Irwin J Schatz, Kamal Masaki, Katsuhiko Yano, Randi Chen, Beatriz L Rodriguez, J David Curb
A generally held belief is that cholesterol concentrations should be kept low to lessen the risk of cardiovascular disease. However, studies of the relation between serum cholesterol and all-cause mortality in elderly people have shown contrasting results. To investigate these discrepancies, we did a longitudinal assessment of changes in both lipid and serum cholesterol concentrations over 20 years, and compared them with mortality.
Lipid and serum cholesterol concentrations were measured in 3572 Japanese/American men (aged 71–93 years) as part of the Honolulu Heart Program. We compared changes in these concentrations over 20 years with all-cause mortality using three different Cox proportional hazards models.
Mean cholesterol fell significantly with increasing age. Age-adjusted mortality rates were 68·3, 48·9, 41·1, and 43·3 for the first to fourth quartiles of cholesterol concentrations, respectively. Relative risks for mortality were 0·72 (95% CI 0·60–0·87), 0·60 (0·49–0·74), and 0·65 (0·53–0·80), in the second, third, and fourth quartiles, respectively, with quartile 1 as reference. A Cox proportional hazard model assessed changes in cholesterol concentrations between examinations three and four. Only the group with low cholesterol concentration at both examinations had a significant association with mortality (risk ratio 1·64, 95% CI 1·13–2·36).
We have been unable to explain our results. These data cast doubt on the scientific justification for lowering cholesterol to very low concentrations (less than 4·65 mmol/L) in elderly people.