title: Influences of sex and age on biological rhythms of serum lipids and lipoproteins.
abstract: BACKGROUND
  Few studies have evaluated seasonal variations of biochemical parameters routinely analyzed in clinical laboratories. Rhythmic patterns for lipids and lipoproteins have been demonstrated and have been the object of research, mainly because of their demonstrated association with coronary artery disease. This study evaluated the occurrence of biological rhythms on serum lipids and lipoproteins and the effects of sex and age on the rhythms in a Brazilian hospital outpatient population.
  
  
  METHODS
  Retrospective laboratory study was carried out to evaluate the results of total cholesterol (TC), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C) and triglycerides (TG), from individuals registered at a university referral hospital over 8 years. The studied population was composed of individuals of both sexes and all ages totaling 38,579 participants and 301,934 measurements. Statistical analyses were carried out using the SAS program and the temporal analysis used the Cosinor method.
  
  
  RESULTS
  TG rhythm was present only in females. All other parameters were equally rhythmic in both sexes. Regarding age, HDL-C presented rhythms in all age groups, but TC and LDL-C showed seasonality only for those > 13 years, TG did not present rhythms in all age groups.
  
  
  CONCLUSIONS
  Effects of sex and age on biological rhythms detected in TC, LDL-C and HDL-C should be considered a significant cause of pre-analytical variation in these laboratory tests.
authors.affiliation: Department of Clinical Pathology, School of Medical Science of State University of Campinas, São Paulo, Brazil.
authors.forename: Fabio B
authors.initials: FB
authors.lastname: Dalpino
authors.forename: Luiz
authors.initials: L
authors.lastname: Menna-Barreto
authors.forename: Eliana C
authors.initials: EC
authors.lastname: de Faria
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D012727:Sex Characteristics
chemical_list: D008074:Lipoproteins