Gymnastik- och idrottshögskolan, GIH

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. 

Mental disorders pose a significant global health challenge. To effectively address this challenge, mental health promotion must be included in various sectors, including workplaces. Various strategies for promoting mental health in the workplace have been suggested, including interventions aimed at improving movement behavior, i.e., sitting less and moving more. Physical activity (PA) and sedentary behavior (SED) are established determinants of mental health. However, there are aspects of the relationship between movement behavior and mental health that are not well understood, for example, the combined effects of all movement behaviors occurring throughout the daily 24-hour cycle, i.e., time in bed, SED, light-intensity physical activity, and moderate to vigorous physical activity (MVPA), on mental health. In addition, only a few well-designed workplace interventions for improving movement and mental health outcomes have been tested. Office workers often spend extensive amounts of time being sedentary and might particularly benefit from such interventions. The aims of this thesis were (1) to investigate cross-sectional associations between 24-hour movement behavior and mental health among office workers and (2) to evaluate the efficacy, acceptability, feasibility, and fidelity of two cluster randomized controlled trial (RCT) interventions for improving movement behavior and mental health using quantitative and qualitative methods.

In Paper I, we investigated cross-sectional associations between 24-hour movement behavior and mental health outcomes (symptoms of depression and anxiety, burnout, mental wellbeing, and stress) among office workers (N=345-370). Movement behavior was measured using accelerometers and sleep diaries. Mental health outcomes were assessed using validated questionnaires. Only the proportion of time spent in MVPA, relative to all other behaviors, was positively associated with mental wellbeing. 

Papers II-IV were based on a three-armed cluster RCT among office workers (N=263). During the 6-month intervention period, the iSED intervention group focused on reducing SED, and the iPA intervention group focused on increasing MVPA compared to a wait-list control group. The multi-level interventions were designed based on ecological models of health behavior, addressing the individual office workers as well as their physical, social, and organizational work environment. Paper II investigated intervention effects on accelerometer-measured 24-hour movement behavior and cardiorespiratory fitness. We considered overall 24-hour movement behavior and movement behavior during work versus non-work time. No intervention effects were found. Paper III was based on a qualitative study that was embedded in the RCT. It investigated the acceptability, feasibility, and fidelity of intervention components that addressed the individual, environmental and organizational level. Interviews and focus group discussions were performed with 38 key stakeholders after the 6-month intervention period. The study included office workers who received the interventions, health coaches who delivered counseling sessions, team leaders who were responsible for implementing group activities, and human resource and higher management staff who provided support at the organizational level. In general, the interventions were well appreciated, and components seemed to work as intended when delivered as intended. Many office workers experienced improvements in movement behavior and wellbeing and ascribed those to the interventions. Acceptability, feasibility, and fidelity of individual-level components were high but reduced for components depending on team leaders, mainly due to challenges associated with recruiting managers as team leaders and forming teams. Manager and team support were considered crucial for promoting more PA and less SED, yet many participants reported a lack of such support. Thus, identified challenges with these components might have reduced overall intervention efficacy. Paper IV investigated intervention effects on mental health outcomes (symptoms of depression or anxiety, mental wellbeing, and stress). In addition, we explored whether changes in mean PA intensity mediated or moderated intervention effects. The interventions improved mental wellbeing for the combined intervention groups and the iSED group but not for the iPA group compared to the control group. The interventions improved mean PA intensity, but mean PA intensity did not mediate intervention effects on any outcome. Mean PA intensity moderated intervention effects on mental wellbeing. Participants who reduced mean PA intensity reduced mental wellbeing compared to participants who did not change mean PA intensity. This highlights the importance of maintaining high levels of PA for mental wellbeing.

This thesis contributes to existing knowledge by applying a rigorous investigation of cross-sectional associations between 24-h movement behavior and mental health among office workers and by conducting a comprehensive analysis of intervention effects. It offers valuable insights and considerations that may inform occupational health practitioners, employers, policy makers, and researchers and may contribute to developing future effective interventions.