Are two really better than one? Empirical examination of repeat blood pressure measurements and stroke risk in the Renfrew/Pitisley and collaborativestudies
Cl. Hart et al., Are two really better than one? Empirical examination of repeat blood pressure measurements and stroke risk in the Renfrew/Pitisley and collaborativestudies, STROKE, 32(11), 2001, pp. 2697-2699
Background and Purpose-Blood pressure measured on 2 occasions in 2 large pr
ospective cohort studies in Scotland was related to stroke, defined as stro
ke mortality or hospital admission for stroke. The purpose was to investiga
te whether 2 blood pressure readings gave a more accurate estimate of strok
e risk over a long follow-up period than 1 reading.
Methods-In the 1970s, the Renfrew/Paisley general population study investig
ated 3060 men and 3502 women and the Collaborative study investigated 2683
employed men on 2 occasions. The mean years between screening were 4 and 5,
respectively. Blood pressure measured on the 2 occasions was related to st
roke risk in 17-year and 21-year follow-up periods after the second screeni
ng, respectively.
Results-For both systolic and diastolic blood pressure, the mean of the mea
sures on the 2 occasions, the maximum of the 2 measures and the measure cor
rected for regression dilution was more strongly related to stroke over the
follow-up periods than either single measure.
Conclusions-Two blood pressure measurements seem better than 1 for indicati
ng stroke risk. Underestimation using single measures will lead to both mis
classification of the risk of disease for individuals and also the populati
on-attributable risk of disease associated with elevated blood pressure.