High density lipoprotein and apolipoprotein A-i during physical inactivity. Demonstration at low levels in patients with spine fracture.

Lack of physical activity appears to have deleterious effects on serum lipoproteins. Twenty-three patients who were completely immobilised by traumatic fracture of the spine had significantly lower (P < 0.001) plasma high density lipoprotein cholesterol (HDL-C) and apolipoprotein A-I levels than normally mobile paired control subjects. The low density lipoprotein cholesterol (LDL-C) levels of the immobile patients were not different from those of controls but the LDL triglyceride (LDL-TG) of the patients was increased. The patients had a significantly higher LDL/HDL-C ratio and HDL-C/apoprotein A-I ratio than the controls. These results suggest that the increased risk of ischemic heart disease in physically inactive people is partially accounted for by low plasma HDL levels. On the other hand, caution is needed in the interpretation of HDL findings in clinical conditions where the physical activity of the patients is limited.