Wrist actigraph measures of physical activity level and ambulatory blood pressure in healthy elderly persons

A sensitive electronic monitor (Mini-Motionlogger, Ambulatory Monitoring Inc.) attached to the wrist was used to record movements during two 24-hr days of ambulatory blood pressure (BP) and heart rate (HR) recording in 65 women and 54 men between the ages of 55 and 79 years, all of whom were in good health. The objective was to examine the relationship between various measures of physical activity and ambulatory BP and HR during waking and sleeping periods and during various diary-defined behaviors. For waking and sleeping periods, neither the mean nor the variability of the activity measure was associated with the mean or variability of the ambulatory BP and HR measures in between-subjects correlational analyses. Within-subject analyses showed little evidence of significant covariation between activity and BP or HR during either waking or sleeping conditions with most participants showing a slightly positive association. The activity measure discriminated between behaviors associated with little effort (watching television) versus more energetic behaviors (walking). Activity accounted for a relatively small amount of the difference in BP or HR related to overall state (wake, sleep), posture (stand, sit), and social condition (being with family vs. being with friends). The utility of electronic activity monitoring for studies of BP and HR in natural settings is discussed.