Letter regarding article by Sega et al, "Prognostic value of ambulatory and home blood pressures compared with office blood pressure in the general population".

“Prognostic Value of Ambulatory and Home Blood Pressures Compared With Office Blood Pressure in the General Population” To the Editor: We read with interest the paper by Sega et al regarding the prognostic value of ambulatory, home, and office blood pressure in the PAMELA population.1 However, we find that the main conclusions of the report may be driven by the lack of adjustment for confounders. The relationships between level of blood pressure and risk were not adjusted for age, which may have a major influence on risk over a long time span. There is indeed a relation between age and blood pressure,2 and therefore, these results may be biased. The comparisons of the various blood pressures were also not adjusted for potential confounders, with the argument that “no adjustment for age, sex, and other cardiovascular risk factors was made because comparisons between the predictive value of various blood pressure values involved the same sample.” However, it has been shown in a general Belgian population that the within-subject differences between office and ambulatory blood pressure measurements increased with older age and greater body mass index.3 In addition, in the Danish MONICA population, the within-subject differences between office and ambulatory blood pressure measurements increased with older age, diagnosis of hypertension, male gender, and presence of diabetes.4 So, to assess the true prognostic value of office blood pressure versus that of ambulatory blood pressure, it is mandatory to explore whether adjustments for other relevant cardiovascular risk factors would change the results. Recently, it was shown in the Danish MONICA population that ambulatory blood pressure was a much better predictor of all-cause mortality and cardiovascular mortality than office blood pressure, taking other relevant risk factors into account.5 Accordingly, to make the results from previous studies comparable to the PAMELA study, we would like to know the results of adjusted analyses. Until that time, the conclusion that “office, home, and ambulatory blood pressures are similarly predictive of the risk of cardiovascular and all-cause death” needs to be interpreted with caution.