Effect of aerobic exercise on cognition in younger adults: A randomized clinical trial

OBJECTIVE

To determine efficacy of aerobic exercise for cognitive function in younger healthy adults.

METHODS

In a randomized, parallel-group, observer-masked, community-based clinical trial, 132 cognitively normal individuals aged 20-67 with below median aerobic capacity were randomly assigned to one of two 6-month, 4-times-weekly conditions: aerobic exercise and stretching/toning. Efficacy measures included aerobic capacity; cognitive function in several domains (executive function, episodic memory, processing speed, language, and attention), everyday function, body mass index (BMI), and cortical thickness.

RESULTS

Aerobic capacity increased significantly (β = 2.718; p = 0.003), and BMI decreased significantly (β = -0.596; p = 0.013) in the aerobic exercise but not in the stretching/toning condition. Executive function improved significantly in the aerobic exercise condition; this effect was moderated by age (β = 0.018 SD/y; p = 0.028). At age 40, the executive function measure increased by 0.228 SD (95% confidence interval [CI] 0.007-0.448), and by 0.596 SD (95% CI 0.219-0.973) at age 60. Cortical thickness increased significantly in the aerobic exercise group in a left frontal region and did not interact with age. Controlling for age and baseline performance, individuals with at least one APOE ε4 allele showed less improvement in executive function with aerobic exercise (β = 0.5129, 95% CI 0.0381-0.988; p = 0.0346).

CONCLUSIONS

This randomized clinical trial demonstrates the efficacy of aerobic exercise for cognition in adults age 20-67. The effect of aerobic exercise on executive function was more pronounced as age increased, suggesting that it may mitigate age-related declines. Increased cortical thickness suggests that aerobic exercise contributes to brain health in individuals as young as age 20.

CLINICALTRIALSGOV IDENTIFIER

NCT01179958.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that for adults age 20-67 with below median aerobic capacity, aerobic exercise significantly improves executive function but not other measures of cognitive function.

Aerobic Exercise Training and Inducible Inflammation: Results of a Randomized Controlled Trial in Healthy, Young Adults

Background Consensus panels regularly recommend aerobic exercise for its health-promoting properties, due in part to presumed anti-inflammatory effects, but many studies show no such effect, possibly related to study differences in participants, interventions, inflammatory markers, and statistical approaches. This variability makes an unequivocal determination of the anti-inflammatory effects of aerobic training elusive. Methods and Results We conducted a randomized controlled trial of 12 weeks of aerobic exercise training or a wait list control condition followed by 4 weeks of sedentary deconditioning on lipopolysaccharide (0, 0.1, and 1.0 ng/mL)-inducible tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and on toll-like receptor 4 in 119 healthy, sedentary young adults. Aerobic capacity by cardiopulmonary exercise testing was measured at study entry (T1) and after training (T2) and deconditioning (T3). Despite a 15% increase in maximal oxygen consumption, there were no changes in inflammatory markers. Additional analyses revealed a differential longitudinal aerobic exercise training effect by lipopolysaccharide level in inducible TNF -α ( P=0.08) and IL-6 ( P=0.011), showing T1 to T2 increases rather than decreases in inducible (lipopolysaccharide 0.1, 1.0 versus 0.0 ng/mL) TNF- α (51% increase, P=0.041) and IL-6 (42% increase, P=0.11), and significant T2 to T3 decreases in inducible TNF- α (54% decrease, P=0.007) and IL-6 (55% decrease, P<0.001). There were no significant changes in either group at the 0.0 ng/mL lipopolysaccharide level for TNF- α or IL-6. Conclusions The failure to support the primary hypotheses and the unexpected post hoc findings of an exercise-training-induced proinflammatory response raise questions about whether and under what conditions exercise training has anti-inflammatory effects. Clinical Trial Registration URL : http://www.clinicaltrials.gov . Unique identifier: NCT 01335737.

Trait emotion regulation strategies and diurnal cortisol profiles in healthy adults

OBJECTIVE

Experimental studies have shown that 2 emotion regulation strategies-suppression and reappraisal-are associated with differential profiles of physiological activation in response to a stress test. The present study aims to add to those findings by investigating whether individual differences in trait emotion regulation strategies are associated with diurnal cortisol patterns in a naturalistic context.

METHOD

A sample of 46 men and women from the Midlife in the United States II (MIDUS II) study completed the Emotion Regulation Questionnaire (ERQ) and provided 4 salivary cortisol samples per day over 4 consecutive days. Trait reappraisal and suppression were tested as predictors of 3 cortisol parameters averaged across days: cortisol awakening response (CAR), diurnal cortisol slope (DCS), and area under the curve with respect to ground (AUCg).

RESULTS

Higher scores on the suppression scale were associated with more physiological activation, as indicated by steeper CAR and flatter DCS. Suppression was not associated with AUCg, and reappraisal was not predictive of any cortisol parameter.

CONCLUSIONS

Individual differences in suppression, but not reappraisal, were linked to greater cortisol activation in this naturalistic study. These preliminary results add to a growing body of findings that link suppression to adverse psychological and physiological profiles. (PsycINFO Database Record

The ModRey: An Episodic Memory Test for Nonclinical and Preclinical Populations

List learning tests are used in practice for diagnosis and in research to characterize episodic memory, but often suffer from ceiling effects in unimpaired individuals. We developed the Modified Rey Auditory Verbal Learning Test, or ModRey, an episodic memory test for use in normal and preclinical populations. We administered the ModRey to 230 healthy adults and to 86 of the same individuals 102 days later and examined psychometric properties and effects of demographic factors. Primary measures were normally distributed without evidence of ceiling effect. Differences between alternate forms were of very small magnitude and not significant. Test-retest reliability was good. Higher participant age and lower participant education was associated with poorer performance across most outcome measures. We conclude that the ModRey is appropriate for episodic memory characterization in normal populations and could be used as an outcome measure in studies involving preclinical populations.

Autonomic Regulation and Auditory Hallucinations in Individuals With Schizophrenia: An Experience Sampling Study

Auditory Hallucinations (AH) cause substantial suffering and dysfunction, yet remain poorly understood and modeled. Previous reports have linked AH to increases in negative emotions, suggesting a role for the autonomic nervous system (ANS) in underlying this link. Employing an Experience Sampling Method (ESM) approach, 40 individuals with schizophrenia completed a 36-hour ambulatory assessment of AH and cardiac autonomic regulation. Participants carried mobile electronic devices that prompted them to report 10 times/d the severity of their momentary AH, along with a Holter monitor that continuously recorded their cardiac autonomic regulation. The clocks of the devices and monitors were synchronized, allowing for high time-resolution temporal linking of the AH and concurrent autonomic data. Power spectral analysis was used to determine the relative vagal (parasympathetic) contribution to autonomic regulation during 5 minutes prior to each experience sample. The participants also completed interview-based measures of AH (SAPS; PSYRATS). The ESM-measured severity of AH was significantly correlated with the overall SAPS-indexed AH severity, along with the PSYRATS-indexed AH frequency, duration, loudness, degree of negative content, and associated distress. A mixed-effect regression model indicated that momentary increases in autonomic arousal, characterized by decreases in vagal input, significantly predicted increases in ESM-measured AH severity. Vagal input averaged over the 36-hour assessment displayed a small but significant inverse correlation with the SAPS-indexed AH. The results provide preliminary support for a link between ANS regulation and AH. The findings also underscore the highly dynamic nature of AH and the need to utilize high time-resolution methodologies to investigate AH.

Vagally-mediated heart rate variability and indices of well-being: Results of a nationally representative study

OBJECTIVE

High frequency (HF) heart rate variability (HRV) has long been accepted as an index of cardiac vagal control. Recent studies report relationships between HF-HRV and indices of positive and negative affect, personality traits and well-being but these studies generally are based on small and selective samples.

METHOD

These relationships were examined using data from 967 participants in the second Midlife in the U.S. (MIDUS II) study. Participants completed survey questionnaires on well-being and affect. HF-HRV was measured at rest. A hierarchical series of regression analyses examined relationships between these various indices and HF-HRV before and after adjustment for relevant demographic and biomedical factors.

RESULTS

Significant inverse relationships were found only between indices of negative affect and HF-HRV. Relationships between indices of psychological and hedonic well-being and positive affect failed to reach significance.

CONCLUSIONS

These findings raise questions about relationships between cardiac parasympathetic modulation, emotion regulation, and indices of well-being. (PsycINFO Database Record

Vagal Recovery From Cognitive Challenge Moderates Age-Related Deficits in Executive Functioning

Decline in executive functioning (EF) is a hallmark of cognitive aging. We have previously reported that faster vagal recovery from cognitive challenge is associated with better EF. This study examined the association between vagal recovery from cognitive challenge and age-related differences in EF among 817 participants in the Midlife in the U.S. study (aged 35-86). Cardiac vagal control was measured as high-frequency heart rate variability. Vagal recovery moderated the association between age and EF (β = .811, p = .004). Secondary analyses revealed that older participants (aged 65-86) with faster vagal recovery had superior EF compared to their peers who had slower vagal recovery. In contrast, among younger (aged 35-54) and middle-aged (aged 55-64) participants, vagal recovery was not associated with EF. We conclude that faster vagal recovery from cognitive challenge is associated with reduced deficits in EF among older, but not younger individuals.

Use of Active-Play Video Games to Enhance Aerobic Fitness in Schizophrenia: Feasibility, Safety, and Adherence

OBJECTIVE

Active-play video games have been used to enhance aerobic fitness in various clinical populations, but their use among individuals with schizophrenia has been limited.

METHODS

Feasibility, acceptability, safety, and adherence data were obtained for use of aerobic exercise (AE) equipment by 16 individuals with schizophrenia during a 12-week AE program consisting of three one-hour exercise sessions per week. Equipment included exercise video games for Xbox 360 with Kinect motion sensing devices and traditional exercise equipment.

RESULTS

Most participants (81%) completed the training, attending an average of 79% of sessions. The proportion of time spent playing Xbox (39%) exceeded time spent on any other type of equipment. When using Xbox, participants played 2.24±1.59 games per session and reported high acceptability and enjoyment ratings, with no adverse events.

CONCLUSIONS

Measures of feasibility, acceptability, adherence, and safety support the integration of active-play video games into AE training for people with schizophrenia.

Heart rate variability predicts levels of inflammatory markers: Evidence for the vagal anti-inflammatory pathway

Evidence from numerous animal models shows that vagal activity regulates inflammatory responses by decreasing cytokine release. Heart rate variability (HRV) is a reliable index of cardiac vagal regulation and should be inversely related to levels of inflammatory markers. Inflammation is also regulated by sympathetic inputs, but only one previous paper controlled for this. In a larger and more representative sample, we sought to replicate those results and examine potential sex differences in the relationship between HRV and inflammatory markers. Using data from the MIDUS II study, we analyzed the relationship between 6 inflammatory markers and both HF-HRV and LF-HRV. After controlling for sympathetic effects measured by urinary norepinephrine as well as a host of other factors, LF-HRV was found to be inversely associated with fibrinogen, CRP and IL-6, while HF-HRV was inversely associated with fibrinogen and CRP. We did not observe consistent sex differences. These results support the existence of the vagal anti-inflammatory pathway and suggest that it has similar effects in men and women.

Beat-to-beat heart rate and blood pressure variability and hypertensive disease in pregnancy

OBJECTIVE

The aim of this study is to determine the relationship between heart rate and/or blood pressure variability, measured at 28 weeks' gestation, and the incidence of pregnancy-induced hypertension or preeclampsia.

STUDY DESIGN

Secondary analysis of data from a prospectively enrolled cohort of 385 active military women in whom spectral analysis of continuous heart rate and variability was measured at 28 weeks' gestation. The primary outcome was the predictive value of spectral analysis of heart rate and blood pressure for hypertensive diseases of pregnancy.

RESULTS

High-frequency heart rate variability was reduced and low-frequency variability of systolic and diastolic blood pressure increased in women who would develop pregnancy-induced hypertension but not preeclampsia. Low-frequency variability of diastolic blood pressure remained a significant predictor of pregnancy-induced hypertension but not preeclampsia after adjustment for age, weight, and blood pressure in a multivariate model.

CONCLUSION

Early identification of pregnancy-induced hypertension can facilitate treatment to avoid maternal morbidity. Understanding the physiological underpinnings of the two very different diseases may lead to improved treatment and prevention. If proven effective in a broader population, the ability to differentiate pregnancy-induced hypertension from preeclampsia may reduce unnecessary iatrogenic interventions or inappropriate preterm delivery.

The Impact of Aerobic Exercise on Brain-Derived Neurotrophic Factor and Neurocognition in Individuals With Schizophrenia: A Single-Blind, Randomized Clinical Trial

Individuals with schizophrenia display substantial neurocognitive deficits for which available treatments offer only limited benefits. Yet, findings from studies of animals, clinical and nonclinical populations have linked neurocognitive improvements to increases in aerobic fitness (AF) via aerobic exercise training (AE). Such improvements have been attributed to up-regulation of brain-derived neurotrophic factor (BDNF). However, the impact of AE on neurocognition, and the putative role of BDNF, have not been investigated in schizophrenia. Employing a proof-of-concept, single-blind, randomized clinical trial design, 33 individuals with schizophrenia were randomized to receive standard psychiatric treatment (n = 17; "treatment as usual"; TAU) or attend a 12-week AE program (n = 16) utilizing active-play video games (Xbox 360 Kinect) and traditional AE equipment. Participants completed assessments of AF (indexed by VO2 peak ml/kg/min), neurocognition (MATRICS Consensus Cognitive Battery), and serum-BDNF before and after and 12-week period. Twenty-six participants (79%) completed the study. At follow-up, the AE participants improved their AF by 18.0% vs a -0.5% decline in the TAU group (P = .002) and improved their neurocognition by 15.1% vs -2.0% decline in the TAU group (P = .031). Hierarchical multiple regression analyses indicated that enhancement in AF and increases in BDNF predicted 25.4% and 14.6% of the neurocognitive improvement variance, respectively. The results indicate AE is effective in enhancing neurocognitive functioning in people with schizophrenia and provide preliminary support for the impact of AE-related BDNF up-regulation on neurocognition in this population. Poor AF represents a modifiable risk factor for neurocognitive dysfunction in schizophrenia for which AE training offer a safe, nonstigmatizing, and side-effect-free intervention.

Marital status, marital quality, and heart rate variability in the MIDUS cohort

Previous research has shown marital status and marital quality are consistent predictors of health outcomes, including cardiovascular disease and mortality. To better understand the relationship among marital status, marital quality, and cardiovascular health, we examined how marital status and marital quality were associated with an early indicator of deteriorating cardiovascular health, high-frequency heart rate variability (HF-HRV). This study uses data from the National Survey of Midlife in the United States (MIDUS) Biomarker Substudy (N = 907) to examine differences in HF-HRV by traditional marital status categories (married, divorced, widowed, and never married) as well as further differentiating between the continuously married and remarried. In addition, links were also examined between HF-HRV and changes in marital quality (marital satisfaction, support, strain) among individuals in long-term marriages. No significant differences in HF-HRV were observed between married persons and those widowed, divorced, and never married. However, continuously married individuals had higher HF-HRV than remarried adults. Increases in marital satisfaction and support over 10 years were associated with higher HF-HRV, whereas increased marital strain over 10 years was associated with lower HF-HRV. Higher HF-HRV among the continuously married compared with the remarried suggests that previous marital disruptions may have lasting effects on cardiovascular health or that there may be other differences between the remarried versus those who remain married to the same person. Associations between marital quality and HF-HRV suggest that variations in the quality of one's marriage may affect cardiovascular health.

Aerobic fitness and body mass index in individuals with schizophrenia: Implications for neurocognition and daily functioning

Previous reports indicate that among healthy individuals low aerobic fitness (AF) and high body-mass index (BMI) predict poor neurocognition and daily-functioning. It is unknown whether these associations extend to disorders characterized by poor neurocognition, such as schizophrenia. Therefore, we compared AF and BMI in individuals with schizophrenia and non-clinical controls, and then within the schizophrenia group we examined the links between AF, BMI, neurocognition and daily-functioning. Thirty-two individuals with schizophrenia and 64 gender- and age-matched controls completed assessments of AF (indexed by VO2max) and BMI. The former also completed measures of neurocognition, daily-functioning and physical activity. The schizophrenia group displayed significantly lower AF and higher BMI. In the schizophrenia group, AF was significantly correlated with overall neurocognition (r=0.57), along with executive functioning, working memory, social cognition, and processing speed. A hierarchical regression analysis indicated that AF accounted for 22% of the neurocognition variance. Furthermore, AF was significantly correlated with overall daily-functioning (r=0.46). In contrast, BMI displayed significant inverse correlations with neurocognition, but no associations to daily-functioning. AF was significantly correlated physical activity. The authors discuss the potential use of AF-enhancing interventions to improve neurocognitive and daily-functioning in schizophrenia, along with putative neurobiological mechanisms underlying these links, including Brain-Derived Neurotrophic Factor.

Quantifying serotonin transporters by PET with [11C]-DASB before and after interferon-α treatment

BACKGROUND

Interferon-α (IFN-α) therapy is frequently associated with disabling depression, fatigue, and related neuropsychiatric effects. Although depression in major depressive disorder is associated with low serotonin transporter binding, animal models suggest that IFN-associated mood effects are linked to increased presynaptic serotonin transporter binding. This study tested the hypotheses that IFN administration to human subjects increases presynaptic serotonin binding activity, and that this effect correlates with incident depression symptoms.

METHODS

Positron emission tomography (PET) scans using [11C]-DASB were obtained for nine hepatitis C patients before and after IFN-α treatment for 8 weeks. Serotonin transporter binding was estimated using the likelihood estimation in graphical analysis (LEGA) model and measured as the volume of distribution (VT) divided by the free fraction of ligand (fP). Depression was measured with the Structured Clinical Interview for DSM-IV Diagnosis (SCID) and the Hamilton Rating Scale for Depression (HAM-D).

RESULTS

Compared to pre-IFN treatment values, changes in serotonin transporter binding and depression symptoms were not significant. There was no correlation between changes in serotonin transporter binding and depression symptoms.

LIMITATIONS

The study is limited by small sample size, minimal effect on observed mood symptoms within the sample, and brief duration of follow-up.

CONCLUSION

These findings do not support the hypothesis of an IFN-induced change in serotonin transporter function as the cause of incident depressive symptoms in patients treated with IFN-α. Additional study of these possible relationships should be of longer duration and include more subjects with more pronounced changes in mood.

Race differences in age-trends of autonomic nervous system functioning

OBJECTIVE

The objective of this study was to consider race differences in age-trends of autonomic nervous system functioning, using a national data set with a broad age range.

METHODS

Measures of baseline heart rate variability (HRV) and HRV reactivity were derived from electrocardiograph (ECG) recordings taken at rest and during cognitive stress tasks. Age-trends in HRV and HRV reactivity were compared among 204 African Americans and 833 Whites ages 34 to 83 years (M = 53.7, SD = 11.4), before and after controlling for socioeconomic status (SES).

RESULTS

For HRV-reactivity, age-trends were steeper among African Americans and lower SES participants than Whites and higher SES participants. For baseline HRV, age-trends varied by SES but not race.

DISCUSSION

Results relating to HRV-reactivity (but not baseline HRV) were consistent with hypotheses suggesting that African Americans are exposed to higher levels of stress and experience accelerated declines in health across the life span. The relevance of the findings to research on social stress and health disparities is discussed.

Effects of aerobic conditioning on cardiovascular sympathetic response to and recovery from challenge

Exercise has widely documented cardioprotective effects, but the mechanisms behind these effects are still poorly understood. Here, we test the hypothesis that aerobic training lowers cardiovascular sympathetic responses to and speeds recovery from challenge. We conducted a randomized, controlled trial contrasting aerobic versus strength training on indices of cardiac (pre-ejection period, PEP) and vascular (low-frequency blood pressure variability, LF-BPV) sympathetic responses to and recovery from psychological and orthostatic challenge in 149 young, healthy, sedentary adults. Aerobic and strength training did not alter PEP or LF-BPV reactivity to or recovery from challenge. These findings, from a large randomized, controlled trial using an intent-to-treat design, show that moderate aerobic exercise training has no effect on PEP and LF-BPV reactivity to or recovery from psychological or orthostatic challenge. In healthy young adults, the cardioprotective effects of exercise training are unlikely to be mediated by changes in sympathetic activity.

Aerobic exercise and strength training effects on cardiovascular sympathetic function in healthy adults: a randomized controlled trial

OBJECTIVE

Exercise has widely documented cardioprotective effects, but the mechanisms underlying these effects are not entirely known. Previously, we demonstrated that aerobic but not strength training lowered resting heart rate and increased cardiac vagal regulation, changes that were reversed by sedentary deconditioning. Here, we focus on the sympathetic nervous system and test whether aerobic training lowers levels of cardiovascular sympathetic activity in rest and that deconditioning would reverse this effect.

METHODS

We conducted a randomized controlled trial contrasting the effects of aerobic (A) versus strength (S) training on indices of cardiac (preejection period, or PEP) and vascular (low-frequency blood pressure variability, or LF BPV) sympathetic regulation in 149 young, healthy, and sedentary adults. Participants were studied before and after conditioning, as well as after 4 weeks of sedentary deconditioning.

RESULTS

As previously reported, aerobic capacity increased in response to conditioning and decreased after deconditioning in the aerobic, but not the strength, training group. Contrary to prediction, there was no differential effect of training on either PEP (A: mean [SD] -0.83 [7.8] milliseconds versus S: 1.47 [6.69] milliseconds) or LF BPV (A: mean [SD] -0.09 [0.93] ln mm Hg(2) versus S: 0.06 [0.79] ln mm Hg(2)) (both p values > .05).

CONCLUSIONS

These findings, from a large randomized controlled trial using an intent-to-treat design, show that moderate aerobic exercise training has no effect on resting state cardiovascular indices of PEP and LF BPV. These results indicate that in healthy, young adults, the cardioprotective effects of exercise training are unlikely to be mediated by changes in resting sympathetic activity.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT00358137.

The association of cardiac vagal control and executive functioning--findings from the MIDUS study

Cardiac vagal control (CVC), an index of parasympathetic contribution to cardiac regulation, has been linked to enhanced executive functioning (EF). However, findings to date have been based on small or unique samples. Additionally, previous studies assessed the CVC-EF link only during rest or recovery period from a cognitive challenge, but not during both states. In the present study, data on 817 socioeconomically diverse participants were obtained from the Midlife Development in the United States (MIDUS) study. As part of this study, participants completed cognitive tests, including EF, along with laboratory-based measures of CVC during rest and following recovery from a cognitive challenge. Regression analyses adjusting for respiratory rate revealed no effect of CVC at rest or during recovery on a global index of EF. However, exploratory post-hoc analyses of the components of the global EF index revealed a significant association between faster vagal recovery and better attention-switching and response inhibition abilities, as indexed by faster reaction time to the mixed SGST. This association remained significant after controlling for demographic, clinical (BMI, diseases and medications altering cardiac autonomic functioning, etc.), and health behavior covariates (Beta = .148, p = .010). Our findings suggest that future studies may need to investigate the links of CVC to specific EF abilities, rather than global measures of EF. Additionally, our results highlight the importance of assessing CVC during both rest and recovery from a cognitive challenge. The authors discuss the putative neurobiological underpinning of this link, as well as suggestions for future basic and clinical research.