The authors examined the prospective relationship between physical activity and incident depression and explored potential moderators.
Prospective cohort studies evaluating incident depression were ...searched from database inception through Oct. 18, 2017, on PubMed, PsycINFO, Embase, and SPORTDiscus. Demographic and clinical data, data on physical activity and depression assessments, and odds ratios, relative risks, and hazard ratios with 95% confidence intervals were extracted. Random-effects meta-analyses were conducted, and the potential sources of heterogeneity were explored. Methodological quality was assessed using the Newcastle-Ottawa Scale.
A total of 49 unique prospective studies (N=266,939; median proportion of males across studies, 47%) were followed up for 1,837,794 person-years. Compared with people with low levels of physical activity, those with high levels had lower odds of developing depression (adjusted odds ratio=0.83, 95% CI=0.79, 0.88; I
=0.00). Furthermore, physical activity had a protective effect against the emergence of depression in youths (adjusted odds ratio=0.90, 95% CI=0.83, 0.98), in adults (adjusted odds ratio=0.78, 95% CI=0.70, 0.87), and in elderly persons (adjusted odds ratio=0.79, 95% CI=0.72, 0.86). Protective effects against depression were found across geographical regions, with adjusted odds ratios ranging from 0.65 to 0.84 in Asia, Europe, North America, and Oceania, and against increased incidence of positive screen for depressive symptoms (adjusted odds ratio=0.84, 95% CI=0.79, 0.89) or major depression diagnosis (adjusted odds ratio=0.86, 95% CI=0.75, 0.98). No moderators were identified. Results were consistent for unadjusted odds ratios and for adjusted and unadjusted relative risks/hazard ratios. Overall study quality was moderate to high (Newcastle-Ottawa Scale score, 6.3). Although significant publication bias was found, adjusting for this did not change the magnitude of the associations.
Available evidence supports the notion that physical activity can confer protection against the emergence of depression regardless of age and geographical region.
The relative contributions of genetic and environmental factors to variation in immune responses are poorly understood. Here, we performed a phenotypic analysis of immunological parameters in ...laboratory mice carrying susceptibility genes implicated in inflammatory bowel disease (IBD) (Nod2 and Atg16l1) upon exposure to environmental microbes. Mice were released into an outdoor enclosure (rewilded) and then profiled for immune responses in the blood and lymph nodes. Variations of immune cell populations were largely driven by the environment, whereas cytokine production elicited by microbial antigens was more affected by the genetic mutations. We identified transcriptional signatures in the lymph nodes associated with differences in T cell populations. Subnetworks associated with responses against Clostridium perfringens, Candida albicans, and Bacteroides vulgatus were also coupled with rewilding. Therefore, exposing laboratory mice with genetic mutations to a natural environment uncovers different contributions to variations in microbial responses and immune cell composition.
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•Immune and microbial phenotyping of lab and rewilded Nod2 and Atg16l1 mutant mice•Environmental differences drive variation in population frequencies of immune cells•Cytokine responses to microbial stimulation are affected more by genetic mutations•Multi-omic models identify responses to specific microbes driven by rewilding
The effect of genetics verses environment on immunity is incompletely understood. By releasing laboratory mice carrying IBD susceptibility genes into the outdoors, Lin et al. find that exposure to environmental microbes promotes variation in immune cell populations, whereas cytokine responses to microbial stimulation are affected more by genetic IBD susceptibility.
Free-living mammals, such as humans and wild mice, display heightened immune activation compared with artificially maintained laboratory mice. These differences are partially attributed to microbial ...exposure as laboratory mice infected with pathogens exhibit immune profiles more closely resembling that of free-living animals. Here, we examine how colonization by microorganisms within the natural environment contributes to immune system maturation by releasing inbred laboratory mice into an outdoor enclosure. In addition to enhancing differentiation of T cell populations previously associated with pathogen exposure, outdoor release increased circulating granulocytes. However, these “rewilded” mice were not infected by pathogens previously implicated in immune activation. Rather, immune system changes were associated with altered microbiota composition with notable increases in intestinal fungi. Fungi isolated from rewilded mice were sufficient in increasing circulating granulocytes. These findings establish a model to investigate how the natural environment impacts immune development and show that sustained fungal exposure impacts granulocyte numbers.
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•Controlled release of lab mice into the wild alters the state of the immune system•Rewilded mice harbor an altered microbiota including increases in intestinal fungi•Fungi from rewilded mice induce granulocyte expansion in laboratory mice
Laboratory mice are maintained in artificial conditions that potentially impact immunity. In this issue of Cell Host & Microbe, Yeung et al. (2020) demonstrate that mice released into a wild enclosure display increases in circulating granulocytes that are associated with an altered microbiota, notably expansion of fungi.
The purpose of this study was to examine the scientific evidence for a dose-response relation of physical activity with depressive and anxiety disorders.
Computer database searches of MEDLINE, ...PsychLit, and Internet and personal retrieval systems to locate population studies, randomized controlled trials (RCTs), observational studies, and consensus panel judgments were conducted.
Observational studies demonstrate that greater amounts of occupational and leisure time physical activity are generally associated with reduced symptoms of depression. Quasi-experimental studies show that light-, moderate-, and vigorous-intensity exercise can reduce symptoms of depression. However, no RCTs have varied frequency or duration of exercise and controlled for total energy expenditure in studies of depression or anxiety. Quasi-experimental and RCTs demonstrate that both resistance training and aerobic exercise can reduce symptoms of depression. Finally, the relation of exercise dose to changes in cardiorespiratory fitness is equivocal with some studies showing that fitness is associated with reduction of symptoms and others that have demonstrated reduction in symptoms without increases in fitness.
All evidence for dose-response effects of physical activity and exercise come from B and C levels of evidence. There is little evidence for dose-response effects, though this is largely because of a lack of studies rather than a lack of evidence. A dose-response relation does, however, remain plausible.
The Aerobics Center Longitudinal Study (ACLS) provides the opportunity to evaluate associations between measures of physical activity and mental health in a large and well-characterized population of ...men and women.
Participants were 5451 men and 1277 women (20-88 yr) who completed a maximal fitness treadmill test and self-report measures of habitual physical activity, depressive symptoms (Center for Epidemiological Studies Scale for Depression; CES-D) and emotional well-being (General Well-Being Schedule; GWB). To evaluate the dose-response gradient of the association, we classified the sample, separately for men and women, into three levels of relative cardiorespiratory (CR) fitness (low, moderate, high) on the maximal treadmill test, and four levels on a physical activity index of weekly walking, jogging, and running.
In both men and women, there was a significant inverse graded dose-response relationship between maximal CR fitness and the CES-D score (P < 0.0001), and a significant positive graded dose-response relationship between CR fitness and the GWB score (P < 0.0001). We also observed dose-response associations between the level of physical activity and both CES-D and GWB scores (P < 0.0001) that peaked at 11-19 miles per week.
Among men and women in the ACLS, relative increases in maximal CR fitness and habitual physical activity are cross-sectionally associated with lower depressive symptomatology and greater emotional well-being. Prospective epidemiological studies and controlled clinical trials are needed to identify the minimal and optimal levels of physical activity and CR fitness associated with various mental health benefits in different segments of the general population.
The National Institute of Mental Health convened a meeting in October 2005 to review the literature on obesity, nutrition, and physical activity among those with mental disorders. The findings of ...this meeting and subsequent update of the literature review are summarized here. Levels of obesity are higher in those with schizophrenia and depression, as is mortality from obesity-related conditions such as coronary heart disease. Medication side effects, particularly the metabolic side effects of antipsychotic medications, contribute to the high levels of obesity in those with schizophrenia, but increased obesity and visceral adiposity have been found in some but not all samples of drug-naïve patients as well. Many of the weight-management strategies used in the general population may be applicable to those with mental disorders, but little is known about the effects of these strategies on this patient population or how these strategies may need to be adapted for the unique needs of those with mental disorders. The minimal research on weight-management programs for those with mental disorders indicates that meaningful changes in dietary intake and physical activity are possible. Physical activity is an important component of any weight-management program, particularly for those with depression, for which a substantial body of research indicates both mental and physical health benefits. Obesity among those with mental disorders has not received adequate research attention, and empirically-based interventions to address the increasing prevalence of obesity and risk of cardiovascular and metabolic diseases in this population are lacking.
This study aims to determine the efficacy of exercise training for alleviating vasomotor and other menopausal symptoms.
Late perimenopausal and postmenopausal sedentary women with frequent vasomotor ...symptoms (VMS) participated in a randomized controlled trial conducted in three sites: 106 women randomized to exercise and 142 women randomized to usual activity. The exercise intervention consisted of individual facility-based aerobic exercise training three times per week for 12 weeks. VMS frequency and bother were recorded on daily diaries at baseline and on weeks 6 and 12. Intent-to-treat analyses compared between-group differences in changes in VMS frequency and bother, sleep symptoms (Insomnia Severity Index and Pittsburgh Sleep Quality Index), and mood (Patient Health Questionnaire-8 and Generalized Anxiety Disorder-7 questionnaire).
At the end of week 12, changes in VMS frequency in the exercise group (mean change, -2.4 VMS/d; 95% CI, -3.0 to -1.7) and VMS bother (mean change on a four-point scale, -0.5; 95% CI, -0.6 to -0.4) were not significantly different from those in the control group (-2.6 VMS/d; 95% CI, -3.2 to -2.0; P = 0.43; -0.5 points; 95% CI, -0.6 to -0.4; P = 0.75). The exercise group reported greater improvement in insomnia symptoms (P = 0.03), subjective sleep quality (P = 0.01), and depressive symptoms (P = 0.04), but differences were small and not statistically significant when P values were adjusted for multiple comparisons. Results were similar when considering treatment-adherent women only.
These findings provide strong evidence that 12 weeks of moderate-intensity aerobic exercise do not alleviate VMS but may result in small improvements in sleep quality, insomnia, and depression in midlife sedentary women.
Most patients with major depressive disorder (MDD) require second-step treatments to achieve remission. The Treatment with Exercise Augmentation for Depression (TREAD) study was designed to test the ...efficacy of aerobic exercise as an augmentation treatment for MDD patients who had not remitted with antidepressant treatment.
Eligible participants in this randomized controlled trial were sedentary individuals (men and women aged 18-70 years) diagnosed with DSM-IV nonpsychotic MDD who had not remitted with selective serotonin reuptake inhibitor (SSRI) treatment. Participants were recruited through physician referrals and advertisements. A total of 126 participants were randomized to augmentation treatment with either 16 kcal per kg per week (KKW) or 4 KKW of exercise expenditure for 12 weeks while SSRI treatment was held constant. Supervised sessions were conducted at The Cooper Institute, Dallas, Texas, with additional home-based sessions as needed to fulfill the weekly exercise prescription. The primary outcome was remission (as determined by a score ≤ 12 on the Inventory of Depressive Symptomatology, Clinician-Rated). The study took place between August 2003 and August 2007.
There were significant improvements over time for both groups combined (F₁,₁₂₁ = 39.9, P < .0001), without differential group effect (group effect: F₁,₁₃₄ = 3.2, P = .07; group-by-time effect: F₁,₁₁₉ = 3.8, P = .06). Adjusted remission rates at week 12 were 28.3% versus 15.5% for the 16-KKW and 4-KKW groups, respectively, leading to a number needed to treat (NNT) of 7.8 for 16 KKW versus 4 KKW. Men, regardless of family history of mental illness, and women without a family history of mental illness had higher remission rates by week 12 with higher-dose (women, 39.0%; men, 85.4%) than with lower-dose exercise (women, 5.6%; men, 0.1%) (women: t₉₅ = 2.1, P = .04; men: t₈₈ = 5.4, P < .0001) (NNT: women, 3.0; men, 1.2).
There was a trend for higher remission rates in the higher-dose exercise group (P < .06), with a clinically meaningful NNT of 7.8 in favor of the high exercise dose. Significant differences between groups were found when the moderating effects of gender and family history of mental illness were taken into account and suggest that higher-dose exercise may be better for all men and for women without a family history of mental illness.
clinicaltrials.gov Identifier: NCT00076258.
The stratosphere can have a significant impact on winter surface weather on subseasonal to seasonal (S2S) timescales. This study evaluates the ability of current operational S2S prediction systems to ...capture two important links between the stratosphere and troposphere: (1) changes in probabilistic prediction skill in the extratropical stratosphere by precursors in the tropics and the extratropical troposphere and (2) changes in surface predictability in the extratropics after stratospheric weak and strong vortex events. Probabilistic skill exists for stratospheric events when including extratropical tropospheric precursors over the North Pacific and Eurasia, though only a limited set of models captures the Eurasian precursors. Tropical teleconnections such as the Madden‐Julian Oscillation, the Quasi‐Biennial Oscillation, and El Niño–Southern Oscillation increase the probabilistic skill of the polar vortex strength, though these are only captured by a limited set of models. At the surface, predictability is increased over the United States, Russia, and the Middle East for weak vortex events, but not for Europe, and the change in predictability is smaller for strong vortex events for all prediction systems. Prediction systems with poorly resolved stratospheric processes represent this skill to a lesser degree. Altogether, the analyses indicate that correctly simulating stratospheric variability and stratosphere‐troposphere dynamical coupling are critical elements for skillful S2S wintertime predictions.
Key Points
Tropospheric precursors of SSW events are better represented for the North Pacific than for Eurasia
Teleconnections from the tropics add probabilistic skill but are only represented by a few models
Weak and strong vortex events in the NH stratosphere can contribute to surface skill 3–4 weeks later
This study, conducted between 1998 and 2001 and analyzed in 2002 and 2003, was designed to test (1) whether exercise is an efficacious treatment for mild to moderate major depressive disorder (MDD), ...and (2) the dose-response relation of exercise and reduction in depressive symptoms.
The study was a randomized 2x2 factorial design, plus placebo control.
All exercise was performed in a supervised laboratory setting with adults (n =80) aged 20 to 45 years diagnosed with mild to moderate MDD.
Participants were randomized to one of four aerobic exercise treatment groups that varied total energy expenditure (7.0 kcal/kg/week or 17.5 kcal/kg/week) and frequency (3 days/week or 5 days/week) or to exercise placebo control (3 days/week flexibility exercise). The 17.5-kcal/kg/week dose is consistent with public health recommendations for physical activity and was termed "public health dose" (PHD). The 7.0-kcal/kg/week dose was termed "low dose" (LD).
The primary outcome was the score on the 17-item Hamilton Rating Scale for Depression (HRSD(17)).
The main effect of energy expenditure in reducing HRSD(17) scores at 12 weeks was significant. Adjusted mean HRSD(17) scores at 12 weeks were reduced 47% from baseline for PHD, compared with 30% for LD and 29% for control. There was no main effect of exercise frequency at 12 weeks.
Aerobic exercise at a dose consistent with public health recommendations is an effective treatment for MDD of mild to moderate severity. A lower dose is comparable to placebo effect.
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