Brief bursts of activity linked to heart health benefits for women

By Vijay Kumar MalesuReviewed by Danielle Ellis, B.Sc.Dec 5 2024

A study reveals that just 3.4 minutes of daily vigorous intermittent lifestyle physical activity (VILPA) is associated with a 45% reduction in major adverse cardiovascular events and a 67% lower risk of heart failure in women

In a recent study published in the British Journal of Sports Medicine, a group of researchers explored sex differences in the dose–response relationship between vigorous intermittent lifestyle physical activity (VILPA) and major adverse cardiovascular events (MACE) in non-exercisers and exercisers from the United Kingdom (UK) Biobank.

Background

Cardiovascular disease (CVD) remains the leading global cause of death, with MACE representing key outcomes. While structured exercise sessions emphasizing longer physical activity bouts are well-studied, the cardiovascular benefits of shorter bouts of vigorous physical activity (VPA) remain unclear.

Vigorous intensity activities, though highly effective, are often impractical for middle-aged adults. Wearable devices now enable the measurement of brief, sporadic VILPA in daily routines. Given sex-specific differences in cardiovascular physiology and fitness, further research is needed to assess whether VILPA’s cardiovascular benefits vary by sex, informing tailored prevention strategies for CVD.

About the study

The UK Biobank is a prospective cohort study that recruited adults aged 40 to 69 years between 2006 and 2010. Ethical approval for the study was granted by the National Health Service (NHS) National Research Ethics Service, and all participants provided informed consent. Between 2013 and 2015, 103,684 participants wore wrist accelerometers for seven days to capture objective measures of physical activity.

Valid monitoring days required a wear time of at least 16 hours, and participants with at least three valid days, including one weekend day, were included in the analysis. Exclusions applied to individuals with insufficient wear time, missing covariates, or self-reported walking disabilities.

Participants were classified as non-exercisers if they reported no leisure-time exercise and no more than one recreational walk per week. For comparison, a subgroup of exercisers, defined as those engaging in leisure-time exercise or walking more than once weekly, was also analyzed. VILPA was assessed using a validated machine-learning-based activity classifier, focusing on short bouts lasting up to two minutes. Analyses standardized VILPA bouts to one minute for comparability and effect size interpretation.

MACE were identified using hospital records and death registries, including myocardial infarction, stroke, and heart failure. Fine-Gray subdistribution hazards accounted for competing non-CVD mortality risks. The study excluded participants with pre-existing CVD or events occurring within the first two years of follow-up to minimize reverse causation. Sensitivity analyses tested the accuracy of results, adjusting for potential mediators and alternative reference points for physical activity levels.

Study results

The final sample for analysis comprised 22,368 UK Biobank participants (13,018 women and 9,350 men), yielding 819 MACE during the follow-up period, with 331 events in women and 488 in men. Sub-analyses of myocardial infarction, heart failure, and stroke included slightly fewer participants due to event-specific exclusions. Stroke subtypes were analyzed separately, though the low incidence of hemorrhagic strokes limited the feasibility of comparisons. The censoring rate for the study was high (93.75%), with participants censored at the end of the follow-up period in November 2022 if no events occurred.

Participants had a mean age of 61.9 years, and the average follow-up was 7.9 years, totaling 176,678 person-years of observation. Sex-specific differences in baseline characteristics and daily VILPA duration were examined to assess potential confounding factors. Dose–response analyses revealed significant associations between daily VILPA duration and cardiovascular outcomes, with notable sex differences.

Women showed strong dose–response relationships for MACE, myocardial infarction, and heart failure, while associations in men were less pronounced. For example, the median daily VILPA duration of 3.4 minutes in women was associated with a hazard ratio (HR) of 0.55 for MACE, compared to 0.84 for men.

Daily VILPA frequency, both raw and length-standardized, demonstrated similar patterns, with women benefiting more substantially. The median frequency of length-standardized bouts (1.4 bouts per day in women) was associated with an HR of 0.56 for MACE. Minimum effective doses to achieve 50% of the optimal risk reduction were lower for women across all outcomes, with 1.6 minutes per day sufficient for MACE reduction compared to 2.3 minutes in men. Similar patterns were observed for myocardial infarction and heart failure, with statistically significant reductions in women only.

Comparisons with exercisers indicated that the range of VPA was broader than VILPA. Unlike non-exercisers, no significant sex differences in VPA dose–response associations were observed among exercisers for MACE, myocardial infarction, or heart failure, though a stroke association was seen in men.

Variations in the metabolic equivalents (MET) thresholds for vigorous intensity and other adjustments did not materially alter the results. Differences in relative intensity during VILPA bouts likely contributed to the observed sex-specific outcomes, as women exhibited higher relative physiological effort compared to men.

Conclusions

To summarize, this study highlights a significant, linear dose–response association between VILPA and cardiovascular outcomes in women, with less consistent findings in men. Women’s median VILPA duration of 3.4 minutes per day was linked to a 45% reduction in MACE risk, with minimum doses of ~1.5 minutes per day yielding substantial benefits. Higher relative VILPA intensity in women may explain these differences, though sensitivity analyses provide mixed support.