Biochemical measures in a population-based study: effect of fasting duration and time of day

Background: Epidemiological studies generally aim to make simple but unbiased measurements of individuals. For this reason measurements of metabolic variables (including blood lipids, glucose and insulin) are usually carried out after a period of fasting. Few studies have examined the extent to which the use of a defined protocol for fasting in epidemiological studies abolishes the influence of fasting duration and time of day on biochemical measurements. Methods: Cross-sectional survey of British Regional Heart Study participants (4252 men aged 60-79 years), in which men without diabetes were asked to provide a blood sample after fasting for at least 6 h. Serum total, HDL and LDL cholesterol, triglyceride and insulin, and plasma glucose concentrations were measured between 08:00 h and 18:00 h. Results: Non-fasting men had lower mean LDL cholesterol and higher glucose, insulin and triglyceride levels than fasting men; these differences were more marked among diabetics. Among fasting men without diabetes, insulin and glucose levels were strongly related to time of day, falling gradually throughout the morning and remaining stable in the afternoon. Because of these relationships and the dependence of fasting duration on time of day, insulin and glucose displayed a periodic relation with fasting duration above 6 h. These associations were largely abolished by adjustment for time of day; associations with time of day were unaffected by adjustment for fasting duration. Triglyceride concentrations fell with increasing fasting duration. This relationship was also mediated through a gradual increase in triglyceride levels throughout the day. Adjustments to compensate for these variations are described. Discussion: Even after fasting, biochemical measurements may still differ in relation to fasting duration and time of day. In epidemiological studies, it is important to standardize both the period of fasting and the time of day as much as possible, and make adjustments where necessary.

[1]  R. Troisi,et al.  Diurnal variation in fasting plasma glucose: implications for diagnosis of diabetes in patients examined in the afternoon. , 2000, JAMA.

[2]  P. Whincup,et al.  Twenty year follow-up of a cohort based in general practices in 24 British towns. , 2000, Journal of public health medicine.

[3]  L. Morgan,et al.  Diurnal Variations in Peripheral Insulin Resistance and Plasma Non-Esterified Fatty Acid Concentrations: A Possible Link? , 1999, Annals of clinical biochemistry.

[4]  A J Scheen,et al.  Roles of circadian rhythmicity and sleep in human glucose regulation. , 1997, Endocrine reviews.

[5]  K. Uekama,et al.  Direct measurement of high-density lipoprotein cholesterol in serum with polyethylene glycol-modified enzymes and sulfated alpha-cyclodextrin. , 1995, Clinical chemistry.

[6]  M. Marmot,et al.  Gender and employment grade differences in blood cholesterol, apolipoproteins and haemostatic factors in the Whitehall II study. , 1993, Atherosclerosis.

[7]  M. Røder,et al.  Enzyme immunoassay for intact human insulin in serum or plasma. , 1993, Clinical chemistry.

[8]  P. Elwood,et al.  Plasma triglyceride and high density lipoprotein cholesterol as predictors of ischaemic heart disease in British men , 1992, British heart journal.

[9]  R N Bergman,et al.  Diurnal Variation in Glucose Tolerance: Cyclic Suppression of Insulin Action and Insulin Secretion in Normal-Weight, But Not Obese, Subjects , 1992, Diabetes.

[10]  J. Levy,et al.  Understanding "insulin resistance": both glucose resistance and insulin resistance are required to model human diabetes. , 1991, Metabolism: clinical and experimental.

[11]  K. Polonsky,et al.  Nocturnal elevation of glucose levels during fasting in noninsulin-dependent diabetes. , 1991, The Journal of clinical endocrinology and metabolism.

[12]  E. van Cauter,et al.  Nocturnal decrease in glucose tolerance during constant glucose infusion. , 1989, The Journal of clinical endocrinology and metabolism.

[13]  M. Walker,et al.  Diurnal variations in serum biochemical and haematological measurements. , 1989, Journal of clinical pathology.

[14]  W. Gruber,et al.  Reagent for the Enzymatic Determination of Serum Total Triglycerides with Improved Lipolytic Efficiency , 1984, Journal of clinical chemistry and clinical biochemistry. Zeitschrift fur klinische Chemie und klinische Biochemie.

[15]  T. M. Hayes,et al.  Determinants of plasma lipoproteins and coagulation factors in men from Caerphilly, South Wales. , 1983, Journal of epidemiology and community health.

[16]  J. Ziegenhorn,et al.  Reagent for the enzymatic determination of serum total cholesterol with improved lipolytic efficiency. , 1983, Clinical chemistry.

[17]  S J Pocock,et al.  British Regional Heart Study: cardiovascular risk factors in middle-aged men in 24 towns. , 1981, British medical journal.

[18]  P. Zimmet,et al.  Diurnal Variation in Glucose Tolerance: Associated Changes in Plasma Insulin, Growth Hormone, and Non-esterified , 1974, British medical journal.

[19]  H. Keen,et al.  Cardiorespiratory disease and diabetes among middle-aged male Civil Servants. A study of screening and intervention. , 1974, Lancet.

[20]  P. Trinder.  Determination of Glucose in Blood Using Glucose Oxidase with an Alternative Oxygen Acceptor , 1969 .

[21]  P. Kuo,et al.  Dietary fats and the diurnal serum triglyceride levels in man. , 1959, The Journal of clinical investigation.