Research Review by Dr. Shawn Thistle©
Study Title:Healthy lifestyle and the risk of stroke in women
Authors:Kurth T et al.
Publication Information:Archives of Internal Medicine 2006; 166: 1403-1409.
Summary:It has been well established that a healthy lifestyle is associated with a decreased risk of heart disease, diabetes, and obesity (among other things). The association of modifiable lifestyle factors to stroke however, is not as clear.
This prospective cohort study began in 1993, and followed almost 40 000 female healthcare professionals (> 45 years of age at study inception) for over 10 years. From this study, a wealth of data emerged regarding the association of lifestyle factors with various diseases and medical outcomes.
The focus of this study was to illuminate the impact of modifiable lifestyle factors on the incidence of stroke.
All data were collected by postal questionnaire at regular intervals throughout the study. Lifestyle factors (described below) were statistically analyzed for their association with stroke, which was also self-reported but confirmed by medical record examination.
The lifestyle factors were scored individually, and combined into a health index, including:
- Smoking - categorized as never smoked, past smoker with < 20 pack-years, past smokers with > 20 pack-years, current smokers who smoke > 15 cigarettes a day, or current smokers who smoke < 15 cigarettes a day
- Physical activity - self-reported frequency of weekly strenuous exercise: never, less than once per week, 2-3 times per week, or > 4 times per week
- Body mass index (BMI) - weight in kilograms divided by height in meters squared
- Alcohol consumption - reported as drinks per week or per day: never, less than one, 1-3, 4-10.5, and > 10.5 drinks per week
- Diet - 161 item food-frequency questionnaire
- in the 10 years of follow-up, 450 strokes were recorded (from a sample of > 37 000 subjects)
- participants with a high health index score (17-20 total) had adjusted hazard ratios of 0.45 for total stroke, and 0.29 for ischemic stroke compared to low scoring (0-4 total) participants **
- generally, women who abstained from smoking, exercised regularly, had a low BMI, consumed alcohol moderately, and who consumed a healthy diet had a significantly lower risk of stroke
Conclusions & Practical Application:Despite being a large study, certain limitations are noted by the authors and worth mention here.
- all information on lifestyle factors was self-reported
- the study population consisted of primarily white subjects, so external validity to other ethnic groups may be limited
- residual confounding factors may have influenced results because it is an observational study design