[A study on 24-hour ambulatory blood pressure in normotensive elderly, living in a local home for the aged]. 
Ambulatory blood pressure (BP) was non-invasively monitored in 124 normotensive elderly, living in an old people's home at the annual health examination.  Cases were divided into 41 cases < 75 years (group A, mean age 70.6) and 83 cases > or = 75 years (group B, 82.7) for analysis of the office BP and 24-hour BP.  Whole-day systolic BP in group B was significantly higher than those in the group A (p < 0.02) although no significant differences were observed in diastolic BP and pulse rate.  Separated analysis of whole-day BP into daytime and nighttime revealed that the nighttime systolic BP in the group B was significantly higher than those in group A (132.2 +/- 17.4% vs. 123.8 +/- 18.6 mmHg, p < 0.02) whereas no significant difference was observed in day-time systolic BP between two groups (136.6 +/- 14.9 vs. 132.1 +/- 14.4 mmHg, n.s.).  The day-night difference in systolic BP tended to be less in group B than in group A (4.5 +/- 11.6 vs. 8.2 +/- 12.2 mmHg, p < 0.10).  The prevalence of non-dippers, who had a higher nighttime systolic BP than daytime systolic BP were 24.4% of the group A and 30.1% of the group B. It was concluded that systolic BP during the nighttime increased with the ageing process after age 60, although that during daytime did not change.