Life's Simple 7 and Risk of Incident Stroke: The Reasons for Geographic and Racial Differences in Stroke Study.

Kulshreshtha A, Vaccarino V, Judd SE et al.
Stroke. 2013 Jun 6. [Epub ahead of print]

Background

The American Heart Association/American Stroke Association (AHA/ASA) has proposed a metric to be able to define and track the nation’s cardiovascular (CV) health over time [1]. This metric was released as a score called ‘Life’s Simple 7’(LS7). LS7 emphasises primordial prevention and includes 7 modifiable components, consisting of 3 health factors (glucose, cholesterol and blood pressure) and 4 health behaviours (body mass index, physical activity, diet, and cigarette smoking). Each of these factors are categorised into ideal, intermediate and poor levels, and are given scores of 2, 1 or 0 respectively, so the LS7 score can range from 0 to 14. An LS7 score of 0-4 was classified as inadequate, 5-9 as average, and 10-14 as optimum CV health [2, 3].
Recently, more ideal CV health factors from the LS7 metric were shown to be associated with lower CVD and all-cause mortality [4-6]. Less is known about the predictive value of a composite measure of biological and behavioural risk factors for stroke. Using data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study the association between LS7 and incident stroke was investigated, and racial differences were examined. The REGARDS study is a population-based cohort study of US adults of >45 years old, with a large proportion of blacks. 22914 participants without previous CVD were included, 9553 of whom were blacks.

Main results

• Male sex, low income, less education and current alcohol use were associated with poorer CV health in both blacks and whites.
• More whites were in the optimum CV health category (19%) than blacks (7%), irrespective of age, sex, income, education and geographic region. Mean (+SD) overall LS7 score was 7.2 (2.2). Adjusting for age and sex, blacks had a lower mean score (6.5+2.0) than whites (7.6+2.1).
• During 4.9 years of follow-up, there were 432 incident strokes, of which 232 occurred in whites. For some LS7 components stroke incidence was lowest in those with an ideal score, and highest in those with poor CV health status. Adjusted HRs for total cholesterol, blood pressure, blood glucose and smoking showed a graded relationship with stroke, in particular among whites.
• Worse overall LS7 score was inversely correlated with incident stroke in a graded fashion. In a multivariate model, each better health category was associated with a 25% lower risk of incident stroke (HR: 0.75, 95%CI: 0.63-0.90).
  Although the association of LS7 category and stroke did not reach statistical significance in blacks, crude and adjusted HRs were similar for blacks and whites.
• When considering total LS7 score on a continuous scale from 0-14, a 1 point higher LS7 score was associated with 8% lower risk of stroke (HR: 0.92, 95%CI: 0.88-0.95), which was similar in blacks and whites. An increasing number of ideal factors was inversely associated with risk of stroke in both blacks and whites, even when changing from 0 to 1 ideal factor (HR: 0.70, 95%CI: 0.42-1.19).

Conclusion

The LS7 metric was developed as part of AHA’s strategic impact goal to improve the CV health of all Americans. This study shows that it is a useful tool to describe the risk of incident stroke. Although blacks showed lower levels of ideal factors, the association of LS7 and stroke did not differ between blacks and whites. Improvement of a single health behaviour can reduce stroke risk. These findings support the hypothesis that small shifts in the population distribution of risk factors can have a dramatic impact on reducing the disease burden in populations.

References

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