Did 5 years of supervised training lower deaths after age 70?
Not shown: 4.5% vs 4.7% in active controls, HR 0.92 (0.58 to 1.47). The HIIT signal was exploratory and non-significant. Healthy, active sample.
Main caveat: Control contamination: controls exercised at an intensity between the other two groups, and they had the same health checks.
All Trondheim residents born 1936-1942 were invited (6966), and 1567 took part. Two of five weekly 30-minute guideline sessions were replaced by HIIT or by isocaloric moderate work; controls were asked to follow guidelines. No difference was shown for mortality, cardiovascular events or cancer events.
The authors still conclude their data suggest HIIT lowers the risk of premature death and that guidelines should require some high-intensity work; that is their reading of non-significant, exploratory contrasts. They also write that all three interventions reduced premature death, which this trial cannot test because no arm was left without activity advice.
Protocol
HIIT (n=400): 10-minute warm-up, then 4×4 minutes at about 90% of peak heart rate, twice weekly.
Moderate (n=387): 50 minutes at about 70% of peak heart rate, twice weekly.
Control (n=780): 30 minutes of moderate activity almost every day, unsupervised.
Supervision: spinning sessions every sixth week, with outdoor sessions offered twice weekly.
Power: planned to detect a fall in mortality from 10% to 5%, with 90% power.
Adjustment: sex, cohabitation and age. Adherence came from a questionnaire.
Funding: Research Council of Norway, K.G. Jebsen Foundation and public Norwegian health bodies, with no role in the study.
Key Results
| Outcome at 5 years | Control | Moderate | HIIT |
|---|---|---|---|
| All-cause deaths | 4.7% (37) | 5.9% (23) | 3.0% (12) |
| Adjusted HR vs control (95% CI) | 1.00 | 1.24 (0.73 to 2.10) | 0.63 (0.33 to 1.20) |
| Cardiovascular events | 16.0% (125) | 15.5% (60) | 15.5% (62) |
| Cancer events | 13.7% (107) | 11.9% (46) | 12.5% (50) |
| Acute myocardial infarction | 3.1% (24) | 1.3% (5) | 4% (16) |
| Followed the assigned programme at 5 years | 69% | 51% | 47% |
| Drop-outs at 5 years | 20% | 26% | 33% |
HIIT vs moderate: adjusted HR 0.51 (0.25 to 1.02); unadjusted 0.49 (0.25 to 0.99). The abstract gives only the adjusted figure, which crosses 1.
Crossover: 23%, 22% and 18% of controls had moved to HIIT at one, three and five years.
Peak oxygen uptake: HIIT was 0.7 mL/kg/min above control (P=0.02) and above moderate (P=0.04) at five years. Combined training against control was 0.8, 0.7 and 0.3 mL/kg/min higher at one, three and five years (the last P=0.17).
Safety: no cardiovascular events during supervised sessions; three fractures on slippery outdoor surfaces.
Myocardial infarction: 16 in HIIT against 5 in moderate, with 3.1% (24) in controls and no test in the main text. Crude Fisher p about 0.03 against moderate and 0.40 against control (our arithmetic), unplanned and among many outcomes: a signal to watch, not a finding.
Reporting: the combined atrial fibrillation row prints 7.5% (56), but 56/787 is 7.1% (our arithmetic). Text says 80% reported medium or high activity, while Table 1 gives 1390 of 1519, 92% (our arithmetic).
Mechanisms
Measured: peak oxygen uptake and quality of life. Physical and mental summary scores were higher with HIIT at five years.
Authors' interpretation: higher peak oxygen uptake after HIIT might have contributed to lower mortality.
Inference: a 0.7 mL/kg/min difference is small beside the 1-MET contrasts of REF-1560, so it is a thin basis for a mortality effect of this size.
Practical Application
Did 5 years of supervised training lower deaths after age 70? Not shown: 4.5% vs 4.7% in active controls, HR 0.92 (0.58 to 1.47). The HIIT signal was exploratory and non-significant. Healthy, active sample.
Good for: feasibility, and limited safety data. People in their seventies did 4×4 sessions for five years with no cardiovascular events in supervised sessions, the only ones monitored for events during exercise; about half kept to the protocol, and infarctions ran 16 vs 5 against moderate.
Good for: an honest limit: randomised evidence that assigning structured training rather than advice lowers mortality is missing, not refuted.
Not good for: saying "HIIT lowers death risk". The CI includes no effect and 12 deaths carry the arm.
Not good for: saying exercise does not matter. The CI allows a large benefit or harm, and the contrast is active against similarly active.
Limitations
Control contamination: controls exercised at an intensity between the other two groups, and they had the same health checks.
Healthy volunteers: control mortality was less than half the roughly 10% expected for older Norwegians, leaving the trial short of events.
Adherence and drop-out differed by arm and worsened with HIIT; adherence was self-reported.
Exploratory subgroup: the HIIT contrast has few deaths and no multiplicity control in view.
How this entry was checked and changed
Why this level
large registered RCT. This covers the primary comparison, against an active control. The HIIT contrasts are exploratory and carry no such weight