Table 1.
Baseline characteristics by HRR index.
| All | High HRR index | Average HRR index | Low HRR index | p | |
|---|---|---|---|---|---|
| (n = 38,740) | (n = 9054) | (n = 19,575) | (n = 10,111) | ||
| Demographics | |||||
| Age at baseline (year) | 58.1 ± 8.0 | 55.7 ± 8.0 | 58.2 ± 8.0 | 60.0 ± 7.0 | <0.001 |
| Male | 47.3% | 42.9% | 46.7% | 52.6% | <0.001 |
| College attendance | 33.6% | 36.6% | 34.0% | 30.2% | <0.001 |
| Ethnic background (European) | 90.9% | 88.5% | 91.0% | 92.9% | <0.001 |
| Deprivation index (higher) | 49.5% | 50.0% | 48.7% | 50.4% | 0.007 |
| BMI and lifestyle | |||||
| BMI (kg/m2) | 27.5 ± 4.4 | 26.0 ± 3.9 | 27.5 ± 4.3 | 28.7 ± 5.0 | <0.001 |
| Alcohol (≥4 drinks/week) | 47.2% | 45.7% | 47.4% | 48.0% | 0.005 |
| Physical activity level (MET-min)a | 2719 ± 2688 | 2911 ± 2768 | 2712 ± 2685 | 2535 ± 2613 | <0.001 |
| Cardiovascular risk and comorbidity | |||||
| Morbidity burden (high) | 26.9% | 24.8% | 26.7% | 29.3% | <0.001 |
| CVD risk scoreb | 0.55 ± 0.80 | 0.35 ± 0.70 | 0.52 ± 0.80 | 0.77 ± 0.90 | <0.001 |
| Reaction time (ms) | 568 ± 121 | 560 ± 118 | 568 ± 120 | 575 ± 123 | <0.001 |
| HR-control drugsc | 13.9% | 8.9% | 13.2% | 19.7% | <0.001 |
| Exercise metrics | |||||
| Resting HR (bpm) | 71 ± 10 | 62 ± 8 | 71 ± 9 | 80 ± 12 | <0.001 |
| Peak exercise HR (bpm) | 111 ± 15 | 116 ± 15 | 111 ± 14 | 107 ± 16 | <0.001 |
| Recovery HR (bpm)d | 81 ± 13 | 71 ± 13 | 81 ± 13 | 89 ± 15 | <0.001 |
| Peak exercise METse | 3.4 ± 0.6 | 3.5 ± 0.6 | 3.4 ± 0.5 | 3.2 ± 0.6 | <0.001 |
| Response ratio | 1.6 ± 0.1 | 1.9 ± 0.2 | 1.6 ± 0.1 | 1.3 ± 0.1 | <0.001 |
| Recovery ratio | 1.4 ± 0.1 | 1.7 ± 0.2 | 1.4 ± 0.1 | 1.2 ± 0.1 | <0.001 |
| HRR index | 2.2 ± 0.1 | 3.1 ± 0.6 | 2.2 ± 0.2 | 1.6 ± 0.2 | <0.001 |
Note: UK Biobank participants selected for the exercise electrocardiogram characteristics at baseline expressed as mean ± SD or percentage of total for each quartile of HRR index for categorical variables.
Abbreviations: BMI = body mass index; bpm = beat per minute; CVD = cardiovascular disease; HR = heart rate; HRR = heart rate response/recovery; MET = metabolic equivalent of task.
Physical activity level: Summed MET minutes per week for all activities.
CVD risk score: Presence of hypertension, cholesterol, diabetes mellitus, smoking status, or ischemic heart disease.
HR controlling medications (beta-blockers and non-dihydropyridine calcium channel blockers).
HR at 1 min from cessation of exercise.
Maximal oxygen uptake during exercise as estimated from the age, height, weight, resting HR, sex, and the maximal HR of each participant.