Initiation and follow-up of treatment for high blood pressureBMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h167 (Published 05 February 2015) Cite this as: BMJ 2015;350:h167
- 1Primary Care Unit, Department of Public Health and Primary Care, University of Cambridge, Strangeways Research Laboratory, Cambridge CB1 8RN, UK
- 2Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, OX2 6GG, UK
- Correspondence to: J Mant
High blood pressure is the leading risk factor for disease worldwide.1 Whereas strong evidence from randomised controlled trials is available for some aspects of the management of hypertension, uncertainties remain for others. In the linked article by Xu and colleagues (doi:10.1136/bmj.h158), three of these uncertainties are investigated.2 At what blood pressure threshold should treatment be intensified? How long after a high blood pressure is recorded should treatment be changed? And how long after treatment has been increased should the blood pressure be measured again?
Xu and colleagues used a large electronic database of primary care records from the United Kingdom—The Health Improvement Network (THIN) database—to construct a retrospective cohort of adults with a diagnosis of hypertension. For each patient, they split the data that they had into three time periods: a run-in period of at least 12 months to define baseline characteristics, a treatment period of 10 years from which the three key parameters (intensification threshold, time to intensification, and time to follow-up after intensification) were estimated, and an outcome assessment period. The third period continued until an outcome event had occurred (a cardiovascular event or death from any cause) or follow-up ceased. This elegant design allowed the researchers to answer important questions that do not lend themselves to prospective studies or randomised controlled trials.
Blood pressure thresholds for treatment remain controversial. Observational data suggest that the lower the systolic blood pressure the lower the risk of cardiovascular disease, at least down to 110 mm Hg.3 Meta-analysis of data from trials suggest that the effect of lowering blood pressure is independent of baseline blood pressure.4 However, recent trials of lower targets failed to show benefit, even in patients at higher risk.5 Subsequently, no clinical guidelines for uncomplicated hypertension recommend treatment thresholds below 140 mm Hg and some have reined back on targets.6 7 International guidelines vary as to whether drug treatment should be offered to everyone with a systolic blood pressure between 140 and 160 mm Hg (stage 1 hypertension) or only to those with raised cardiovascular risk, with only scant evidence available from randomised controlled trials at this treatment threshold.6 8
Xu and colleagues found no evidence of clinical benefit associated with an intensification threshold much below 150 mm Hg but acknowledge that they may not have enough power to detect a small effect.2 These data can be viewed as confirmatory from both guideline perspectives—evidence of benefit associated with treating stage 1 hypertension, but not necessarily enough to outweigh the potentially substantial costs of treating the one in 12 adults with uncomplicated stage 1 hypertension.9
How quickly should we intensify treatment for raised blood pressure? Some delay is appropriate, given the variability of blood pressure and the need to confirm that it is truly elevated, whether through repeated measurements over time or use of ambulatory blood pressure monitoring, as recommended by the National Institute for Health and Care Excellence.8 This analysis suggests that the confirmatory process should be completed within six weeks.
When should blood pressure be measured again after treatment intensification? Half of the maximal blood pressure lowering effect is achieved within a week, and the full effect is achieved within four weeks.10 This is consistent with the 2.7 month window observed by Xu and colleagues before risks of cardiovascular events or death start to increase and concurs with trial evidence regarding the effectiveness of structured care and follow-up. 11
Xu and colleagues’ findings should be interpreted bearing in mind the limitations of observational research and of using electronic primary care records. The strength of association between exposure and outcome is likely to have been underestimated, as coding of cardiovascular events and recording of blood pressure are likely to be less accurate in this database than in a prospective cohort study. Furthermore, reducing blood pressure has a weaker effect on all cause mortality than on vascular events.12 The possibility of confounding by indication exists, whereby thresholds or the timing of treatment and follow-up are influenced by patients’ characteristics that were not measured or adjusted for. Confounding by quality of care is also possible—decisions on intensification and timings may be associated with other aspects of the general healthcare provided by the general practice looking after the patient. Finally, patient choice may have been important in the decision not to intensify treatment but will not be captured by this design.
Nevertheless, there are useful messages here for both general practitioners and patients. For general practitioners, this study provides some corroborative evidence for the treatment thresholds advocated by current guidelines and reinforces the importance of timeliness in establishing a diagnosis of hypertension, intensifying treatment when blood pressure remains above target, and scheduling follow-up after treatment intensification. The consequences of clinical inertia are starkly illustrated—60% of patients in Xu and colleagues’ study waited longer than 18 weeks for treatment intensification, and this was associated with around a 20% increase in death or cardiovascular events.
One way of achieving better adherence to guideline thresholds, along with timely intervention and follow-up, is to give more control to patients. Patients who self manage their hypertension achieve lower blood pressures than do those managed with usual care, and patients who simply self monitor also have better control of their blood pressure.13 14 In resource poor settings where access to primary care is limited, fixed dose drug combinations to treat hypertension may also have a role, as this might short circuit the need for further treatment intensification.15
Cite this as: BMJ 2015;350:h167
Competing interests: We have read and understood the BMJ policy on declaration of interests and declare the following interests: JM has no competing interests; RJMcM has received honorariums from the Japanese Hypertension Society for speaking at events funded by Omron and blood pressure monitoring equipment from Omron and Lloyds Pharmacy for research purposes.
Provenance: Commissioned; not externally peer reviewed.
Log in using your username and password
Log in through your institution
Register for a free trial to thebmj.com to receive unlimited access to all content on thebmj.com for 14 days.
Sign up for a free trial