Seasonal variations in serum lipid and apolipoprotein levels evaluated by periodic regression analyses

Periodic regression analyses have been employed in a study of the variations in serum lipoprotein variables in 12 men during 12 months. The monthly means in the A-II polypeptide (A-II) and apolipoprotein B (apoB) varied significantly with time according to sine curves. Maxima of +5 and +8% from the annual averages were observed for A-II and apoB, respectively, during the winter months, whereas minima of -5 and -8%, respectively, occurred during summer. There were considerable individual differences in amplitude and phase in serum cholesterol, alpha-lipoprotein cholesterol and apolipoprotein A-I (apoA-I), whereas the variations in monthly means of the whole group were not significant. Storage of sera at -85 degrees C for 1 yr seems not to have influenced the results of determinations of serum cholesterol and triglycerides, apoA-I, and A-II, but may have caused differences observed in apoB between the two months of May 1978 and 1979.