Physical activity in youth is determinant of cardiovascular health in adulthood

This editorial refers to ‘Long-term physical activity time-in-target range in young adults with cardiovascular events in later life’, by Z. Huang et al., https://doi.org/10.1093/eurjpc/zwad403.

The negative effects of an inactive lifestyle have been confirmed by numerous studies and their meta-analyses, showing high levels of sedentary behaviour to be unfavourably associated with important health outcomes in adults. Among others, results revealed a significant association with an increased risk of total mortality, cardiovascular (CV) mortality, a greater risk of Type 2 diabetes, and further cardiometabolic risk factors.^1–3 Insufficient physical activity (PA) is a global burden and is considered to be the fourth leading cause of death in the world. According to the WHO, more than 1.5 billion people worldwide are insufficiently physically active, and 3.2 million deaths per Year are due to physical inactivity.⁴ The WHO⁵ definition of insufficient PA is <150 min/week with at least moderate intensity.

The preventive influence of regular PA on overall mortality and CV mortality has been documented in several large cohort studies and confirmed by meta-analyses.^6–10 These investigations provide impressive evidence of an inverse relationship between the level of PA and the risk of premature death as well as the risk of developing and/or dying from CV disease (CVD) or coronary heart disease (CHD).^6–10

Thus, international guidelines emphasize the central role of PA in the prevention of CVD disease at the individual and population level.^5,11,12 Current recommendations for adults (18–64 Years) are 150 min/week of moderate-intensity aerobic endurance activities or 75 min/week of high-intensity aerobic endurance activities or an appropriate combination of moderate- and high-intensity aerobic endurance activities. Additional health effects are achieved if the amount of moderate aerobic endurance activity is increased to 300 or 150 min/week of intensive aerobic endurance activity.^5,12,13

The results of a meta-analysis (36 studies; n = 3 439 874; 179 393 events, 12.3 Years follow-up) revealed that an increase from inactivity to achieving the recommended level of PA (150 min of moderate-intensity aerobic activity per week) was associated with a 23% lower CVD mortality risk, a 17% lower CVD incidence, and a 26% lower Type 2 diabetes mellitus incidence.¹⁴ These results support the relevance of the current recommendations.

In recent Years, the results of older cohort studies have been confirmed. In addition, new study results broadened the knowledge concerning the application of new measurement and/or analysis methods, thus closing knowledge gaps and creating new insights; in particular, regarding more targeted measurement of intensity, volume, and sustainability as well as the impact of these factors on the preventive potential of PA.

In a large cohort study, Wang et al.¹⁵ analysed (n = 403 681; 42.8 ± 16.3 Years; 36 861 deaths; 10.1 Years follow-up) whether adherence to the international recommendations for moderate PA (MPA; 150–299 vs. 0 min/week) and vigorous PA (VPA; ≥ 75–149 vs. 0 min/week) is sufficient to reduce all-cause and/or CV mortality and whether a higher proportion of VPA can achieve an even better effect. The results showed comparable associations for all-cause mortality (MPA −17%; VPA −20%) and CV mortality (MPA −25%; VPA −21%) when the WHO recommendations for MPA and VPA were followed, respectively. For the same total activity, participants with a higher proportion of VPA to MPA had significantly lower all-cause mortality.

In a recently published large population-based cohort using device-based measures of PA (n = 88 412; 62 ± 8 Years; follow-up median 6.8 Years; 4068 CV events) Dempsey et al.¹⁶ investigated the influence of volume and intensity of PA and the interaction of these two factors on CV risk. The results showed that both a higher volume of PA and a greater proportion of this volume that is performed with at least moderate intensity are associated with lower rates of CVD. The results also demonstrated the particular importance of PA intensity for CVD risk reduction. They support the more general recommendation that a higher volume of PA at any intensity is beneficial, but also provide clear evidence that a higher volume and intensity of PA further increase its preventive effectiveness. In recent decades, PA, measured as steps per day, has attracted increasing scientific interest, in particular the question of whether a certain minimum number of steps per day is sufficient to achieve a preventive effect and whether it is possible to make scientifically sound recommendations in this regard.

A recently published meta-analysis¹⁷ analysed the results of 17 studies (n = 227 000) assessing the effect of PA, expressed as the number of steps per day, and its association with all-cause mortality and/or CV mortality. The results show an inverse relationship between daily step count and all-cause mortality and CV mortality, with more steps being better beyond the cut point of 3867 steps/day for all-cause mortality and only 2337 steps for CV mortality. The analysis showed that an increase of 1000 steps correlated with a significant 15% reduction in all-cause mortality, and an increase of 500 steps correlated with a 7% reduction in the risk of CV mortality. In addition, there was a significant difference between the age groups, with the mortality reduction in the older age group (≥60 Years) being most pronounced at 6000–10 000 steps (42.3%), compared with the younger age group (<60 Years) where the risk was lowest at 7000–13 000 steps (48.7%).

However, despite the extensive study results on the preventive significance of PA in CVD risk reduction, the international guidelines for PA^5,13 have identified important research gaps that are relevant to public health. There is still insufficient evidence to determine whether the association between PA and CVD events varies by age. This is particularly true for young adulthood. Epidemiological data show that 81% of young people worldwide are insufficiently physically active.¹⁸ On average, PA decreases significantly in young adulthood as people make the transition from school to university or daily work.¹⁹ The young adulthood is an important transitional phase that shapes PA behaviour for the rest of adulthood and represents a critical window of opportunity for intervention.¹⁹ However, little is known about how the annual transition from young to middle adulthood influences PA and its relationship to CVD events, particularly before the age of 60 Years. The optimal dose of PA, particularly in young adulthood, to prevent CVD events in later life remains unknown.

Within the framework of the Coronary Artery Risk Development in Young Adults (CARDIA) study, a multicentre, prospective longitudinal study, starting in young adulthood with an extensive 30 Years of follow-up, the analyses also focused on PA and its relationship with CVD over the long term. Nagata et al.²⁰ evaluated PA patterns from young adulthood to middle age and its relationship to premature CVD events in a cohort of young adults [n = 5114, 54% female, median age at baseline 25.0 Years (22–28 Years), follow-up 30 Years]. Results of nine repeated measurements (Years 0, 2, 5, 7, 10, 15, 20, 25, 30) of moderate and vigorous PA using questionnaires enabled the evaluation of the individual PA patterns from young adulthood to middle age. The results confirm those of previous studies¹⁹ and demonstrate a continuous reduction in PA from early adulthood to middle age. Furthermore, the results confirm significant relationship between PA levels at young adulthood and the risk of premature CVD events during follow-up time. Lower PA levels, in 18-Year-olds were associated with a higher risk of premature CHD (+14%), heart failure (+21%), stroke (+20%), and any CVD (+15%). In addition, each annual reduction in the total PA score was associated with a higher annual risk of heart failure (+7%), stroke (+6%), and CVD (+4%). In contrast, being physically active at age of 18 Years was associated with reduced onset of any CHD (−41–59%) and any CVD (−31–40%). In individuals who met the recommended activity levels at every annual examination, the authors found a significant association with risk reduction for the premature onset of CHD (−40%) and any CVD (−26%). The results emphasize that the transition from young adulthood to midlife is an important period for promoting PA.

The recently published study results by Huang et al.²¹ in EJPC add important new knowledge in this field. The authors aimed to evaluate the relationship between long-term PA time-in-target range (PA TTR) in young adults and CVD events in late life using the follow-up period of ≥15 Years. The primary outcome was the combined endpoints of CVD events (fatal and non-fatal CHD, heart failure hospitalization, stroke, transient ischaemic attack). The secondary outcomes were subclinical coronary atherosclerosis which included the coronary calcification (CAC) prevalence at Year 15 and CAC progression in the later follow-up. Coronary calcification was obtained by a computed tomographic scan.

The study analysed data from the CARDIA study. A sample of 2902 participants aged 18–30 Years at baseline was included in the presented analysis. At the time of analysis, the mean age was 40.3 ± 3.6 Years. The cohort was followed for a median of 18.9 Years for CVD events.

Physical activity was measured at each visit (Years 0, 2, 5, 7, 10, 15) using an interview-administered validated CARDIA Physical Activity History Questionnaire. The questionnaire covered 13 areas of PA of varying intensity over the past Year. Physical activity time-in-target range was defined as the percentage of time during which the PA volume was over 150 min of moderate-intensity activity per week according to the guideline recommendations.^5,13 Physical activity time-in-target range was estimated with linear interpolation, using at least three longitudinal measurements of PA during baseline up to Year 15. Participants were categorized into four groups according to PA TTR; TTR 0 ≤ TTR < 25% (n = 1028); TTR 25% ≤ TTR < 50% (n = 444); TTR 50% ≤ TTR < 75% (n = 424); and 75% ≤ TTR ≤ 100% (n = 1006). The percentage of TTR value indicated the time period of the PA level over 150 min of moderate-intensity activity per week over the 15 Years follow-up period.

The results revealed that the cumulative incidence of CVD events was lowest in the group with the highest TTR compared with other groups. A significant association was documented in the group with a PA TTR ≥ 75% showing 40% risk reduction [fully adjusted model: hazard ratio (HR): 0.60; 95% confidence interval (CI): 0.38–0.95; P = 0.030] compared with the lowest TTR group. The risk of CVD events was reduced by 21% per 1 − SD increase in PA TTR (HR: 0.79; 95% CI: 0.65–0.97; P = 0.023). Therefore, to maintain a significantly lower risk of CVD events into adulthood and to maximize CV benefits, it is important to comply with the guideline-recommended PA level of at least 75% PA TTR throughout young adulthood. Furthermore, for the primary outcome, a linear trend was observed after multivariable adjustment, i.e. that PA TTR at younger ages is inversely linearly associated with the risk of CVD events later in life.

The longer young adults adhere to the PA level recommended in the guidelines, the lower the risk of CVD events later in life.

The analysis of the secondary endpoints revealed no significant correlation with PA TTR. Thus, the results could not conform a relationship between the period in which the level of PA recommended in the guidelines is adhered to and the prevalence and progression of coronary calcification in later life. This could be due to the relatively young age of the cohort at the time of measurement and the relatively short follow-up period for the young age of the cohort. Hence, subsequent analyses of this study data after a longer observation period and in a larger cohort should be performed.

The use of TTR as a measure for monitoring long-term PA over time is a novel and interesting method, and the results support the usefulness of this method. None of the previous studies have presented long-term PA at the recommended activity level. In addition, in previous studies, the average age of the cohort studied was higher. The authors point out that this is at least one of the first larger cohort studies to examine PA TTR and its association with CVD events and subclinical coronary atherosclerosis in young adults. In this regard, the study provides novel results. To summarize, the results demonstrate the importance of regular and sufficient volume of PA in young adulthood and also confirm the important preventive role of PA in young adults.

In conclusion, it is evident how important PA is in young adulthood and certainly not only to reduce the risk of CV and cardiometabolic diseases. This group needs our attention. The focus of future research must pay greater attention to this target group and the importance of this life stage for prevention must be emphasized in future guidelines and recommendations. In addition, this knowledge has to be translated into nationwide prevention programmes to motivate and to convince the youth and their parents as well to implement regular and sufficient PA into daily life. It is time to act.

References

Author notes