Krueger, B.* ; Stutz, B.* ; Jankovic, N.* ; Alexy, U.* ; Kilanowski, A. ; Libuda, L.* ; Buyken, A.E.*
     
    
        
The association of chronotype and social jet lag with body composition in German students: The role of physical activity behaviour and the impact of the pandemic lockdown.
    
    
        
    
    
        
        PLoS ONE 18:e0279620 (2023)
    
    
    
      
      
	
	    Young adults with a later chronotype are vulnerable for a discrepancy in sleep rhythm between work- and free days, called social jet lag (SJL). This study analysed (i) chronotype/SJL association with visceral fat/skeletal muscle mass, (ii) the attribution to physical activity behaviour, and (iii) chronotype-specific changes in physical activity behaviour in young adults during the Covid-19 pandemic lockdown. Chronotype and SJL were derived from the Munich-Chrono-Type-Questionnaire in 320 German students (age 18-25 years) from September 2019 to January 2020, 156 of these participated in an online follow-up survey in June 2020. Body composition was assessed by bioimpedance analysis at baseline. Multivariable linear regression analyses were used to relate chronotype/SJL to body composition; the contribution of self-reported physical activity was tested by mediation analysis. At baseline, a later chronotype and a larger SJL were associated with a higher visceral fat mass (P<0.05), this relation was notably mediated by the attention to physical activity (P<0.05). Chronotype (P = 0.02) but not SJL (P = 0.87) was inversely associated with skeletal muscle mass. During the pandemic lockdown, chronotype hardly changed, but SJL was reduced. Timing and physical activity behaviour remained in most participants and changes were unrelated to chronotype (all P>0.07). A later chronotype/higher SJL may increase the risk of a higher visceral fat mass even in this relatively healthy sample, which may be partly due to their physical activity behaviour. Despite a reduction in SJL during the pandemic lockdown, later chronotypes did not change their physical activity behaviour more than earlier chronotypes.
	
	
	    
	
       
      
	
	    
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        Publication type
        Article: Journal article
    
 
    
        Document type
        Scientific Article
    
 
    
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        Keywords
        Food-intake; Typology; Season; Sleep; Time
    
 
    
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        Language
        english
    
 
    
        Publication Year
        2023
    
 
    
        Prepublished in Year
        0
    
 
    
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        2023
    
 
    
    
        ISSN (print) / ISBN
        1932-6203
    
 
    
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	    Volume: 18,  
	    Issue: 1,  
	    Pages: ,  
	    Article Number: e0279620 
	    Supplement: ,  
	
    
 
    
        
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            Public Library of Science (PLoS)
        
 
        
            Publishing Place
            Lawrence, Kan.
        
 
	
        
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        Reviewing status
        Peer reviewed
    
 
    
        Institute(s)
        Institute of Epidemiology (EPI)
    
 
    
        POF-Topic(s)
        30202 - Environmental Health
    
 
    
        Research field(s)
        Genetics and Epidemiology
    
 
    
        PSP Element(s)
        G-504000-008
    
 
    
        Grants
        German Research Foundation (DFG)
    
 
    
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        Erfassungsdatum
        2023-01-17