Background: Effects of catastrophic stress on blood pressure are well documented, but usually few measurements were taken before the event occurred, and the people studied were directly involved or geographically close to the disaster. The impact of the 11 September 2001 (9/11) attacks in New York City had far greater reach, and has been sustained by subsequent events.
Objective: To test the hypothesis that, after the 9/11 attacks, blood pressures in the population affected would be increased compared with that in both the preceding months and the same period during the previous year.
Methods: We used data available from a current study of blood pressure in four sites in the USA that enabled us to examine them from two perspectives: a mixed (within and between groups) analysis that tested the overall differences in blood pressure before and after 9/11, and a within-subjects model to examine the more focused issue of individual change in blood pressure after 9/11. The blood pressures of 427 hypertensive individuals were telemonitored at four sites. An additional 101 patients had been monitored at two sites during the same period in the previous year.
Results: Mean systolic blood pressure was significantly greater during the 2 months after 9/11, across the four sites, compared with that assessed during the previous 2 months (range of observed differences 1.7-3.8 mmHg). At the two sites for which data were available for the same period in the year 2000, there was also a significant effect for the same period during the preceding year for systolic blood pressure. However, at both these sites the effect at 2000 was significantly smaller than the effect at 2001. Blood pressure also generally increased among those individuals in whom monitoring overlapped the 9/11 event.
Conclusion: The World Trade Center attacks produced a substantial and sustained increase in blood pressure that appears to be independent of seasonal effects, and which has important implications for morbidity and financial burden. The ubiquitous continuing reference to the events in the news reports may contribute to the sustained effects.