Relation between circadian patterns in levels of circulating lipoprotein(a), fibrinogen, platelets, and related lipid variables in men

Background A correlation has been reported between lipoprotein(a) [Lp(a)] c oncentration and risk for coronary artery disease. High concentrations of L p(a) might be markers for vascular or tissue injury or might be associated with other genetic or environmental factors that can cause acute myocardial infarction. Methods We measured the circadian characteristics of circulating Lp(a), fib rinogen, platelets, cholesterol, triglycerides, high-density lipoprotein ch olesterol, and low-density lipoprotein cholesterol for a group of adult mal e volunteers who had no clinical symptoms. We obtained samples every 3 hour s around the clock to assess the normal degree of variation within a 24 hou r period and to test for similarities in circadian patterns and correlation s with level of Lp(a). Results Each variable displayed a highly significant circadian rhythm. Lp(a ), fibrinogen, high-density lipoprotein cholesterol, and low-density lipopr otein cholesterol peaked in the morning. Cholesterol and platelets peaked i n the late afternoon, and triglycerides peaked in the evening. Conclusions Although peak levels of Lp(a) and fibrinogen coincide with repo rted morning peak frequencies of myocardial infarction and stroke, the plat elet peak appears to coincide with late afternoon peak frequencies of sudde n cardiac death and fatal stroke. The data suggest that proper timing of si ngle samples may improve the usefulness and accuracy of diagnosis, risk ass essment, and therapy.