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Low Cholesterol May Increase Mortality Risk In Over 70s

A DGReview of : " Cholesterol and all-cause mortality in elderly people from

the Honolulu Heart Program: a cohort study "

Lancet

08/02/2001

By Harvey McConnell

Low cholesterol rates in people over the age of 70 may increase and not

decrease their mortality risks.

" Our data accord with previous findings of increased mortality in elderly

people with low serum cholesterol, and show, for the first time, that

long-term persistence of low cholesterol concentration actually increases

risk of death, " declares Dr Irwin Schatz and colleagues at University of

Hawaii at Manoa, A. Bums School of Medicine, Honolulu, Hawaii.

" These data cast doubt on the scientific justification for lowering

cholesterol to very low concentrations (less than 4.65 mmol/L) in elderly

people. "

Dr Schatz and colleagues point out: " High concentration of total serum

cholesterol is known to be directly related to mortality in individuals aged

younger than 65 years. Previous clinical trials have not had large numbers

of patients aged older than 70 years, and researchers have been unable to

conclusively show this relation in elderly people. "

In a longitudinal population study, part of the Honolulu Heart Program, a

large epidemiological study of cardiovascular disease, the clinicians

studied fat and blood cholesterol concentrations of 3,572 Japanese/American

men who were aged 71-93 years in the early 1990s. They compared changes in

these concentrations over 20 years with all-cause mortality using three

different proportional hazards models.

Overall, average cholesterol concentrations decreased with increasing age of

individuals in the study population.

Individuals were divided into four quartiles according to blood cholesterol

concentrations: 1st quartile 2.09-4.32 mmol/L; 2nd quartile 4.33-4.86

mmol/L; third quartile 4.87-5.43mmol/L; fourth quartile 5.44-9.88 mmol/L.

Lower cholesterol concentration was associated with increased death rates;

age-adjusted mortality rates were 68.3, 48.9, 41.1, and 43.3 per 1, 000

population per year for the first to fourth quartiles of cholesterol

concentrations, respectively. Men in quartiles 2, 3, and 4 had reduced

death-rates of 28 percent, 40 percent , and 35 percent respectively compared

with men in the first (lowest cholesterol concentration) quartile.

Dr Schatz and colleague declare: " We have been unable to explain our

results. " But they speculate on the meanings.

Based on their data " the earlier that patients start to have lower

cholesterol concentrations, the greater the risk of death. Cholesterol

metabolism and homoeostatic mechanisms might differ in the very old (75

years), and little information is available about cholesterol-mortality

relations in this age group. "

Perhaps the data indicate a selective mortality; " those individuals who are

susceptible to biological effects of high serum cholesterol die before they

reach age 75 years. The individuals who are left would be a select group

with lower cholesterol and whose genetic makeup or other factors protect

them from the effects of higher cholesterol concentrations. "

To some degree, the clinicians continue, the Honolulu Heart Program data

support this hypotheses as there are few individuals with truly high

concentrations of cholesterol remaining in this population.

Dr Schatz and colleagues, in conclusion, raise two questions: " First, is

there a difference in biological effect from a permanent, untreated,

intrinsically low concentration of cholesterol when compared with the effect

in those who have a dietary or pharmacologically induced reduction of

cholesterol? As far as we are aware, this issue has not been addressed

scientifically.

" Second, in view of our data, and those of others, is there scientific

justification for attempts to lower cholesterol to concentrations below 4.65

mmol/L in elderly people " We believe that until more information about these

complex relations is available, prudence dictates a more conservative

approach in this age group. "

Lancet 2001; 358: 351-5. " Cholesterol and all-cause mortality in elderly

people from the Honolulu Heart Program: a cohort study "

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