long-term Italian study looked at cardiovasc and total mortality in patients with sustained hypertension (HT) vs true whitecoat hypertension [true WCH — defined as high office blood pressure and normal 24-hr ambulatory blood pressure (ABPM) as well as normal home blood pressure], and partial whitecoat hypertension (partial WCH, defined as high office blood pressure and either high ABPM or home blood pressure) — see doi: 10.1161/HYPERTENSIONAHA.111.00690 . a unique study by making this division of WCH, hoping to clarify the pretty mixed data on clinical outcomes of WCH in the literature. in brief:
–2051 subjects from general population near Milan, Italy followed 16 years
–risk of cardiovascular mortality increased in WCH vs normotensive (RR 2.04) and more so in those with sustained hypertension (RR 2.94). similar increased risks for total mortality
–but, when divide WCH into true vs partial (of which 42% of the WCH group were true and 58% partial), only the partial WCH had increased adjusted cardiovascular (RR 2.76) and all-cause mortality (1.58). no significant increase in those with true WCH. also, notably, those with partial WCH and NOT on antihypertensive therapy did significantly worse than when on bp meds (ie the meds helped)
–10-year risk of developing sustained hypertension was 9.9% in initially normotensive, 35.5% in those with true WCH and 45.5% in those with partial WCH
several issues with this study.
–relatively small number of events (n=48 in the hypertensive group, 21 in total WCH and 8 in normotensives)– would have been better if they included non-fatal events.
–not great cardiac risk factor adjustment — only looked at smoking (only as dichotomous variable, so not include #cigarettes), and only included total cholesterol — measured at baseline
–defined hypertension also as dichotomous — turns out that the actual readings were lowest in those who were normotensive (office BP 117/77), and intermediate in WCH — still considered normal, but office BP was 143/90 but higher in those with partial WCH at 146/91 than those with true WCH (139/90), which could explain some of the difference in outcomes as well as likelihood to progress to sustained hypertension
–i think it makes sense to view ABPM and home monitoring as complementary: ABPM gives lots of data over 24 hours, home-based gives a little data over longer intervals (giving insight into day-to-day variations). in this study office-based blood pressure was assessed by 3 recordings (after pt sitting 10-minutes), ABPM with recordings every 20 minutes, and home-based with 2 recordings (7am and 7pm, using validated semiautomatic device) — but it seems that it was only with 2 recordings!! which likely undercuts its utility
so, this is a really important issue. about 1/3 of pts with hypertension (esp at the lower levels) have WCH, and treating them unnecessarily may well be counterproductive (no real clinical benefit, and lots of negatives: exposure to meds, medicalization). i still think there is important benefit to risk stratify these patients with low levels of office-based hypertension by ABPM and/or home-monitoring (which can be done in the local pharmacies), and basing therapeutic decisions on that. of course, these patients should be followed carefully, since several studies over the years have shown the same as this one — WCH does put patients at higher risk of sustained hypertension.
i will post a prior writing which dealt with WCH, including the NICE guidelines which strongly support assessing non-office based blood pressures, a detailed review article (seer BMJ 2011;342:d3621 doi: 10.1136/bmj.d3621), and reference to a couple of studies which found that office-based blood pressure did not predict clinical outcomes.
Geoff