Monthly and seasonal variation in plasma lipids in healthy Australian men: a longitudinal study in Melbourne

A prospective study of seasonal variability of lipids in 36 healthy men, aged 40-45 years, over 14 months in Melbourne showed significant monthly and seasonal variation by paired t-test. Measurement of cholesterol and triglycerides was carried out by standard, automated enzymic assays calibrated with CDC certified materials. High Density Lipoprotein Cholesterol (HDLC) was measured after Polyethylene Glycol 6000 precipitation of Apo B containing lipoproteins. Intra-individual variation ranged wisely; Cholesterol: mean Coefficient of Variation (CV) 6.9%, range 4.1 to 14.0, HDLC: mean CV 9.1%, range 5.3 to 15.6 Low Density Lipoprotein Cholesterol (LDLC): mean CV 10.2%, range 5.2 to 18.4. The seasonal effect showed the most favourable lipid/ lipoprotein profile, ie lowest total and LDLC, highest HDLC to occur in the antipodean summer (Nov/Dec) and the least favourable profile in winter (Jul/Aug), with highest (total) Cholesterol and lowest HDLC. This is best observed as the LDLC/HDLC ratio which peaks in July (3.6), with the trough in December (2.7). This pattern is consistent with seasonal effects described previously in the northern hemisphere, except that the months are reversed. Weight did not alter significantly during the period of the study. Seasonal and individual variation in lipids and lipoproteins should be taken into account in the clinical management of lipid disorders.