Framingham, MA - A new analysis of data from the Framingham Heart Study shows that blood pressure (BP) levels in the community have improved over time, likely due to the widespread introduction of antihypertensive therapy [1]. Dr Erik Ingelsson (Karolinska Institute, Sweden)—who was with the Framingham Heart Study at the time of this research—and colleagues report their findings in July 14, 2008 issue of the Archives of Internal Medicine.

They also found an BP-attenuation/mortality relationship, coinciding with the improved rates of hypertension control, and although the study is observational, "our findings are consistent with the hypothesis that treatment of hypertension has had a profound effect on outcome at the community level," they say.

To their knowledge, they say this is the first contemporary attempt to track the effect of BP progression on cardiovascular-disease incidence and all-cause mortality.

Ingelsson et al used data from Framingham that, with its more than 50 years of repeated BP measurements and follow-ups, "provides a unique opportunity," they stress.

They evaluated trends for three BP variables (long-term slope and mean BP during a baseline period of 16 years and last baseline value) in an earlier period (1953-1971; n=1644) and in a later period (1971-1990; n=1040) in participants in the Framingham Heart Study who initially did not have hypertension.

In addition, they explored the relation of BP to cardiovascular-disease incidence and mortality in the two periods, each with 16 years of follow-up. They note that the time periods studied are ideally placed to compare the situation before and after widespread introduction of antihypertensive therapy.

Long-term slope, mean, and last baseline BP measurements were significantly lower in the later period (p<0.001), and rates of hypertension control (BP<140/90 mm Hg) were higher in the later vs the earlier period (32% vs 23%, p<0.001).

In addition, multivariate adjusted hazard ratios for the relation of BP to outcomes were generally lower in the later period; this was significant for the relation of last baseline BP to all-cause mortality (HR for one-standard-deviation increase in systolic BP, 1.02 vs 1.25 [p=0.03]; and HR for diastolic BP, 1.00 vs 1.23 [p=0.04]).

First, the findings are consistent with an important effect of treatment on the long-term consequences of hypertension, the researchers say. Second, a significantly higher proportion of individuals with hypertension in the later period received treatment and achieved BP control. Finally, the BP slope was significantly less steep in the later period compared with the earlier period.

"Together these observations support the hypothesis that the widespread introduction and adoption of antihypertensive therapy has altered the natural history of BP progression and the relations of BP to outcome in the community," they observe.

One other important implication of the study is that the BP slope did not have an incremental predictive value over and beyond that of mean or last baseline BP measurements, and so the decision to treat high BP is best guided by the actual level of pressure "and not by its long-term trend in the past," say Ingelsson et al.

Another observation from the present study that might have importance for planning future clinical trials is that "none of the BP variables predicted all-cause mortality in the later period," they point out. This "suggests that all-cause mortality might not be the best choice of a primary end point in future treatment trials in patients with hypertension."

They note the usual strengths and limitations applicable to the Framingham Heart Study; for example, the fact that the sample predominantly comprised middle-aged white people—previous work has shown that the percentage of patients with hypertension who achieve BP control differs between white and ethnic-minority subjects.

Nevertheless, they conclude, "Our findings underscore the opportunity to improve public health by applying existing recommendations for treatment of hypertension. This may be especially true in Europe and other regions of the world where BP control rates lag behind those in the US."