Four Health Behaviors Combined Help Predict Stroke Incidence *News Author: Laurie Barclay, MD CME Author: Désirée Lie, MD, MSEd * Disclosures <http://www.medscape.com/viewarticle/588615_author> *Release Date: February 24, 2009*;
February 24, 2009 — Four health behaviors combined predict more than a 2-fold difference in stroke incidence in men and women, according to the results of a population-based prospective study reported in the February 20 Online First issue of the *BMJ*. "Lifestyle behaviours such as smoking, physical activity, and diet influence the risk of cardiovascular disease, including stroke," write Phyo K. Myint, from School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, United Kingdom, and colleagues. "Previously we looked at the combined impact of four health behaviours — smoking, physical activity, alcohol intake, and fruit and vegetable intake — on total and cause specific mortality in men and women living in the general community. As these health behaviours could beneficially affect the incidence of stroke we examined the potential magnitude of their combined impact on incidence of stroke in men and women aged 40-79." In the European Prospective Investigation of Cancer–Norfolk study, adults living in the general community in Norfolk, United Kingdom, were followed up to 2007. The study cohort consisted of 20,040 men and women aged 40 to 79 years with no known stroke or myocardial infarction when surveyed at baseline from 1993 to 1997. Participants were scored from 0 to 4, receiving 1 point for each of the following health behaviors: current nonsmoking; physically not inactive; moderate alcohol intake (1 - 14 units a week); and fruit and vegetable intake of 5 or more servings daily, as reflected by plasma concentration of vitamin C of 50 μmol/L or more. Average follow-up was 11.5 years. During 229,993 person-years of follow-up, there were 599 incident strokes. Compared with people with all 4 health behaviors, the relative risks for stroke for men and women were 1.15 (95% confidence interval [CI], 0.89 - 1.49) for 3 health behaviors, 1.58 (95% CI, 1.22 - 2.05) for 2 health behaviors, 2.18 (95% CI, 1.63 - 2.92) for 1 health behavior, and 2.31 (95% CI, 1.33 - 4.02) for no health behaviors (*P* < .001 for trend), after adjustment for age, sex, body mass index (BMI), systolic blood pressure, cholesterol concentration, history of diabetes and aspirin use, and social class. Subgroups based on sex, age, BMI, and social class all had similar findings. Exclusion of deaths within 2 years also did not affect the observed pattern of results. "Four health behaviours combined predict more than a twofold difference in incidence of stroke in men and women," the study authors write. "These results provide further incentive and support for the notion that small differences in lifestyle can have a substantial potential impact on risk." Limitations of this study include possible reverse causality or residual confounding, potential measurement errors in the assessment of exposures, relatively high proportions of the population with some or all positive health behaviors, exclusion of approximately 9000 participants who consented to the study but were unable to attend the health check, and possible misclassification of stroke vs nonstroke. In an accompanying editorial, Dr. Matthew F. Giles, from the Stroke Prevention Research Unit, Biomedical Research Centre, John Radcliffe Hospital, Oxford, United Kingdom, notes additional limitations of the study, including failure to differentiate ischemic and hemorrhagic strokes, and use of vitamin C concentration only as a surrogate marker for fruit and vegetable intake. "It is encouraging that the association between the risk of stroke and combined health behaviour is consistent across different populations, and between observational and randomised controlled trials," Dr. Giles writes. "The conclusion that lifestyle predicts the risk of stroke should help to inform individuals' choices and policy makers' decisions. However, what is also consistent but less encouraging is the small proportion of participants with a lifestyle that protects against stroke — although lifestyle interventions could be of great benefit, a huge shift in behaviour will be needed to achieve this." *European Prospective Investigation of Cancer–Norfolk is supported by research program grant funding from Cancer Research United Kingdom and the Medical Research Council, with additional support from the Stroke Association, British Heart Foundation, Research Into Ageing, Academy of Medical Sciences, and Wellcome Trust. The study authors and Dr. Giles have disclosed no relevant financial relationships.* *BMJ*. Published online February 20, 2009. Clinical Context Lifestyle behaviors such as smoking, physical activity, diet, and alcohol intake can influence cardiovascular risk, but the role of these behaviors in influencing risk in the general population is not well known. For example, other studies have reported a decrease in the incidence of myocardial infarction associated with reduction in cigarette smoking. This is a longitudinal prospective cohort study to examine the impact of adherence to the modifiable behaviors and the risk for stroke in community-dwelling men and women in 1 region of the United Kingdom who were followed up in the European Prospective Investigation of Cancer–Norfolk study. Study Highlights - Included were 20,040 men and women aged 40 to 79 years at baseline recruited from an age-sex register of general practitioners with a population-based sampling frame. - At baseline from 1993 to 1997, patients completed a detailed health and lifestyle questionnaire and listed medical conditions. - The lifestyle behaviors examined were smoking, alcohol intake, intake of fruits and vegetables verified by vitamin C levels, and physical activity. - 4 separate categories were used for alcohol intake. - 1 unit of alcohol was defined as 8 g and equivalent to a half pint of beer or a glass of wine, or a unit of spirits (liquor) and total alcohol consumption were estimated as units consumed per week. - A moderate drinker was defined as someone drinking 1 or more units per week but less than 14 units per week. - Physical activity was assessed during the previous year and was validated against heart rate monitoring. - A physically inactive person was defined as having a sedentary job with no recreational activity. - A physically not inactive person was defined as a person with any activity above that of a physically inactive person. - Trained nurses made anthropomorphic measurements, and a blood level for vitamin C was determined as a biomarker of fruit and vegetable intake. - Participants scored 1 point for each positive behavior: currently not smoking, physically not inactive, moderate alcohol intake (1 - 14 units per week), and plasma vitamin C concentration of 50 μmol/L or higher indicating vegetable and fruit intake of at least 5 servings a day. - The score range was 0 to 4 for combined health behaviors. - Incident cases of stroke were ascertained by death certificate data and hospital record linkage, and trained nosologists coded death certificates. - There were 599 strokes during 229,992 person-years of follow-up (average, 11.5 years). - Of the stroke cases, 28% were fetal. - Among participants, mean age was 58 years, almost half were men, BMI was 26.5 kg/m2, mean systolic blood pressure was 135 mm Hg, and total cholesterol concentration was 6.2 mmol/L. - In the sample, men were older, had higher BMI and higher systolic blood pressure, and were more likely than women to be current or former smokers. - The also consumed more alcohol weekly, were more physically active, and were less likely to consume 5 or more servings of fruits and vegetables daily. - A significantly higher proportion of women scored 4 for combined health behaviors vs men, but the incidence of stroke was not significantly different for men vs women. - The risk for stroke increased in a linear fashion for every 1-point decrease in combined health behavior score. - Men and women who scored 0 for combined health behaviors had a 2.3 times increased risk for stroke (relative risk, 2.31) vs those who scored 4. - The findings were consistent after adjustment for age, sex, BMI, and social class. - The absolute risks for incident stroke were 1.7%, 2.4%, 4.0%, 6.1%, and 5.8% for health behavior scores of 4, 3, 2, 1, and 0, respectively. - The relative risks for stroke vs those with a score of 4, after adjustment, were 1.15 for a score of 3 health behaviors, 1.58 for a score of 2 health behaviors, 2.18 for a score of 1 health behavior, and 2.31 for a health behavior score of 0. - The authors concluded that the combined impact of 4 modifiable lifestyle behaviors resulted in a significant reduction in the risk for stroke for both men and women. Pearls for Practice - Four lifestyle behaviors that influence stroke risk are not smoking, physical activity, moderate alcohol consumption, and eating at least 5 servings of fruits and vegetables daily. - Adherence to all 4 health behaviors is associated with a 2.3 times lower risk for stroke vs adherence to none of these behaviors.
