Gymnastik- och idrottshögskolan, GIH

OBJECTIVES: To examine the associations between changes in cardiorespiratory fitness (CRF) in adulthood and prostate cancer incidence and mortality.

METHODS: In this prospective study, men who completed an occupational health profile assessment including at least two valid submaximal CRF tests, performed on a cycle ergometer, were included in the study. Data on prostate cancer incidence and mortality were derived from national registers. HRs and CIs were calculated using Cox proportional hazard regression with inverse probability treatment weights of time-varying covariates.

RESULTS: During a mean follow-up time of 6.7 years (SD 4.9), 592 (1%) of the 57 652 men were diagnosed with prostate cancer, and 46 (0.08%) died with prostate cancer as the primary cause of death. An increase in absolute CRF (as % of L/min) was associated with a reduced risk of prostate cancer incidence (HR 0.98, 95% CI 0.96 to 0.99) but not mortality, in the fully adjusted model. When participants were grouped as having increased (+3%), stable (±3%) or decreased (-3%) CRF, those with increased fitness also had a reduced risk of prostate cancer incidence compared with those with decreased fitness (HR 0.65, 95% CI 0.49 to 0.86), in the fully adjusted model.

CONCLUSION: In this study of employed Swedish men, change in CRF was inversely associated with risk of prostate cancer incidence, but not mortality. Change in CRF appears to be important for reducing the risk of prostate cancer.

BACKGROUND: Physical activity (PA) is increasingly used as an adjunct treatment for alcohol use disorder (AUD). Previous studies have relied on self-report measures of PA, which are prone to measurement error. In the context of a randomized controlled trial of PA for AUD, we examined: (1) associations between device-measured and self-reported PA, (2) associations between PA measurements and alcohol use, and (3) the feasibility of obtaining device-measured PA data in this population.

METHOD: One-hundred and forty individuals with clinician-diagnosed AUD participated in a 12-week intervention comparing usual care (phone counselling) to yoga-based exercise and aerobic exercise. Device-measured PA (Actigraph GT3x), self-reported PA (International Physical Activity Questionnaire) and alcohol consumption (Timeline Follow Back Method) were assessed before and after the trial. Effects of the interventions on PA levels were assessed using linear mixed models.

RESULTS: In total, 42% (n=59) of participants returned usable device-measured PA data (mean age= 56±10 years, 73% male). Device-measured and self-reported vigorous-intensity PA were correlated (β= -0.02, 95%CI= -0.03, -0.00). No associations were found for moderate-intensity PA. Compared to usual care, time spent in device-measured light-intensity PA increased in the aerobic exercise group (∆= 357, 95%CI= 709, 5.24). Increases in device-measured light-intensity PA were associated with fewer standard drinks (∆= -0.24, 95%CI= -0.03, -0.44), and fewer heavy drinking days (∆= -0.06, 95%CI=-0.01, -0.10).

CONCLUSION: Increases in light-intensity/habitual PA were associated with less alcohol consumption in adults with AUD. Self-reported PA data should be interpreted with caution. Incentives are needed to obtain device-measured PA data in AUD populations.

INTRODUCTION: The aim of this prospective cohort study was to investigate the associations between changes in cardiorespiratory fitness (CRF) and the risk of colorectal and prostate cancer in men.

METHODS: Data from men who completed a health assessment both in military conscription in youth and an occupational health profile assessment (HPA) later in life were used. CRF was assessed as estimated V̇O_2max, using a cycle ergometer fitness test at both time points. We linked the assessment data to national register data on colorectal and prostate cancer incidence, and hazard ratios and confidence intervals were estimated using Cox proportional hazard regression.

RESULTS: 139,764 men with a mean age of 18 (SD 0.6) at conscription and 43 (SD 8.9) at HPA were included. The average time between the two assessments was 25.9 (SD 9.0) years and mean follow-up time following HPA test was 10.0 (SD 5.6) years for prostate and colorectal cancer. Annual percentage change in relative and absolute V̇O_2max from conscription to HPA was inversely associated with the risk of colorectal cancer incidence, hazard ratio of 0.83 (95% CI [0.72-0.94]) and 0.88 (95% CI [0.79-0.99]), respectively. These associations were driven by data from individuals in the lowest and moderate level fitness tertials at conscription. Change in CRF was not associated with prostate cancer incidence risk.

CONCLUSIONS: Changes in, not only level of, CRF from youth to adulthood are related to colorectal cancer incidence risk and therefore, improving CRF should be considered as an important colorectal cancer risk reduction strategy.

IMPORTANCE: Cardiorespiratory fitness (CRF) levels appear to be an important risk factor for cancer incidence and death.

OBJECTIVES: To examine CRF and prostate, colon, and lung cancer incidence and mortality in Swedish men, and to assess whether age moderated any associations between CRF and cancer.

DESIGN, SETTING, AND PARTICIPANTS: A prospective cohort study was conducted in a population of men who completed an occupational health profile assessment between October 1982 and December 2019 in Sweden. Data analysis was performed from June 22, 2022, to May 11, 2023.

EXPOSURE: Cardiorespiratory fitness was assessed as maximal oxygen consumption, estimated using a submaximal cycle ergometer test.

MAIN OUTCOMES AND MEASURES: Data on prostate, colon, and lung cancer incidence and mortality were derived from national registers. Hazard ratios (HRs) and 95% CIs were calculated using Cox proportional hazards regression.

RESULTS: Data on 177 709 men (age range, 18-75 years; mean [SD] age, 42 [11] years; mean [SD] body mass index, 26 [3.8]) were analyzed. During a mean (SD) follow-up time of 9.6 (5.5) years, a total of 499 incident cases of colon, 283 of lung, and 1918 of prostate cancer occurred, as well as 152 deaths due to colon cancer, 207 due to lung cancer, and 141 deaths due to prostate cancer. Higher levels of CRF (maximal oxygen consumption as milliliters per minute per kilogram) were associated with a significantly lower risk of colon (HR, 0.98, 95% CI, 0.96-0.98) and lung cancer (HR, 0.98; 95% CI, 0.96-0.99) incidence, and a higher risk of prostate cancer incidence (HR, 1.01; 95% CI, 1.00-1.01). Higher CRF was associated with a lower risk of death due to colon (HR, 0.98; 95% CI, 0.96-1.00), lung (HR, 0.97; 95% CI, 0.95-0.99), and prostate (HR, 0.95; 95% CI, 0.93-0.97) cancer. After stratification into 4 groups and in fully adjusted models, the associations remained for moderate (>35-45 mL/min/kg), 0.72 (0.53-0.96) and high (>45 mL/min/kg), 0.63 (0.41-0.98) levels of CRF, compared with very low (<25 mL/min/kg) CRF for colon cancer incidence. For prostate cancer mortality, associations remained for low (HR, 0.67; 95% CI, 0.45-1.00), moderate (HR, 0.57; 95% CI, 0.34-0.97), and high (HR, 0.29; 95% CI, 0.10-0.86) CRF. For lung cancer mortality, only high CRF (HR, 0.41; 95% CI, 0.17-0.99) was significant. Age modified the associations for lung (HR, 0.99; 95% CI, 0.99-0.99) and prostate (HR, 1.00; 95% CI, 1.00-1.00; P < .001) cancer incidence, and for death due to lung cancer (HR, 0.99; 95% CI, 0.99-0.99; P = .04).

CONCLUSIONS AND RELEVANCE: In this cohort of Swedish men, moderate and high CRF were associated with a lower risk of colon cancer. Low, moderate, and high CRF were associated with lower risk of death due to prostate cancer, while only high CRF was associated with lower risk of death due to lung cancer. If evidence for causality is established, interventions to improve CRF in individuals with low CRF should be prioritized.

Brain-derived neurotrophic factor (BDNF) and cortisol are both capable of modulating synaptic plasticity, but it is unknown how physical activity-induced changes in their plasma levels relate to corticospinal plasticity in humans. Sixteen inactive middle-aged men and women participated in three separate interventions consisting of 3hours prolonged sitting (SIT); 3hours sitting interrupted every 30minutes with frequent short physical activity breaks (FPA); and 2.5hours prolonged sitting followed by 25minutes of moderate intensity exercise (EXE). These 3hour sessions were each followed by a 30min period of paired associative stimulation over the primary motor cortex (PAS). Blood samples were taken and corticospinal excitability measured at baseline, pre PAS, 5min and 30min post PAS. Here we report levels of plasma BDNF and cortisol over three activity conditions and relate these levels to previously published changes in corticospinal excitability of a non-activated thumb muscle. There was no interaction between time and condition in BDNF, but cortisol levels were significantly higher after EXE compared to after SIT and FPA. Higher cortisol levels at pre PAS predicted larger increases in corticospinal excitability from baseline to all subsequent time points in the FPA condition only, while levels of BDNF at pre PAS did not predict such changes in any of the conditions. Neither BDNF nor cortisol modified changes from pre PAS to the subsequent time points, suggesting that the increased corticospinal excitability was not mediated though an augmented effect of the PAS protocol. The relationship between cortisol and plasticity has been suggested to be U-shaped. This is possibly why the moderately high levels of cortisol seen in the FPA condition were positively associated with changes AURC, while the higher cortisol levels seen after EXE were not. A better understanding of the mechanisms for how feasible physical activity breaks affect neuroplasticity can inform the theoretical framework for how work environments and schedules should be designed. DATA AVAILABILITY: Data are available from the corresponding author upon reasonable request.

The lifetime trajectories of movement behavior and cognitive functioning depend on complex interactions between genetic and environmental factors. There is substantial evidence suggesting that physical activity benefits cognitive functions. However, how sedentary behavior and the composition of movement behaviors (i.e., sleep, physical activity, and sedentary behavior) influences cognitive functions remains to be elucidated. 

Observational studies suggest that sedentary time is unfavorably related to cognitive functions in older adults, but the majority of evidence comes from self-reported estimates of movement behavior, which are rather weakly related to device-based measures. Furthermore, while evidence suggests that structured exercise can have protective effects on cognition in inactive older adults, much less is known about how midlife movement behavior is related to cognitive functions. Thus, knowledge of how midlife movement behavior relates to and possibly affects cognitive functions and its underlying mechanisms is much needed. 

This thesis is part of a larger research project investigating how movement behaviors relate to and influence cognitive function, mental health, and neurophysiological mechanisms underpinning these. The project specifically targets healthy office workers and is co-produced with employers of office workers and health-promoting companies. This thesis aimed to investigate how movement behaviors relate to and influence cognitive functions and neuroplasticity among office workers.

The first study investigated cross-sectional relationships between device-measured movement behavior and cognitive functions among 334 office workers. The results revealed no association between total time spent in moderate to vigorous physical activity or sedentary behavior and cognitive functions, suggesting that this association may not be as robust as previously suggested in older populations or as inferred from self-report. 

The second study investigated the extent to which corticospinal excitability is influenced by different movement behaviors. Sixteen sedentary office workers participated in a cross-over randomized controlled trial. We contrasted 3 hours of prolonged sitting with 3 hours of interrupted sitting and 2.5 hours sitting followed by a 25-minute bout of exercise. Acute changes in corticospinal excitability and long-term potentiation-like neuroplasticity were investigated using transcranial magnetic stimulation and paired associative stimulation. Changes in corticospinal excitability over time did not differ between conditions, suggesting that in inactive middle-aged office workers, a physical activity bout or frequently breaking up prolonged sitting does not induce immediate changes in corticospinal excitability or long-term potentiation-like neuroplasticity. 

The third and fourth studies are based on a 6-month cluster-randomized intervention conducted in 263 healthy office workers. An ecological model for behavior change was used to design two interventions aiming at reducing sedentary behavior or increasing physical activity relative to a passive control group, with the ultimate aim of improving cognitive functions and mental health. The third study investigated how effective each intervention was at changing the 24-hour movement behavior, and the fourth study examined intervention effects on cognitive functions. The results showed that the interventions were ineffective in reducing sedentary behavior and increasing physical activity, respectively, with no detected beneficial effects on cardiorespiratory fitness or cognitive functions relative to the control group. Changes in cognition from baseline to follow-up were not associated with changes in the composition of movement behaviors or cardiorespiratory fitness, but some associations between changes in movement behaviors and cognition were moderated by sex, age, and cardiorespiratory fitness. Thus, the third and fourth studies of the thesis have highlighted the challenges involved in successfully achieving movement behavior change to address the possible effects on cognitive improvements in an ecological setting.

In summary, the results presented in this thesis did not provide support for an association between movement behaviors and cognitive functions in healthy physically active office workers, demonstrated no acute effect of a single session of physical activity or breaking up prolonged sitting on corticospinal excitability in sedentary office workers, and revealed no evidence for successful movement behavior change or benefits for cognition in an ecological cluster-randomized intervention in healthy physically active office workers. The findings suggest that among physically active office workers, sedentary behavior may not be as detrimental for cognition and neuroplasticity as previously suggested and shows that changing movement behavior in office workers at the workplace represents a challenging endeavor. Still, these findings do not exclude the possibility that changes in movement behaviors might benefit cognitive functions in physically inactive office workers at higher cardiovascular risk, with lower cardiorespiratory fitness and/or lower daily cognitive stimulation. 

Utvecklingen genom livet av såväl kognitiv förmåga som fysiskt aktivitetsmönster beror på en komplex interaktion mellan arv och miljö. Det finns stark evidens för att fysisk aktivitet kan förbättra kognitiv förmåga, men vi saknar kunskap om hur stillasittande och det sammansatta fysiska aktivitetsmönstret (omfattande sömn, fysiskt aktivitet och stillasittande) påverkar kognition.

Observationsstudier på äldre har visat att mer stillasittande tid är relaterat till sämre kognitiv prestation, men de flesta av dessa studier har utgått från självskattat stillasittande. Självskattningar av fysisk aktivitet och stillasittande är ofta ganska svagt associerade till uppmätt fysiskt aktivitetsmönstret. Emedan träning har visat sig ha en skyddande effekt på äldres kognition, så vet man fortfarande väldigt lite om hur det fysiska aktivitetsmönstret i den arbetsföra befolkningen relaterar till och påverkar kognition. Därför behövs det kunskap om hur fysiskt aktivitetsmönster i medelåldern påverkar kognition och vilka mekanismer som ligger till grund för denna effekt.       

Avhandlingen är en del av ett större forskningsprojekt som syftar till att undersöka hur kontorsarbetares fysiska aktivitetsmönster relaterar till och påverkar kognition, psykisk hälsa och neurofysiologiska mekanismer för dessa. Kunskapen samproduceras med arbetsgivare och friskvårdsföretag.

Syftet med denna avhandling var att belysa hur kontorsarbetares fysiska aktivitetsmönster relaterar till och påverkar kognition och neuroplasticitet.

Avhandlingens första studie undersökte sambandet mellan fysiska aktivitetsmönster och kognitiva förmågor bland 334 kontorsarbetare. Studien visade inga samband mellan total tid i medel-till-högintensiv fysisk aktivitet eller stillasittande och prestationen på kognitiva tester. Detta tyder på att sambandet som tidigare påvisats i äldre mellan fysiskt aktivitetsmönster och kognitiva funktioner inte går att generalisera till medelåldern.    

Den andra studien undersökte omedelbara effekter av tre timmars stillasittande uppbrutet av tre olika rörelseinterventioner på kortikospinal neuroplasticitet. Sexton inaktiva kontorsarbetare i medelåldern deltog i tre separata interventioner, genomförda i randomiserad ordning, separerade av minst 7 dagar. Effekter av tre timmars stillasittande jämfördes med tre timmars stillasittande uppbrutet med korta rörelsepauser eller 2,5 timmars stillasittande följt av 25 minuters medelintensiv träning. Transkraniell magnetstimulation användes för att utvärdera kortikospinal retbarhet och svaret på ett neuroplasticitetsinducerande protokoll. Studien fann inga statistiskt säkerställda skillnader mellan de tre experimentella interventionerna. Detta tyder på att ett enskilt träningspass eller uppbrutet stillasittande inte är mer fördelaktigt än långvarigt stillasittande för kortikospinal neuroplasticitet eller retbarhet bland inaktiva kontorsarbetare.     

Vi genomförde sedan en sex månaders ekologisk klusterrandomiserad multikomponent intervention med stöd till mer fysisk aktivitet eller minskat stillasittande bland 263 friska kontorsarbetare i syfte att främja hälsosamma hjärnfunktioner. Stödet gavs på individ, miljö och organisationsnivå. Den tredje studien undersökte hur effektiva interventionerna var på att ändra sammansättningen av det fysiska aktivitetsmönstret från studiens start till sex-månaders-uppföljningen. Den fjärde studien undersökte hur interventionerna påverkade kognition. Varken fysiska aktivitetsmönster, kondition eller kognitiva funktioner påverkades av interventionerna. Ändringar i fysiska aktivitetsmönster och kondition var inte relaterade till ändringar i kognition. Relationen mellan förändringar i sammansättningen av fysiskt aktivitetsmönster och kognition modererades till viss del av kön, ålder och kondition.

Denna avhandling fann sammanfattningsvis inga stöd för samband mellan fysiskt aktivitetsmönster och kognition bland friska kontorsarbetare, inga omedelbara effekt av ett träningspass eller uppbrutet stillasittande på kortikospinal neuroplasticitet bland inaktiva kontorsarbetare och inget stöd för att de utvärderade ekologiska klusterrandomiserade interventionerna med stöd på individ, miljö och organisationsnivå hade effekter på fysiskt aktivitetsmönster eller kognition bland friska kontorsarbetare. Sammantaget tyder fynden på att stillasittande nog inte är så negativt för kognitionen och neuroplasticiteten bland friska, fysiskt aktiva kontorsabetare som tidigare föreslagits. Dessutom belyser resultaten svårigheten med att stödja hållbara förändringar i fysiskt aktivitetsmönster via arbetsplatsen.

Vi kan inte utesluta möjligheten att ändringar i fysiskt aktivitetsmönster kan leda till förbättringar i kognition för fysiskt inaktiva kontorsarbetare med risk för kardiovaskulär sjukdom, lägre kondition och/eller lägre daglig kognitiv stimulation. Framtida interventioner skulle kunna utformas med en mer avgränsad målgrupp i fokus. 

BACKGROUND: We previously reported the effects of two cluster-randomized 6-month multi-component workplace interventions, targeting reducing sedentary behavior or increasing physical activity among office workers, on movement behaviors and cardiorespiratory fitness. The primary aim of this study was to investigate the effects of these interventions on cognitive functions compared to a wait-list control group. The secondary aims were to examine if changes in cognition were related to change in cardiorespiratory fitness or movement behaviors and if age, sex, or cardiorespiratory fitness moderated these associations.

METHODS: Both interventions encompassed multi-components acting on the individual, environmental, and organizational levels and aimed to change physical activity patterns to improve mental health and cognitive function. Out of 263 included participants, 139 (mean age 43 years, 76% females) completed a neuropsychological test battery and wore accelerometers at baseline and 6-month follow-up. The intervention effect (aim 1) on cognitive composite scores (i.e., Executive Functions, Episodic Memory, Processing Speed, and Global Cognition) was investigated. Additionally, associations between changes in movement behaviors and cardiorespiratory fitness, and changes in cognition were examined (aim 2). Moreover, age, sex, and cardiorespiratory fitness level were investigated as possible moderators of change associations (aim 3).

RESULTS: Overall, cognitive performance improved from baseline to follow-up, but the change did not differ between the intervention groups and the control group. Changes in cardiorespiratory fitness or any movement behavior category did not predict changes in cognitive functions. The association between changes in time in bed and changes in both Executive Function and Global Cognition were moderated by age, such that a more positive relation was seen with increasing age. A less positive association was seen between changes in sedentary behavior and Processing Speed for men vs. women, whereas higher cardiorespiratory fitness was related to a more positive association between changes in moderate-intensity physical activity and Global Cognition.

CONCLUSION: The lack of an intervention effect on cognitive functions was expected since the intervention did not change movement behavior or fitness. Age, sex, and cardiorespiratory fitness level might moderate the relationships between movement behaviors and cognitive functions changes.

TRIAL REGISTRATION: ISRCTN92968402 . Registered 09/04/2018.

The bi-directional, day-to-day associations between daytime physical activity and sedentary behavior, and nocturnal sleep, in office workers are unknown. This study investigated these associations and whether they varied by weekday or weekend day. Among 324 Swedish office workers (mean age 42.4 years; 33.3% men), moderate-to-vigorous physical activity (MVPA), and sedentary behaviors and sleep (total sleep time (TST) and sleep efficiency (SE)) were ascertained by using accelerometers (Actigraph GT3X) over 8 days. Multilevel linear mixed models were used to assess the bi-directional, day-to-day, within-person associations. Additional analyses stratified by weekend/weekday were performed. On average, participants spent 6% (57 min) of their day in MVPA and 59% (9.5 h) sedentary, and during the night, TST was 7 h, and SE was 91%. More daytime sedentary behavior was associated with less TST that night, and reciprocally, more TST at night was associated with less sedentary behavior on the following weekday. Greater TST during the night was also associated with less MVPA the next day, only on weekdays. However, daytime MVPA was not associated with TST that night. Higher nighttime SE was associated with greater time spent sedentary and in MVPA on the following day, regardless if weekday or weekend day. Sleep may be more crucial for being physically active the following day than vice versa, especially on weekdays. Nevertheless, sedentary behavior's relation with sleep time may be bi-directional. Office workers may struggle with balancing sleep and physical activity time.

Intervention studies aiming at changing movement behavior have usually not accounted for the compositional nature of time-use data. Compositional data analysis (CoDA) has been suggested as a useful strategy for analyzing such data. The aim of this study was to examine the effects of two multi-component interventions on 24-h movement behavior (using CoDA) and on cardiorespiratory fitness among office workers; one focusing on reducing sedentariness and the other on increasing physical activity. Office workers (n = 263) were cluster randomized into one of two 6-month intervention groups, or a control group. Time spent in sedentary behavior, light-intensity, moderate and vigorous physical activity, and time in bed were assessed using accelerometers and diaries, both for 24 h in total, and for work and leisure time separately. Cardiorespiratory fitness was estimated using a sub-maximal cycle ergometer test. Intervention effects were analyzed using linear mixed models. No intervention effects were found, either for 24-h behaviors in total, or for work and leisure time behaviors separately. Cardiorespiratory fitness did not change significantly. Despite a thorough analysis of 24-h behaviors using CoDA, no intervention effects were found, neither for behaviors in total, nor for work and leisure time behaviors separately. Cardiorespiratory fitness did not change significantly. Although the design of the multi-component interventions was based on theoretical frameworks, and included cognitive behavioral therapy counselling, which has been proven effective in other populations, issues related to implementation of and compliance with some intervention components may have led to the observed lack of intervention effect.

Paired associative stimulation (PAS) can induce plasticity in the motor cortex, as measured by changes in corticospinal excitability (CSE). This effect is attenuated in older and less active individuals. Although a single bout of exercise enhances PAS-induced plasticity in young, physically inactive adults, it is not yet known if physical activity interventions affect PAS-induced neuroplasticity in middle-aged inactive individuals. Sixteen inactive middle-aged office workers participated in a randomized cross-over design investigating how CSE and short-interval intracortical inhibition (SICI) were affected by PAS preceded by 3 h of sitting (SIT), 3 h of sitting interrupted every 30 min by 3 min of frequent short bouts of physical activity (FPA) and 2.5 h of sitting followed by 25 min of moderate-intensity exercise (EXE). Transcranial magnetic stimulation was applied over the primary motor cortex (M1) of the dominant abductor pollicis brevis to induce recruitment curves before and 5 min and 30 min post-PAS. Linear mixed models were used to compare changes in CSE using time and condition as fixed effects and subjects as random effects. There was a main effect of time on CSE and planned within-condition comparisons showed that CSE was significantly increased from baseline to 5 min and 30 min post-PAS, in the FPA condition, with no significant changes in the SIT or EXE conditions. SICI decreased from baseline to 5 min post-PAS, but this was not related to changes in CSE. Our findings suggest that in middle-aged inactive adults, FPAs may promote corticospinal neuroplasticity. Possible mechanisms are discussed.