Wednesday, January 28, 2015

Guest Post: Apples, oranges, and treating mild hypertension

- Stephen Martin, MD

A recent systematic review published in the Annals of Internal Medicine (and discussed by Dr. Lin in a previous post) revisited the potential efficacy of drug treatment for mild hypertension. The authors concluded that this treatment “in the primary preventive setting is likely to reduce the risk for several important adverse health outcomes.” This is an interesting finding, given that a 2012 Cochrane review found no evidence of mortality or morbidity benefits from drug treatment of mild hypertension. What changed?

The Annals authors explain their different conclusions as follows (italics mine): “Besides the inclusion of persons with diabetes or prior antihypertensive treatment, the disparity between the conclusions of this review and the one immediately preceding it is primarily attributable to statistical power. The present review nearly doubled the number of patients, quadrupled the number of cardiovascular events, and provides data on end points not available in the prior meta-analysis.”

Having recently examined this literature for our BMJ piece, “Mild hypertension in people at low risk,” my interpretation is different. In order to gain statistical power, the new review combined high-risk and low-risk patients with mild hypertension. This is equivalent of mixing apples—e.g., higher-risk people with diabetes and prior treatment—with oranges— people without diabetes or prior treatment of hypertension.

To summarize this systematic review a bit differently, I derived the table below from Annals Appendix Table 3 and assigned the sources of patients as being oranges (Cochrane) or apples (BPLTTC Trials):

Cochrane (Oranges)
BPLTTC Trials (Apples)
Difference (Apples/Oranges)
Active Participants
4,478
3,364
Diabetes (%)
0
96
Previous antihypertensive treatment (%)
0
62
Total Deaths
(#, events per participant)
77 (0.018)
230 (0.068)
3.78 (0.068/0.018)
Cardiovascular Deaths
NA*
96 (0.029)
NC^
Strokes
10 (0.002)
89 (0.026)
13 (0.026/0.002)
Coronary Events
71 (0.016)
114 (0.034)    
2.13 (0.034/0.016)
Heart Failure
NA
62
NC

* NA = “Not Available,” which occurred for individual trials in the Cochrane and BPLTTC, more so the former (see Appendix Table 3 link above)

Unfortunately, these subtleties were absent from the journal’s communication to the mainstream media, which simply stated: “Blood pressure drugs likely to prevent stroke and death in patients with mild hypertension.”

There is hope yet. The paper buried a worthy point when it concluded that “… estimation of cardiovascular risk may aid prioritization in this patient group.” Rather than combining apples and oranges, we need to treat them as different fruit. Apples may benefit from treatment of mild hypertension while oranges do not. Blending them serves neither fruit well.

For now, I’ll continue to generally avoid drug treatment for my low-risk patients with mild hypertension.

**

Dr. Martin is a family physician and an Assistant Professor at University of Massachusetts Medical School.

1 comment:

  1. This is a great message. Let's push back and help more patients by avoiding unnecessary medical interventions. Thank you Dr. Martin (and Kenny).

    ReplyDelete