ESC Congress 2026 Abstract · Oct 26, 2026
Does outdoor temperature modify the prognostic value of 24-hour ambulatory systolic blood pressure? the IDACO Study
By Wang Y, Shi H, Yang Z et al.
Background: Ambient temperature influences blood pressure (BP), but whether outdoor temperature around the time of ambulatory BP monitoring affects the prognostic interpretation of systolic blood pressure (SBP) for long-term outcomes remains uncertain. Methods: We analyzed 14,236 participants from the International Database on Ambulatory Blood Pressure in Relation to Cardiovascular Outcomes (IDACO). Outdoor temperature was summarized as mean temperature over three exposure windows: same-day (1-d), 7-day, and 30-day periods around the ambulatory BP recording. Cohort-specific associations between outdoor temperature and 24-hour SBP were assessed using linear regression. To evaluate whether temperature-related measurement variation affects risk stratification, we derived temperature-standardized 24-hour SBP for each exposure window by standardizing SBP to the cohort-specific median temperature. Cox proportional hazards models estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for total mortality and a composite cardiovascular endpoint. Incremental predictive performance was assessed using Harrell’s C-index, likelihood ratio tests, net reclassification improvement (NRI), and integrated discrimination improvement (IDI). Adjusted cumulative incidence curves were generated by quartiles of observed and temperature-standardized 24-hour SBP (adjusted for cohort, sex, and age). Results: Associations between outdoor temperature and 24-hour SBP varied across cohorts and exposure windows (1-d, 7-d, and 30-d), with both positive and negative cohort-specific slopes. In Cox models, the HRs per 20 mm Hg higher observed 24-hour SBP were 1.23 (95% CI 1.17–1.30) for total mortality and 1.47 (1.39–1.55) for cardiovascular endpoints (both P<0.001), and these estimates were essentially unchanged when using temperature-standardized 24-hour SBP. In prediction analyses, adding observed 24-hour SBP increased the C-index from 0.8267 to 0.8293 for total mortality and from 0.8141 to 0.8246 for cardiovascular endpoints, with NRI 4.7% (0.36 to 8.4) and 11.0% (6.7 to 14.2), respectively. Temperature-standardized SBP (1-d, 7-d, or 30-d) yielded similar C-index values and did not consistently improve NRI or IDI compared with observed SBP. Conclusions: Outdoor temperature around the time of ambulatory BP monitoring is associated with 24-hour SBP in a cohort-dependent manner, but temperature standardization of SBP provides limited incremental benefit for long-term risk stratification beyond observed ambulatory SBP.