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Table 1 Mean number of days per year defined as heatwave days (across 53 locations) for various heatwave definitions

From: Acute associations between heatwaves and preterm and early-term birth in 50 US metropolitan areas: a matched case-control study

  97.5th percentile of temperature 85th percentile of EHF (+)
Tmin ATmin Tmax ATmax Tmean ATmean Tmin ATmin Tmax ATmax Tmean ATmean
HW1 (na, SDb)
 0 334.4 (3.7) 334.4 (3.8) 337.7 (4.3) 338.2 (4.2) 338.0 (4.0) 337.0 (4.0) 357.3 (1.5) 357.5 (1.5) 357.1 (1.8) 357.1 (1.6) 357.1 (1.9) 357.4 (1.8)
 1 14.2 (3.4) 14.3 (3.5) 10.7 (3.4) 10.3 (3.2) 10.3 (3.2) 11.6 (3.3) 3.7 (1.4) 3.8 (1.5) 3.1 (1.3) 3.3 (1.5) 3.3 (1.6) 3.3 (1.5)
 2 7.8 (2.0) 8.0 (2.0) 7.0 (2.2) 7.2 (2.3) 7.2 (2.2) 7.4 (2.0) 2.3 (0.9) 2.0 (1.0) 2.8 (1.2) 2.6 (1.0) 2.6 (1.2) 2.4 (1.3)
 3 or more 8.9 (1.5) 8.5 (1.5) 9.9 (2.0) 9.6 (1.5) 9.9 (1.6) 9.3 (1.5) 2.0 (0.6) 2.0 (0.6) 2.3 (1.0) 2.3 (0.9) 2.4 (0.9) 2.2 (0.9)
HW2 (na, SDb)
  ≥ 2 consec. Days 14.6 (1.8) 14.6 (1.8) 16.0 (2.0) 16.1 (2.2) 16.1 (2.4) 15.4 (2.3) 4.2 (0.9) 4.0 (1.1) 5.0 (1.1) 4.8 (0.9) 4.8 (1.1) 4.5 (0.9)
  ≥ 3 consec. Days 6.9 (1.5) 6.5 (1.6) 8.7 (1.9) 8.2 (1.5) 8.4 (1.5) 7.8 (1.5) 1.9 (0.6) 1.9 (0.6) 2.3 (1.0) 2.3 (0.9) 2.3 (0.8) 2.1 (0.9)
  ≥ 4 consec. Days 3.2 (1.2) 3.2 (1.1) 4.4 (1.6) 4.2 (1.5) 4.3 (1.5) 3.8 (1.3) 0.8 (0.4) 0.8 (0.3) 1.0 (0.4) 1.2 (0.5) 1.0 (0.5) 0.9 (0.4)
HW3
 na(SDb) 3.3 (1.2) 3.3 (1.1) 4.5 (1.8) 4.1 (1.5) 4.3 (1.4) 4.0 (1.2) 0.9 (0.4) 0.9 (0.5) 1.2 (0.6) 1.1 (0.6) 1.0 (0.5) 0.9 (0.5)
 AUC (°C/°C2, mean (SDc)) 0.52 (0.52) 0.78 (0.81) 0.76 (0.67) 0.91 (0.78) 0.57 (0.51) 0.83 (0.80) 1.2 (1.1) 2.4 (2.3) 3.7 (4.3) 3.8 (4.1) 1.4 (1.5) 2.6 (2.7)
  1. Note: Excessive heat factor (EHF); HW1: the total number of hot days in the previous week (sum the number meeting the definition (ranging from 0 to 7)); HW2: number of consecutive hot days in the past week (binary indicators for 2, 3 and 4 consecutive days); HW3: area under the curve (AUC) during the previous week
  2. a n is the mean annual number of days meeting the exposure definition across 53 locations
  3. b Standard deviation (SD), describes the variation of number of days per year across 53 locations
  4. c Standard deviation (SD), describes the variation of area under the curve (AUC) across 53 locations and all years