shift as part of a swing shift work schedule (e.g., Sundburg et al. 1988 ; Baumgart
et al. 1989 ; Yamasaki et al. 1998 ).
Posture and Physical Activity
As in laboratory studies, posture has been found to also have a substantial effect on
diurnally assessed ambulatory blood pressure variability (James 2013 ). Analyses of
ecological momentary blood pressure data consistently show that pressures taken
while standing are substantially higher during the day than pressures while sitting or
reclining (see James2007bfor review), although pressures taken while sleeping and
reclining are lower than pressures taken while awake and reclining (James et al.
2001 ) The effects of posture will often covary with physical activity, as most diary
reportable activities tend to occur in a single posture; thus in most studies that
evaluate the effect of posture, the effects of activity are not estimated (James 2013 ).
Researchers who have assessed the effects of changing daily activitiesfind that
those which require significant movement (from walking to doing household
chores) elevate pressures the most, whereas activities which require mental effort
such as reading or writing or other activities that are generally quiescent, such as
eating, watching TV, or talking have less effect (see James2007bfor review). It
should be noted that the estimated effects of the more physically active activities are
generally underestimates, because the monitors will malfunction and not take a
pressure correctly unless the subject stops moving and remains still for the entire
cycle of the ambulatory blood pressure measurement (usually 30–40 s) (James
2013 ). Figure8.5presents some estimated effects of various activities on ambu-
latory blood pressures (from James 2013 ).
Finally, other studies have assessed the effects of physical activity using actig-
raphy (e.g., Gretler et al. 1993 ; Kario et al. 2001 ). From this work, it has been
estimated that about one-third of the variance among intermittently sampled
ambulatory pressures is related to the constant change in motion during the day
(James 2013 ).
Emotional State
Thefirst study regarding the ecological momentary effects of mood on automatic
ambulatory blood pressure measurements (James et al. 1986 ) showed that reported
happiness, anger, and anxiety increased blood pressure to differing degrees and that
the effects varied with mood intensity (James 2013 ). Subsequent studies have
generally confirmed thisfinding (see James2007bfor review). However, many
studies have reported that the size of the effect of emotion on blood pressure
depends on the situation, and other factors such as gender and season of the year
can also moderate the effects (see James2007b). Figure8.6presents estimated
8 Continuous Blood Pressure Variation: Hidden Adaptability 155