Substantial variation in associations hypertension and various CV outcomes

Rapsomaniki E, Timmis A, George J, et al.
Lancet. 2014 May 31;383(9932):1899-911

Background

High blood pressure (BP) was identified as the major risk factor for the overall global burden of disease in 2010 [1]. Changing numbers of people living with or dying from cardiovascular (CV) disease (CVD) and wider use of preventive drugs call for an updated understanding of the associations of BP with non-fatal and fatal CV disease outcomes, to facilitate prevention strategies and design of clinical trials.
Although the Prospective Studies Collaboration meta-analysis yielded important information based on which public health initiatives have been based [2], no estimates are available for the lifetime incidence and years of life lost associated with hypertension attributable to specific CV diseases.
This study aimed to address this in a large contemporary cohort, based on linked electronic health records, with high prevalence use of BP-lowering treatments, and with BP measurements performed as usual clinical practice. Data of 1.258.006 persons of 30 years and older, without previously diagnosed CVD, enrolled in the CALIBER (CArdiovascular research using LInked Bespoke studies and Electronic health Records) programme [3] were analysed.

Main results

• Heterogeneous associations of changes in systolic or diastolic BP (SBP or DBP) with different CV outcomes were observed. SBP was more strongly associated with stable angina, subarachnoid haemorrhage, or intracerebral haemorrhage (HRs all 1.41-1.44), than with total CVD (HR: 1.26, 95%CI: 1.25-1.28). A weak association of SBP was seen with abdominal aortic aneurysm (HR: 1.08, 95%CI: 1.00-1.17 per 20 mmHg).
• DBP showed weaker associations with stable angina, peripheral arterial disease (PAD) and myocardial infarction (MI) and total CVD. The strongest association of DBP was seen with abdominal aortic aneurysm (HR: 1.45, 95%CI: 1.34-1.56) and mean arterial pressure (HR per 10 mm Hg: 1.61, 95%CI: 1.48-1.75).
• Most associations between SBP and clinical outcomes were similar for men and women, except that MI had a stronger association in women than in men.
• Adjustment for CVD risk factors had very little effect on associations between outcomes and BP. Further adjustment for BP-lowering drugs attenuated all associations of SBP or DBP with endpoints by about 20-30%, except for stroke outcomes.
• Substantial variation was seen in the shape of the association between SBP or DBP with different outcomes, at different ages. No evidence for J-shaped associations was seen for any of the outcomes.
• Lifetime risk of total CVD at 30 years of age was 63.3% (95%CI: 62.9-63.8) in people with hypertension and 46.1% (45.5-46.8) in those without. Differently increased risks were seen for people with hypertension as compared to those with healthy BP for individual CVD outcomes.
• The mean number of CVD-free life-years lost associated with hypertension was 5.0 (95%CI: 4.8-5.4) from 30 years of age, 3.4 years (3.3-3.6) from 60 years and 1.6 (1.5-1.7) from 80 years of age. Isolated systolic hypertension accounted for a quarter of the CVD-free years of life lost in those aged 30-59 and for almost half in older subjects, while isolated diastolic hypertension could only explain respectively 0.5% in those 30-59 years, and in a negligible proportion in older age groups.

Conclusion

These data show that, despite modern therapy, a substantial lifetime burden of hypertension remains. Substantial heterogeneity exists across different clinical outcomes and ages for the associations between BP and CV disease. The results also underscore the recent shift of focus in guidelines from DBP towards a greater importance of SBP in patients of 60 years or older.
Based on these findings, it could be postulated that BP acts via different mechanisms in different diseases. Furthermore, this study highlights that BP-lowering strategies are currently insufficient, as indicated by the difference between the lifetime risk curves in people with vs. without hypertension.

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References

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data for one million adults in 61 prospective studies. Lancet 2002; 360: 1903–13.
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