Table 4

Baseline characteristics of the study participants by quartiles of ambulatory daytime systolic blood pressure load

CharacteristicsQ1
(n=953)
Q2
(n=1036)
Q3
(n=971)
Q4
(n=996)
Limits (%)<3.23.2–13.713.8–37.9>38.0
Incidence of AF (per 1000 person-years)*0.91 (0.30–1.52)2.47 (1.62–3.31)Q1 2.84 (1.98–3.71)Q1 3.50 (2.54–4.47)Q1
Clinical features
 Female, n (%)684 (71.8)568 (54.8)Q1 422 (43.5)Q1,Q2 376 (37.8)Q1,Q2,Q3
 Age (year)39.7±12.941.1±14.3Q1 43.5±15.9Q1,Q2 48.1±15.7Q1,Q2,Q3
 Body mass index (kg/m2)24.1±4.125.1±4.4Q1 25.9±4.4Q1,Q2 27.4±4.5Q1,Q2,Q3
  Daytime heart rate (bpm)77.8±10.778.1±10.978.5±10.978.5±11.0
Conventional blood pressure (mm Hg)†
 Systolic113.7±10.8119.6±12.0Q1 126.3±12.8Q1,Q2 140.2±17.0Q1,Q2,Q3
 Diastolic72.4±8.674.7±9.2Q1 77.7±9.6Q1,Q2 84.4±11.7Q1,Q2,Q3
 Mean86.1±8.289.7±9.2Q1 93.9±9.4Q1,Q2 103.0±12.0Q1,Q2,Q3
  Pulse pressure41.4±8.344.8±9.2Q1 48.6±11.0Q1,Q2 55.9±13.8Q1,Q2,Q3
Daytime blood pressure (mm Hg)
 Number of measurements/day32±7.031±6.9Q1 32±7.7Q2 32±7.7Q2
 Systolic113.0±5.5119.7±4.5Q1 127.0±3.9Q1,Q2 140.4±8.4Q1,Q2,Q3
 Diastolic71.4±5.574.6±5.4Q1 78.4±5.9Q1,Q2 85.3±8.1Q1,Q2,Q3
 Mean85.1±5.189.2±4.6Q1 94.2±4.8Q1,Q2 103.2±7.6Q1,Q2,Q3
  Pulse pressure41.7±4.945.1±5.3Q1 48.6±5.9Q1,Q2 55.1±8.2Q1,Q2,Q3
Questionnaire data
 Tobacco use, n (%)254 (26.7)262 (25.3)277 (28.5)300 (30.1)Q2
 Alcohol intake ≥5 g/day, n (%)193 (20.2)264 (25.5)Q1 298 (30.7)Q1,Q2 353 (35.4)Q1,Q2,Q3
 Hypertension, n (%)98 (10.3)167 (16.1)Q1 277 (28.5)Q1,Q2 598 (60.0)Q1,Q2,Q3
 Antihypertensive treatment, n (%)74 (7.8)108 (10.4)Q1 157 (16.2)Q1,Q2 261 (26.2)Q1,Q2,Q3
 Diabetes mellitus, n (%)10 (1.0)21 (2.0)30 (3.1)Q1 63 (6.3)Q1,Q2,Q3
 History of CV diseases, n (%)56 (5.9)69 (6.7)88 (9.1)Q1 107 (10.7)Q1,Q2
Biochemical data
 Serum total cholesterol (mmol/L)5.15±1.025.22±1.105.40±1.16Q1,Q2 5.59±1.15Q1,Q2,Q3
  • Values are arithmetic mean±SD or number of subjects (%).

  • *Incidence rates were standardised for sex and age by the direct method.

  • †Average of five blood pressure readings obtained at one home visit.

  • AF, atrial fibrillation; CV, cardiovascular, Q, quartile of daytime systolic pressure load; Q1, P<0.05 vs Q1; Q2, P<0.05 vs Q2; Q3, P<0.05 vs Q3.