WHAT METHOD SHOULD BE USED TO DEFINE NIGHT WHEN ASSESSING DIURNAL SYSTOLIC BLOOD-PRESSURE VARIATION IN THE ELDERLY

Diurnal blood pressure (BP) variation can be assessed by cusums-derive d measures and by the day-night BP difference from time-, activity- an d diary-defined 'night' periods. Reproducibility of diurnal systolic B P (SEP) variation by these different methods was studied in 19 active elderly normotensives, mean age 68.5 years. Subjects underwent simulta neous 24 h BP (Spacelabs 90207) and activity (Gaehwiler wrist actigrap h) monitoring on two occasions (median interval 70 days). On the first occasion, mean diurnal SEP variation was 15.1 +/- 8.1 mm Hg by fixed- time definition of 'night' (22-07). When compared with 22-07 defined ' night' period, actigraph- and diary-defined 'night-time' was significa ntly reduced (-60 +/- 49, and -48 +/- 51 min, respectively) and conseq uently diurnal SEP variation was significantly greater at 18.2 +/- 8.1 mm Hg and 17.6 +/- 8.4 mm Hg, respectively. Actigraph recordings were also used to exclude 'night' BP readings associated with activity, bu t this did not significantly alter the diurnal SEP variation. Cusums-d erived circadian alteration magnitude resulted in the greatest value f or SEP variation (23.4 +/- 6.7 mm Hg). However, reproducibility of diu rnal SEP variation was poor by fixed-time method with a coefficient of variation (CV) of > 50%, and only improved to 40% with diary use. Act igraph measurements, even if used to exclude BP values associated with disturbed sleep, did not improve this further. Cusums-derived measure s of diurnal variation slightly improved reproducibility with a CV of 34.6% and may be a better method in the assessment of diurnal BP varia tion in the elderly.