Close Association between day-to-day Fluctuation of Atmospheric Pressure and Blood Pressure in Community-Dwelling People

Prevalence of hypertension is increasing recently in our survey in people in high-altitude areas. In high-altitude areas weather is very changeable and some people move to the level of different altitude in the cycle of the seasons for the livestook farming. There have been many reports about contributing factors to the regulation of BP,i.e. circadian rhythm of BP and its association with circulatory diseases. Recently the effects of climate to BP, and geomagnetics to heart rate variability and diseases are investigated. But there are few reports on the association between atmospheric pressure (AP) and blood pressure (BP). Home BP was examined in community-dwelling people in a rural Japanese town, Kahoku in this study. The association between 14 consecutive day-to-day fluctuation of AP and SBP was studied. The subjects were 406 community -dwelling residents (178 men and 228 women) aged 15 years or older, mean(SD) age 64.8(14.4) years. BP was measured by themselves by automatic sphygmomanometers early in the morning about 7 o'clock in a sitting position for 14 days. Average AP of each day was measured by Kochi Meteorological Observatory only 25km away from Kahoku town. The association between day-to-day 14 pairs of AP and SBP was analyzed by linear regression analysis (P<0.05 :statistically significant). In consideration of the time lag or precedence of the response of SBP to AP, in each person we calculated 7 regression coefficients, i.e. those between 14 pairs of SBP and AP of the same day, one day before, two days before, three days before, one day after, two days after, and three days after. By the most significant regression coefficient of each subject we assigned all people into 7 groups of significant association of SBP and AP from 3-days-before to 3-days-after, or a group of no association. In this analysis, surprisingly many people (42.1%) showed significant positive (21.7%, R=0.52~0.88, p<0.05) or negative (20.4%, R=-0.52~-0.86, p<0.05) correlation between SBP and AP. If probability level was extended to p<0.1, 55.9% of subjects showed possible correlation. 22 subjects (5.3% of 406 subjects) showed most significant positive (3.1%) and negative(2.2%) correlation between 14 pairs of SBP and AP of the same day, similarly 20 people (4.8%) between SBP and AP of one day before, 27 people (6.5%) between SBP and AP of one day after , 24 people (5.7%) between SBP and AP of two days before, 24 people (8.1%) between SBP and AP of two days after ,18 people (4.3%) between SBP and AP of three days before, and 26 people (6.2%) between SBP and AP of three days after showed most significant correlation. 196 subjects, about half of all subjects, measured their home BP at the same 14 consecutive days (6th~19th March). 7 waveforms of average SBP of 14 consecutive days were showed, measured by the subjects whose fluctuation of SBP was most significantly correlated with that of AP of 3-days-before to 3-days-after with the waveform of AP of 20 consecutive days, 3th~22th March. Waveforms of SBP were positively correlated with AP and negatively correlated with AP. Waveforms of SBP were very similar to that of AP. AP fluctuated from 1003.2 hpa to 1025.0 hpa and accordingly SBP fluctuated within the range of 15 to 35 mmHg. These results showed close association between day-to-day fluctuation of AP and BP in consideration of various responsiveness of BP to AP, ie there were time lag and precedence of response of BP over AP, which is probably due to high sensitivity of BP to initial changes of AP. In conclusion the association between 14 consecutive day-to-day fluctuation of atmospheric pressure(AP) and systolic blood pressure(SBP) was shown in community-dwelling people in consideration of time lag or precedence of the response of SBP to AP within a few days. Many subjects (42.1%) showed significant positive (21.7%, R=0.52~ 0.88, p<0.05) or negative (20.4%, R=-0.52~ -0.86, p<0.05) correlation between AP and SBP. t may be needed to investigate further about the effects of AP on human autonomic nervous system and also the association between AP and human physiological or pathological conditions.