title: Association between physical activity and serum C-peptide levels among the elderly.
abstract: OBJECTIVE
  Serum C-peptide is an active peptide that has important physiological functions and characteristics in the elderly. The present study aimed to investigate the association between physical activity and serum C-peptide level independent of insulin level among the elderly.
  
  
  METHODS
  The study included 1700 elderly participants aged ≥ 65 years. Stratified analysis of covariance was used to compare serum C-peptide levels in participants with different physical activity levels. Two separate multiple linear regression models were created to estimate the association between physical activity and serum C-peptide level.
  
  
  RESULTS
  The results of analysis of covariance stratified by sex, body mass index and serum insulin level showed that those who engaged in vigorous physical activity had lower serum C-peptide levels than those who engaged in light or no physical activity. Separate multiple linear regression analysis showed that in those with low serum C-peptide levels (≤ 0.621 nmol/L), physical activity was significantly positively associated with the serum C-peptide level. In contrast, physical activity was negatively associated with the serum C-peptide level among those with serum C-peptide level >0.621 nmol/L.
  
  
  CONCLUSIONS
  The serum C-peptide level showed a significant two-way association with physical activity. The present findings suggest that physical activity modification is important for improving serum C-peptide levels among the elderly.
authors.affiliation: Department of Social Medicine, School of Public Health, Zhejiang University, Hangzhou, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Lu
authors.initials: L
authors.lastname: Meng
authors.forename: QianQian
authors.initials: Q
authors.lastname: Miao
authors.forename: Yasuto
authors.initials: Y
authors.lastname: Sato
mesh_terms: D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009749:Nutrition Surveys; D057185:Sedentary Behavior; D012737:Sex Factors; D014481:United States / Q000453:epidemiology
chemical_list: D002096:C-Peptide; D007328:Insulin
keywords: C-peptide; elderly; insulin; physical activity; public health