Background: Directly measured blood pressure (BP) data have not been collected in Canada since the Canadian Heart Health Surveys, conducted between 1985 and 1992. Because hypertension is often asymptomatic, a large proportion of those with the condition are unaware of it.
Data and methods: These analyses use BP and heart rate (HR) data from cycle 1 of the 2007-2009 Canadian Health Measures Survey (CHMS) for respondents aged 6 to 79 years. Methods and quality assurance and control procedures are explained. Logistical and feasibility issues that arose during data collection are discussed. The reasons for repeating a series of measures are given. Between- and within- series variations and inter-tester variability are assessed.
Results: The BP and HR of almost all respondents who attended the examination centre were measured. Only one series of measurements was taken for 88% of respondents. The series was repeated for around 5% with variability in their BP or HR measurements. About 3% had HR or BP values above the screening cut-offs for the fitness tests. Almost 35% of respondents with HR or BP values above the screening cut-offs after their first series had values below the cut-points after the second series; a further 3% had values below after the third series. Within a series of six measurements, BP decreased until about the fourth measure, after which it remained stable. Mean BP and HR values indicated no inter-tester variability.
Interpretation: The protocol for measuring BP and HR by oscillometry in the CHMS appears to have produced reliable estimates. No benefit to repeating the series of six measurements a third time for screening purposes is evident. Four measurements may be sufficient to provide reliable BP and HR data. Oscillometry appears to eliminate inter-tester variability.