Cardiorespiratory Fitness and Risk of Sudden Cardiac Death in Men and Women in the United States: A Prospective Evaluation From the Aerobics Center Longitudinal Study

Association between accelerometer-derived physical activity and incident cardiac arrest

AIMS

Studies on objectively measured physical activity (PA) have investigated acute cardiovascular outcomes but not cardiac arrest (CA). Our study aimed to investigate the dose-response relationship between accelerometer-measured PA and CA by intensity of PA.

METHODS AND RESULTS

This prospective cohort study included 98 893 UK Biobank participants whose PA data were measured using wrist-worn accelerometers. Total PA volume was measured using the average overall acceleration. Minutes per week of light PA (LPA), moderate PA (MPA), and vigorous PA (VPA) were recorded. The incident CA was identified using diagnostic codes linked to hospital encounters and death records. Cox proportional hazard models with restricted cubic splines were used to study the associations, including sex differences. During the follow-up period (median: 7.31 years; interquartile range: 6.78-7.82 years), 282 incident CAs (0.39 per 1000 person-years) occurred. Total PA was inversely related to CA risk. The CA risk decreased sharply until the time spent in MPA or VPA reached ∼360 min or 20 min per week, respectively, after which it was relatively flat. The LPA was not associated with CA risk. Subgroup analyses showed a more pronounced association between PA and a reduced risk of CA in women compared to men.

CONCLUSION

Accelerometer-measured PA, particularly MPA and VPA, was associated with a lower CA risk. Furthermore, a stronger association was observed in women than men.

A tool to assess fitness among adults in public health studies - Predictive validity of the FFB-Mot questionnaire

BACKGROUND

Fitness has important implications for physical activity behavior and is associated with various health-related outcomes. It can be assessed through a test battery or a self-reported questionnaire. One example is the FFB-Mot (Funktionsfragebogen Motorik; engl. functional fitness questionnaire) which consist of 28 items to assess four components of fitness in adults: cardiorespiratory fitness/ endurance, muscular strength, gross motor coordination, and flexibility. The aims of this manuscript were to (1) provide an English-version of the FFB-Mot questionnaire (developed from the German-version using translation and back-translation) to the international community of researchers in the areas of physical activity, fitness and health in adults, and (2) examine the predictive validity of the FFB-Mot questionnaire in a large sample of community-dwelling adults.

METHODS

We used data from a longitudinal study in Germany with four measurement waves over a period of 18 years, with samples ranging between 310 and 437 participants (1572 adults in total, mean ages 46-58 years). To assess predictive validity, we calculated Pearson correlations between FFB-Mot data collected in 1997 and external health-related criteria (i.e., subjective health status, physician-rated health status, back pain, physical complaints and physical activity in minutes per week) collected in 2002, 2010, and 2015, and separately for males and females.

RESULTS

We observed correlations between higher FFB-Mot scores with better subjective health status (in 2002: males, r = 0.25; females, r = 0.18; in 2010: males, r = 0.29; females, r = 0.28; in 2015: males, r = 0.40), and higher physical activity (in 2002: males, r = 0.24; females, r = 0.25; in 2010: males, r = 0.30; females, r = 0.38; in 2015: females, r = 0.27). Higher FFB-Mot scores were also correlated with lower back pain (in 2002: males, r = -0.23; females, r = -0.25; in 2010: females, r = -0.22), less physical complaints (in 2002: males, r = -0.36; females, r = -0.24), and better physician-rated health status (in 2002: males, r = -0.41; females, r = -0.29, 2010: males, r = -0.38; females, r = -0.44; in 2015: males, r = -0.47).

CONCLUSIONS

Our results suggest that the FFB-Mot to assess fitness in adults has predictive validity for health-related outcomes as indicated by significant correlations, albeit some effect sizes are small. The FFB-Mot may be used as one-time assessment of self-reported fitness, or for repeated testing to assess change of self-reported fitness over time and in different settings (e.g., public health research).

Type 2 diabetes and in-hospital sudden cardiac arrest in ST-elevation myocardial infarction in the US

Aims

We aimed to assess the impact of diabetes on sudden cardiac arrest (SCA) in US patients hospitalized for ST-elevation myocardial infarction (STEMI).

Methods

We used the National Inpatient Sample (2005-2017) data to identify adult patients with STEMI. The primary outcome was in-hospital SCA. Secondary outcomes included in-hospital mortality, ventricular tachycardia (VT), ventricular fibrillation (VF), cardiogenic shock (CS), acute renal failure (ARF), and the revascularization strategy in SCA patients.

Results

SCA significantly increased from 4% in 2005 to 7.6% in 2018 in diabetes patients and from 3% in 2005 to 4.6% in 2018 in non-diabetes ones (p < 0.001 for both). Further, diabetes was associated with an increased risk of SCA [aOR = 1.432 (1.336-1.707)]. In SCA patients with diabetes, the mean age (SD) decreased from 68 (13) to 66 (11) years old, and mortality decreased from 65.7% to 49.3% during the observation period (p < 0.001). Compared to non-diabetes patients, those with T2DM had a higher adjusted risk of mortality, ARF, and CS [aOR = 1.72 (1.62-1.83), 1.52 (1.43-1.63), 1.25 (1.17-1.33); respectively] but not VF or VT. Those patients were more likely to undergo revascularization with CABG [aOR = 1.197 (1.065-1.345)] but less likely to undergo PCI [aOR = 0.708 (0.664-0.754)].

Conclusion

Diabetes is associated with an increased risk of sudden cardiac arrest in ST-elevation myocardial infarction. It is also associated with a higher mortality risk in SCA patients. However, the recent temporal mortality trend in SCA patients shows a steady decline, irrespective of diabetes.

Initial Assessment of a Brief Health, Fitness, and Spirituality Survey for Epidemiological Research: A Pilot Study

Background

Not many population-based health studies include items to assess both fitness and spirituality concepts. Therefore, the purpose of this study was to examine initial data of a brief health, fitness, and spirituality survey for epidemiological research.

Methods

This first phase pilot study used data from N = 56 adults 18+ years of age via electronic questionnaire. Measures of general health, fitness, physical activity (PA), body mass index (BMI), religiosity, and happiness were assessed. Reliability analyses were employed for PA, religiosity, and happiness scales. Validity coefficients were computed to evaluate convergence between scale scores and related measures. Finally, difference in health was examined between different levels of fitness to evaluate known groups discrimination.

Results

Respondents were middle-aged (Mean = 50.5 yr, SD = 14.3), majority white (69.5%, SD = 6.2), with relatively low BMI (Mean = 25.3, SD = 5.3). All three scales showed internal consistency reliability of α = 0.93, α = 0.89, and KR-20 = 0.56 for religiosity, happiness, and PA, respectively. Furthermore, scores converged (ps < 0.05) between fitness and PA (r = 0.43), health (r = 0.66), BMI (r = -0.28), and happiness (r = 0.25). Finally, health scores were significantly greater for high fitness versus low fitness in both male (p < 0.001) and female (p = 0.015) populations.

Conclusion

Results from this study indicate that a brief health, fitness, and spirituality survey can reliably measure its intended traits. A single-item of self-assessed fitness in particular has promise for large scale epidemiological research.

FDG-PET/CT Assessment of the Cerebral Protective Effects of Hydrogen in Rabbits with Cardiac Arrest

BACKGROUND

Anatomical imaging methods and histological examinations have limited clinical value for early monitoring of brain function damage after cardiac arrest (CA) in vivo.

OBJECTIVE

We aimed to assess the cerebral protective effects of hydrogen in rabbits with CA by using fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT).

METHODS

Male rabbits were divided into the hydrogen-treated (n=6), control (n=6), and sham (n=3) groups. Maximum standardized uptake values (SUVmax) were measured by FDG-PET/CT at baseline and post-resuscitation. Blood Ubiquitin C-terminal hydrolase-L1 (UCH-L1) and neuron specific enolase (NSE) were measured before and after the operation. After surgical euthanasia, brain tissues were extracted for Nissl staining.

RESULTS

SUVmax values first decreased at 2 and 24 h after resuscitation before rising in the hydrogen-treated and control groups. SUVmax values in the frontal, occipital, and left temporal lobes and in the whole brain were significantly different between the hydrogen and control groups at 2 and 24 h post-resuscitation (P<0.05). The neurological deficit scores at 24 and 48 h were lower in the hydrogen-treated group (P<0.05). At 24 h, the serum UCH-L1 and NSE levels were increased in the hydrogen and control groups (P<0.05), but not in the sham group. At 48 and 72 h post-CA, the plasma UCH-L1 and NSE levels in the hydrogen and control groups gradually decreased. Neuronal damage was smaller in the hydrogen group compared with the control group at 72 h.

CONCLUSION

FDG-PET/CT could be used to monitor early cerebral damage, indicating a novel method for evaluating the protective effects of hydrogen on the brain after CA.

Assessment of Cardiorespiratory and Metabolic Responses in Women with Obesity After Surgically Induced Weight Loss: Results from a Pilot Study

PURPOSE

Bariatric surgery is effective in controlling severe obesity. However, studies investigating the impact of surgically induced weight loss on cardiorespiratory and metabolic responses during maximal effort are controversial. The aim of this study was to assess cardiorespiratory and metabolic responses in women with obesity after bariatric surgery.

MATERIALS AND METHODS

We performed a secondary analysis on data from a pilot study with women with obesity submitted to bariatric surgery and who did not participate in a controlled physical training program. Anthropometry, pulmonary function (spirometry), and cardiorespiratory fitness (cardiopulmonary exercise testing [CPX]) were assessed before and after bariatric surgery.

RESULTS

Thirty-four women were included (38.7 ± 9.6 years, body mass index = 44.1 ± 6.3 kg/m²). Postoperative assessment was conducted 9.4 ± 2.7 months after surgery. After surgery, we observed a reduction in all anthropometric measurements (mean loss of 28.6 kg, p < 0.001), and improvement in spirometry values (p < 0.001). Relative VO_2peak (mL/kg/min) increased slightly (Δ = 1.7; p = 0.06); however, absolute VO_2peak (L/min) reduced significantly (Δ =  - 0.398; p < 0.001). We also observed an increase of 1.3 min (p < 0.001) in CPX duration, a reduction of 11.3 bpm (p < 0.001) in resting heart rate, and a decrease of systolic (p = 0.02) and diastolic (p < 0.001) blood pressures at peak effort.

CONCLUSION

Surgically induced weight loss without exercise training improved cardiac reserve, ventilatory response, blood pressure, and resting heart rate. Cardiorespiratory fitness reflected by relative VO_2peak increased slightly, despite increased tolerance to CPX.

Cardiorespiratory optimal point during exercise testing and sudden cardiac death: A prospective cohort study

BACKGROUND

Cardiorespiratory optimal point (COP) during exercise, a potentially useful submaximal cardiopulmonary exercise testing (CPET) variable, may be an independent risk factor for cardiovascular disease outcomes. However, the relationship of COP with risk of sudden cardiac death (SCD) has not been previously investigated. We sought to evaluate the association between COP during exercise and SCD risk and determine whether COP improves SCD risk prediction.

METHODS

COP, the minimum value of the ventilatory equivalent for oxygen (VE/VO2) in a given minute of a CPET, was ascertained in 2190 men who underwent clinical exercise testing. Hazard ratios (HRs) (95% confidence intervals [CIs]) and measures of risk discrimination for SCD were calculated.

RESULTS

A total of 240 SCDs death occurred during a median follow-up of 28.8 years. COP was linearly associated with SCD in a dose-response manner. In a multivariable model comprising several established and emerging CVD risk factors, the HR (95% CI) for SCD was 2.51 (1.36-4.62) per standard deviation increase in COP. This was minimally attenuated to 2.36 (1.27-4.37) on further adjustment for high sensitivity C-reactive protein. The association did not vary importantly in several relevant clinical subgroups. Addition of COP to a SCD risk score was associated with a C-index change of 0.0086 (0.0005 to 0.0167; p = .038) and difference in -2 log likelihood (p = .017).

CONCLUSIONS

COP during exercise is strongly, inversely and independently associated with SCD in a graded fashion. COP during exercise may potentially be used for the prediction of the long-term risk for SCD beyond established CVD risk factors.

Percentage of age-predicted cardiorespiratory fitness and risk of sudden cardiac death: A prospective cohort study

BACKGROUND

The inverse associations between cardiorespiratory fitness (CRF) and vascular outcomes have been established. However, there has been no prospective evaluation of the relationship between percentage of age-predicted cardiorespiratory fitness (%age-predicted CRF) and risk of sudden cardiac death (SCD).

OBJECTIVE

The purpose of this study was to assess the association of %age-predicted CRF with SCD risk in a long-term prospective cohort study.

METHODS

CRF was assessed using the gold standard respiratory gas exchange analyzer in 2276 men who underwent cardiopulmonary exercise testing. The age-predicted CRF estimated from a regression equation for age was converted to %age-predicted CRF using (Achieved CRF/Age-predicted CRF) × 100. Hazard ratios (HRs) [95% confidence intervals (CIs)] were calculated for SCD.

RESULTS

During median follow-up of 28.2 years, 260 SCDs occurred. There was a dose-response relationship between age-predicted CRF and SCD. A 1-SD increase in %age-predicted CRF was associated with a decreased risk of SCD in analysis adjusted for established risk factors (HR 0.60; 95% CI 0.53-0.70), which remained consistent on further adjustment for several potential confounders, including alcohol consumption, physical activity, socioeconomic status, and systemic inflammation (HR 0.73; 95% CI 0.62-0.85). The corresponding adjusted HRs were 0.34 (0.23-0.50) and 0.52 (0.34-0.79), respectively, when comparing extreme quartiles of %age-predicted CRF levels. HRs for the associations of absolute CRF levels with SCD risk in the same participants were similar.

CONCLUSION

Percentage of age-predicted CRF is continuously, strongly, and independently associated with risk of SCD and is comparable to absolute CRF as a risk indicator for SCD.

Effects of 2 Models of Aquatic Exercise Training on Cardiorespiratory Responses of Patients With Type 2 Diabetes: The Diabetes and Aquatic Training Study-A Randomized Controlled Trial

BACKGROUND

There are a lack of clinical trials with suitable methodological quality that compare aquatic exercise training types in type 2 diabetes (T2D) treatment. This study aimed to compare the effects of aerobic and combined aquatic training on cardiorespiratory outcomes in patients with T2D.

METHODS

Untrained patients with T2D were randomized to receive an aerobic aquatic training, a combined aquatic training, or a procedure control in 3 weekly sessions for 15 weeks. The sessions were 50 minutes long. The intensities were from 85% to 100% of heart rate of anaerobic threshold and at maximal velocity for aerobic and resistance parts, respectively. Resting heart rate, peak oxygen uptake (VO2peak), and oxygen uptake corresponding to second ventilatory threshold and its relation with VO2peak were evaluated.

RESULTS

Participants were 59.0 (8.2) years old and 51% women. Intervention groups increased in VO2peak (aerobic aquatic training group: 4.48 mL·kg-1·min-1, P = .004; combined aquatic training group: 5.27 mL·kg-1·min-1; P = .006) and oxygen uptake corresponding to second ventilatory threshold, whereas the control group presented an increase in oxygen uptake corresponding to second ventilatory threshold and minimal change in VO2peak.

CONCLUSIONS

Aerobic and combined aquatic exercise interventions improve the cardiorespiratory fitness of patients with T2D.

Physical activity and the risk of sudden cardiac death: a systematic review and meta-analysis of prospective studies

Background

Physical activity has been associated with a significant reduction in risk of sudden cardiac death in epidemiological studies, however, the strength of the association needs clarification. We conducted a systematic review and meta-analysis to summarize the available data from population-based prospective studies.

Methods

PubMed and Embase databases were searched for studies of physical activity and sudden cardiac death from inception to March 26th 2019. Prospective studies reporting adjusted relative risk (RR) estimates and 95% confidence intervals (CIs) of sudden cardiac death associated with physical activity were included. A random effects model was used to estimate summary RRs (95% CIs).

Results

Thirteen prospective studies were included in the systematic review. Eight prospective studies with 1193 sudden cardiac deaths among 136,298 participants were included in the meta-analysis of physical activity and sudden cardiac death and the summary RR for highest vs. lowest level of physical activity was 0.52 (95% CI: 0.45–0.60, I² = 0%, p_{heterogeneity} = 0.72). The association was similar in men and women and among American and European studies. In the dose-response analysis the summary RR was 0.68 (95% CI: 0.55–0.86, I² = 44%, n = 3) per 20 MET-hours/week. Although the test for nonlinearity was not significant, p_nonlinearity = 0.18, there was no further reduction in risk beyond 20–25 MET-hours/week. The summary RR was 0.58 (95% CI: 0.41–0.81, I² = 0%, p_{heterogeneity} = 0.65, n = 2) for the highest vs. the lowest level of cardiorespiratory fitness.

Conclusion

This meta-analysis suggest that a high compared to a low level of physical activity may reduce the risk of sudden cardiac death in the general population. Further studies are needed to clarify the dose-response relationship between specific subtypes and intensities of physical activity in relation to sudden cardiac death.

Effect of acupuncture in physiological parameters and endurance running performance

BACKGROUND

Few studies have examined the effect of acupuncture (AC) treatment in aerobic capacity and endurance performance in healthy adults. Thus, the aim of the present study was to evaluate the effects of AC on selected physiological parameters and 3 km running performance.

METHODS

Twenty-four healthy subjects with low to moderate aerobic capacity participated in the study and randomly assigned in two groups: AC group (ACG - N.=14) and control group (CG - N.=10). The subjects completed an incremental test to exhaustion and a 3 km race on a treadmill to evaluate their physiological responses and endurance running performance respectively, prior and after 4 weeks (8 sessions, twice a week) of acupuncture treatment.

RESULTS

AC treatment had a significant main effect in T3km [F(1, 21)=7.173, P=0.014, partial η2=0.255], as well as in VT [F(1, 21)=8.476, P=0.008, partial η2=0.288] and HRmax@3km [F(1, 21)=4.930, P=0.038, partial η2=0.190], after controlling for the effect of the pre-test, while no other significant main effects were detected.

CONCLUSIONS

Healthy physically active adults significantly improved their endurance running performance after 4 weeks of AC treatment. This is mainly due to the enhancement of the speed corresponding with VT, comparing with their baseline values.

Association between heart rate variability indices and features of spontaneous ventricular tachyarrhythmias in mice

Direct evidence is limited for the association between heart rate variability (HRV) indices and ventricular tachyarrhythmias (VTAs). While galectin-3 (Gal-3) is regarded as a causal factor for cardiac remodelling and a biomarker for arrhythmias, its regulation on VTAs and HVR is unknown. Using aged transgenic (TG) mice with cardiac overexpression of β₂ -adrenoceptors and spontaneous VTAs, we studied whether changes in HRV indices correlated with the severity of VTAs, and whether Gal-3 gene knockout (KO) in TG mice might limit VTA. Body-surface ECG was recorded (10-minute period) in 9- to 10-month-old mice of non-transgenic (nTG), TG and TG × Gal-3 knockout (TG/KO). Time-domain, frequency-domain and nonlinear-domain HRV indices were calculated using the R-R intervals extracted from ECG signals and compared with frequency of VTAs. TG and TG/KO mice developed frequent VTAs and showed significant changes in certain time-domain and nonlinear-domain HRV indices relative to nTG mice. The severity of VTAs in TG and TG/KO mice in combination, estimated by VTA counts and arrhythmia score, was significantly correlated with certain time-domain and nonlinear-domain HRV indices. In conclusion, significant changes in HRV indices were evident and correlated with the severity of spontaneous VTAs in TG mice. The frequency of VTA and HRV indices were largely comparable between TG and TG/KO mice. Deletion of Gal-3 in TG mice altered certain HRV indices implying influence by neuronally localized Gal-3 on autonomic nervous activity.

Nordic walking training in elderly, a randomized clinical trial. Part II: Biomechanical and metabolic adaptations

Background

Nordic walking is an attractive method of endurance training. Nevertheless, the biomechanic response due to the additional contribution of using poles in relation to free walking training has been less explored in the elderly. Purpose: This randomized parallel controlled trial aimed to assess the effects of 8 weeks of Nordic walking and free walking training on the walking economy, mechanical work, metabolically optimal speed, and electromyographic activation in elderly.

Methods

Thirty-three sedentary elderly were randomized into Nordic walking (n = 16) and free walking group (n = 17) with equalized loads. Submaximal walking tests were performed from 1 to 5 km h⁻¹ on the treadmill.

Results

Walking economy was improved in both free and Nordic walking groups (x² 4.91, p = 0.014) and the metabolically optimal speed was increased by approximately 0.5 km h⁻¹ changing the speed-cost profile. The electromyographic activation in lower and upper limbs, pendular recovery, and total, external, and internal mechanical work remained unchanged (p > 0.05). Interestingly, the internal mechanical work associated with arm movement was higher in the Nordic walking group than in the free walking group after training, while the co-contraction from upper limb muscles was reduced similarly to both groups.

Conclusions

Eight weeks of Nordic walking training effectively improved the walking economy and functionality as well as maintained the gait mechanics, similar to free walking training in elderly people. This enhancement in the metabolic economy may have been mediated by a reduction in the co-contraction from upper limb muscles.

Trial registration

ClinicalTrails.gov NCT03096964

Cardiorespiratory fitness and heart rate recovery predict sudden cardiac death independent of ejection fraction

OBJECTIVE

To evaluate whether cardiorespiratory fitness (CRF) and heart rate recovery (HRR) associate with the risk of sudden cardiac death (SCD) independently of left ventricular ejection fraction (LVEF).

METHODS

The Finnish Cardiovascular Study is a prospective clinical study of patients referred to clinical exercise testing in 2001-2008 and follow-up until December 2013. Patients without pacemakers undergoing first maximal or submaximal exercise testing with cycle ergometer were included (n=3776). CRF in metabolic equivalents (METs) was estimated by achieving maximal work level. HRR was defined as the reduction in heart rate 1 min after maximal exertion. Adjudication of SCD was based on death certificates. LVEF was measured for clinical indications in 71.4% of the patients (n=2697).

RESULTS

Population mean age was 55.7 years (SD 13.1; 61% men). 98 SCDs were recorded during a median follow-up of 9.1 years (6.9-10.7). Mean CRF and HRR were 7.7 (SD 2.9) METs and 25 (SD 12) beats/min/min. Both CRF and HRR were associated with the risk of SCD in the entire study population (HR_CRF0.47 (0.37-0.59), p<0.001 and HR_HRR0.57 (0.48-0.67), p<0.001 with HR estimates corresponding to one SD increase in the exposure variables) and with CRF, HRR and LVEF in the same model (HR_CRF0.60 (0.45-0.79), p<0.001, HR_HRR0.65 (0.51-0.82), p<0.001) or adjusting additionally for all significant risk factors for SCD (LVEF, sex, creatinine level, history of myocardial infarction and atrial fibrillation, corrected QT interval) (HR_CRF0.69 (0.52-0.93), p<0.01, HR_HRR0.74 (0.58-0.95) p=0.02).

CONCLUSIONS

CRF and HRR are significantly associated with the risk of SCD regardless of LVEF.

Is sauna bathing protective of sudden cardiac death? A review of the evidence

Sudden cardiac death (SCD) is a global public health burden accounting for 15-20% of all deaths. Though established atherosclerotic risk factors explain a large proportion of the risk of SCD, these factors are often absent in a large proportion of SCD victims and the pathogenesis of SCD is still not fully established. It therefore appears that additional factors may be involved. Sauna bathing is a traditional Finnish activity that is mainly used for the purposes of relaxation and pleasure. Beyond its use for these purposes, sauna bathing has been linked with several health benefits. Emerging evidence suggests that sauna bathing is associated with reduced risk of adverse cardiovascular (CV) disease (CVD) and non-CVD outcomes as well as mortality. A number of reports have linked sauna bathing with reduced or increased risk of SCD, but the evidence is uncertain. This review summarizes available studies linking sauna bathing with SCD, the postulated mechanistic pathways underlying these associations, outlines areas of outstanding uncertainty, and the implications for prevention. We employed a comprehensive search for observational studies, randomized controlled trials (RCTs), and non-RCTs from MEDLINE and Embase since their inception until March 2019. Observational data suggest that regular sauna bathing is associated with a substantial risk reduction in SCD. Furthermore, the data suggest that a combination of regular physical activity and sauna baths confers substantial risk reduction for SCD compared with either modality alone. Few reports have linked sauna baths with SCDs, but these single case incidents have been attributed to the effects of dehydration, hypotension, and cardiac arrhythmias due to a combination of sauna exposure and alcohol consumption. Sauna bathing is generally safe for most healthy people and even among patients with stable CVD, if used sensibly and with caution. Plausible pathways underlying the protective effect of sauna bathing on SCD may be linked to the impact on CV function via reduced arterial stiffness, decreases in inflammation and oxidative stress, stabilization of the autonomic nervous system, beneficial changes in circulating lipid profiles and other CVD risk markers, and lowering of systemic blood pressure. Sauna is a potential novel tool to promote SCD prevention in addition to other known means, being an enjoyable way to take care of general health and well-being.

The role of cardiorespiratory fitness on the risk of sudden cardiac death at the population level: A systematic review and meta-analysis of the available evidence

Cardiorespiratory fitness (CRF) has been widely studied as a powerful and independent predictor of all-cause and disease-specific mortality. Sudden cardiac death (SCD) is recognized as a significant cause of mortality among the general population, including the general population without previous symptoms of any coronary heart disease (CHD). Consequently, SCD is an important public health problem, which constitutes a clinical challenge. Thus, prevention of SCD by detecting early risk factors could be a useful tool, contributing to the American Heart Association's goal of decreasing the incidence of SCD at the population level. The identification of these risk factors for CVD would facilitate the large-scale screening of those participants at higher risk of SCD. This systematic review collects information about the role of CRF on the risk of SCD at the available evidence, and analyzes the long-term influence of CRF as a risk factor and independent predictor of SCD.

Cardiorespiratory Fitness and the Risk of Serious Ventricular Arrhythmias: A Prospective Cohort Study

Cardiorespiratory fitness (CRF) is an established risk factor for cardiovascular disease outcomes. However, the relationship of CRF with risk of ventricular arrhythmias (VAs) is unknown. We aimed to assess the prospective association of CRF with the risk of serious VAs. Cardiorespiratory fitness, as measured by maximal oxygen uptake, was assessed using a respiratory gas exchange analyzer in 2299 middle-aged men in the Kuopio Ischemic Heart Disease prospective cohort. We corrected for within-person variability in CRF levels using data from repeated measurements 11 years apart. During median follow-up of 25.3 years (interquartile range, 18.7-27.2 years), 73 serious VAs were recorded. The age-adjusted regression dilution ratio of CRF was 0.58 (95% CI, 0.53-0.64). In analysis adjusted for age, the hazard ratio (HR) for serious VAs per 1-SD increase in CRF was 0.64 (95% CI, 0.49-0.84). The association persisted on additional adjustment for body mass index, systolic blood pressure, history of hypertension, prevalent coronary heart disease, smoking, history of diabetes, cholesterol level, alcohol consumption, and physical activity (HR, 0.67; 95% CI, 0.51-0.88). The corresponding adjusted HRs (95% CIs) were 0.29 (0.14-0.59) and 0.32 (0.15-0.65), respectively, comparing the top vs bottom tertiles. The associations were stronger on correction for regression dilution bias, remained consistent on exclusion of men with a history of coronary heart disease, and did not vary importantly in several relevant clinical subgroups. Cardiorespiratory fitness is inversely associated with future risk of serious VAs, independently of several cardiovascular disease risk factors. Further research is needed to assess the causal relevance of these findings.

Cardiorespiratory fitness and cardiovascular disease - The past, present, and future

The importance of cardiorespiratory fitness (CRF) is now well established and it is increasingly being recognized as an essential variable which should be assessed in health screenings. The key findings that have established the clinical significance of CRF are reviewed in this report, along with an overview of the current relevance of exercise as a form of medicine that can provide a number of positive health outcomes, including increasing CRF. Current assessment options for assessing CRF are also reviewed, including the direct measurement via cardiopulmonary exercise testing which now can be interpreted with age and sex-specific reference values. Future directions for the use of CRF and related measures are presented.

An Update on the Role of Cardiorespiratory Fitness, Structured Exercise and Lifestyle Physical Activity in Preventing Cardiovascular Disease and Health Risk

The cardiovascular disease (CVD) pandemic has placed considerable strain on healthcare systems, quality of life, and physical function, while remaining the leading cause of death globally. Decades of scientific investigations have fortified the protective effects of cardiorespiratory fitness (CRF), exercise training, and physical activity (PA) against the development of CVD. This review will summarize recent efforts that have made significant strides in; 1) the application of novel analytic techniques to increase the predictive utility of CRF; 2) understanding the protective effects of long-term compliance to PA recommendations through large cohort studies with multiple points of assessment; 3) and understanding the potential harms associated with extreme volumes of PA.

Effect of Cardiorespiratory Fitness on Risk of Sudden Cardiac Death in Overweight/Obese Men Aged 42 to 60 Years

The purpose of this study was to examine the subject and combined associations of cardiorespiratory fitness (fitness) and body mass index (BMI) with the risk of sudden cardiac death (SCD) in middle-aged men. This prospective study was based on a population sample of 2,357 men aged 42 to 60 years, who were followed up in the Kuopio Ischemic Heart Disease cohort study. Fitness was directly measured by peak oxygen uptake (VO_2peak) during progressive exercise testing to volitional fatigue. Participants were divided into 4 groups (fit-normal weight, unfit-normal weight, fit-overweight/obese, and unfit-overweight/obese) based on the median values of fitness and BMI. A total of 253 (10.7%) SCDs occurred during an average follow-up of 22 years. After adjusting for potential confounders, the hazard ratio (HR) and 95% confidence interval (CI) for SCD was 1.80 (95% CI 1.21 to 2.68) for BMI ≥30.0 kg/m² versus normal weight cohort, that is, BMI corresponding to 18.5 to 24.9 kg/m². However, these associations were no longer statistically significant after adjusting for VO_2peak (1.49, 95% CI 0.98 to 2.24). Compared with the lower levels of fitness, upper levels of fitness had a 39% lower risk of SCD (HR 0.61, 95% CI 0.40 to 0.92) after adjusting for potential confounders, including BMI. In the combined associations of fitness and BMI with the risk of SCD, unfit-overweight/obese men had 1.80 times (95% CI 1.06 to 3.06) increased risk of SCD, but fit-overweight/obese men were not at increased risk of SCD (HR 1.22, 95% CI 0.66 to 2.25) as compared with their fit-normal weight counterparts. In conclusion, both overweight/obesity and fitness were independently associated with the risk of SCD; however, fitness appears to attenuate the risk of SCD in overweight/obese men, suggesting that improving fitness may reduce the risk of SCD in this population.

Exercise capacity and clinical outcomes in adults followed in the Cooperative Study of Sickle Cell Disease (CSSCD)

OBJECTIVES

To determine the factors associated with exercise capacity in adults with sickle cell disease (SCD) and its relationship to hospitalizations and mortality.

METHODS

A total of 223 participants in the Cooperative Study of Sickle Cell Disease (CSSCD) (64% female, 70% hemoglobin SS/Sβ⁰ thalassemia, mean age 43.3 ± 7.5 years) underwent maximal exercise testing using a treadmill protocol with a mean duration of 11.6 ± 5.2 minutes.

RESULTS

Female sex (β = -3.34, 95% CI [-1.80, -4.88], P < 0.001), older age (β = -0.14, 95% CI [-0.24, -0.04], P = 0.005), higher body mass index (β = -0.23, 95% CI [-0.37, -0.10]; P = 0.001), and lower hemoglobin (β = 0.56, 95% CI [0.08, 1.04], P = 0.02) were independently associated with lower fitness, while there was a trend with abnormal pulmonary function testing (β = -1.42, 95% CI [-2.92, 0.07]; P = 0.06). Lower percent-predicted forced expiratory volume in 1 second (FEV₁ ) was independently associated with lower fitness (β = 0.08, 95% CI [0.03, 0.13], P = 0.001). Genotype and hospitalization rates for pain and acute chest syndrome (ACS) prior to testing were not associated with exercise capacity. Baseline exercise capacity predicted neither future pain or ACS nor survival in our cohort. Adults with SCD tolerated maximal exercise testing.

CONCLUSIONS

Prospective studies are needed to further evaluate the impact of regular exercise and improved fitness on clinical outcomes and mortality in SCD.

Association Between Cardiorespiratory Fitness and Health Care Costs: The Veterans Exercise Testing Study

OBJECTIVE

To determine the association between cardiorespiratory fitness (CRF) and annual health care costs in Veterans.

PATIENTS AND METHODS

The sample included 9942 subjects (mean age, 59±11 years) undergoing a maximal exercise test for clinical reasons between January 2005 and December 2012. Cardiorespiratory fitness, expressed as a percentage of age-predicted peak metabolic equivalents (METs) achieved, was categorized in quartiles. Total and annualized health care costs, derived from the Veterans Administration Allocated Resource Center, were compared using multiple regression, controlling for demographic and clinical characteristics.

RESULTS

A gradient for reduced health care costs was observed as CRF increased, with subjects in the least-fit quartile having approximately $14,662 (P<.001) higher overall costs per patient per year compared with those in the fittest quartile, after controlling for potential confounding variables. Each 1-MET higher increment in fitness was associated with a $1592 annual reduction in health care costs (5.6% lower cost per MET), and each higher quartile of fitness was associated with a $4163 annual cost reduction per patient. The effect of CRF was more pronounced among subjects without cardiovascular disease (CVD), suggesting that the results were not driven by the possibility that less-fit individuals had greater CVD. Cost savings attributable to higher fitness were greatest in overweight and obese subjects, with lower savings observed among those individuals with a body mass index less than 25 kg/m². In a model including historical, clinical, and exercise test responses, heart failure was the strongest predictor of health care costs, followed by CRF (P<.01).

CONCLUSION

Low CRF is associated with higher health care costs. Efforts to improve CRF may not only improve health but also result in lower health care costs.

The Effect of Rurality on Out-of-Hospital Cardiac Arrest Resuscitation Incidence: An Exploratory Study of a National Registry Utilizing a Categorical Approach

PURPOSE

Variation in incidence is a universal feature of out-of-hospital cardiac arrest (OHCA). One potential source of variation is the rurality of the location where the OHCA incident occurs. While previous work has used a simple binary approach to define rurality, the purpose of this study was to use a categorical approach to quantify the impact of urban-rural classification on OHCA incidence in the Republic of Ireland.

METHODS

The observed versus expected ratio of OHCA incidence where resuscitation was attempted for the period January 1, 2012, to December 31, 2014, was calculated for each of the 3,408 electoral divisions (ED). EDs were then classified into 1 of 6 urban-rural classes. Multilevel modeling was used to test for variation in incidence ratios (IR) across the urban-rural classes.

FINDINGS

A total of 4,755 cases of adult OHCA, not witnessed by Emergency Medical Services, where resuscitation was attempted were included in the study. The number of EDs in each category was as follows: city (n = 477); town (n = 293); near village (n = 182); remote village (n = 84); near rural (n = 1,479); remote rural (n = 893). The IR per ED varied from 0 to 18.38 (EDs, n = 3,408). Multilevel modeling showed that 2.36% of variation in IR was due to urban-rural classification. This dropped to 0.45% when adjusted for ED deprivation score and median distance to an ambulance station. The addition of other explanatory variables did not improve the model.

CONCLUSION

OHCA variation in Ireland is limited and almost fully explained by area-level deprivation and proximity to ambulance stations.