal stroke is a leading cause of permanent disability, and an overall healthy lifestyle has been linked to a lower incidence of cardiovascular disease in general.
This is an examination of longitudinal cohort data on women in the NHS and men in the HPFS to examine the risk reduction for stroke associated with adoption of healthy lifestyle habits.
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Study Highlights
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The NHS (71,243 women) was established in 1976 and the HPFS (43,685 men) in 1986, both consisting of mainly white women and men without cardiovascular disease at baseline.
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Dietary information was collected every 4 years, and baseline data included demographics and medical history.
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Biennial information was collected on smoking, weight, clinician diagnosis of hypertension, dyslipidemia, diabetes, and medication use.
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In women, menopausal status and use of hormones were also elicited.
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Physical activity was determined as average hours per week spent in moderate to vigorous activities.
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A validated food frequency questionnaire was used to determine food intake and nutrient composition.
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A summary score was created with use of the Alternate Healthy Eating Index consisting of 8 of 9 components such as vegetable and fruit intake and ratio of chicken to red meat.
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Additional dietary scores were assigned according to low sodium intake and the 6-nutrient diet score.
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5 lifestyle factors were examined: smoking, exercise, diet, BMI, and alcohol consumption on the basis of the strength of evidence from cardiovascular disease prevention.
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For each variable, a score of 1 was assigned if the participant met the criterion and 0 if not.
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A higher score represented a healthier lifestyle.
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Primary outcome was confirmed stroke as defined by the National Survey of Stroke criteria, requiring sudden onset of neurologic deficit lasting 24 hours or longer or until death.
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Medical records were reviewed to confirm the diagnosis; for those who died, the family was contacted and diagnosis confirmed by the National Death Index or medical records.
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Stroke was classified as ischemic, hemorrhagic, and unknown type.
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During follow-up, there were 1559 cases of stroke in the NHS (853 ischemic, 278 hemorrhagic, 428 unknown type) and 994 in the HPFS (600 ischemic, 161 hemorrhagic, 233 unknown type).
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In women and men, smoking, exercise, diet, and BMI were directly associated with stroke risk.
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Alcohol had a J-shaped association, with light to moderate consumption being protective and high risk in heavy drinkers (= 30 g daily).
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Lower scores on the 3 dietary scores were associated with a higher risk for stroke.
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Midlife BMI was more strongly associated with stroke than most recent BMI.
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Risk for hemorrhagic stroke followed ischemic stroke, but the associations were less strong.
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Not smoking, optimal BMI, daily exercise, and moderate alcohol consumption were independent predictors of total stroke in women.
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Both men and women adherent to all 5 healthy lifestyle patterns had an 80% reduced risk for stroke.
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For women adherent to all 5 lifestyle habits, the relative risks were 0.21 for total stroke and 0.19 for ischemic stroke.
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For men, the relative risks were 0.31 for total stroke and 0.20 for ischemic stroke.
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In women, 47% of total strokes and 54% of ischemic strokes were attributable to not following a healthy lifestyle.
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In men, the percentages were 35% of total strokes and 52% of ischemic strokes.
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In the NHS, 70% of total cardiovascular disease, 80% of coronary heart disease, and 90% of diabetes were attributed to not following a healthy lifestyle.
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In the HPFS, 62% of coronary heart disease and 79% of coronary heart disease in men younger than 65 years were attributed to not following a healthy lifestyle.
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In men and women 70 years or older, 61% of cardiovascular deaths could have been avoided through a healthy lifestyle.
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Pearls for Practice
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Healthy lifestyle habits include not smoking, maintenance of optimal BMI, moderate alcohol consumption, and daily exercise.
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In men and women, maintenance of healthy lifestyle habits is associated with an 80% reduction in the risk for stroke.
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References
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Circulation. Published online August 11, 2008.
