QuestionWhat is the effectiveness and cost effectivenesss of adopting a low fat diet, versus no change in fat intake, to improve outcome in people at high risk of cardiovascular disease?

Grading:1+Well-conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias
Reference number 395
Hjerkinn EM;Sandvik L;Hjermann I;Arnesen H;Hjerkinn EM;Sandvik L;Hjermann I;Arnesen H;
Effect of diet intervention on long-term mortality in healthy middle-aged men with combined hyperlipidaemia
2004J Intern Med255 1pgs 68 73
Study Type:Randomised Controlled Trial
Patient CharacteristicsThis was a subgroup analysis of men, aged 40–49 (in 1972) from city of Oslo. The subjects were a sub-sample of 104 individuals (49 control, 55 intervention) selected for a previous study: 1232 healthy working men were selected according to the following criteria (Hjermann 1981): Mean serum cholesterol 7.5–9.8mmol/L, coronary risk scores (based on cholesterol, smoking & BP) in upper quartile of distribution & systolic BP < 150mmHg. Exclusion criteria: CVD, diabetes, elevated blood sugar (>7.5mmol/L), cancer, disabling disease, psychopathological disease or alcoholism. The sub-sample of 104 were further selected for the present trial if fasting triglycerides > 2.5mmolL. Baseline: control group & intervention in brackets: age 46+/−3 (46+/−3) years, total cholesterol fasting 7.9+/−0.6mmolL(7.9+/− 0.6mmol), fasting triglycerides. 4.0+/− 1.9mmolL (3.5+/−1.0), BMI 26.8+/−2.9 (26.0+/−2.9), smoking 73% (65%)
Interventionsdietary: reduction in total energy intake (reduction in sat fat & slight increase in polyunsaturated fat). Smoking: anti-smoking advice given to intervention group.
Comparisonsmortality - diet vs. control groups, but diet group also received anti-smoking advice. Numbers of smokers in each group at start of study has been taken into account.
Study Length5 years then follow up at 19 years.
OutcomesMortality (included CVD, cancer & other causes), Total cholesterol, fasting triglycerides, BMI
EffectAverage relative change (compared to baseline measurements) in: control group: total cholesterol (3.8% decrease), fasting triglycerides (−13.5%), BMI (+0.8%) & intervention group: Total cholesterol −10.5%, P=0.011, Fasting Triglycerides −27.2%, P=0.049, BMI −4.0, P<0.001. For the outcome of % mortality: 42% for control & 21.8% intervention. University analysis diet vs. control for mortality: RR=0.49, 95% CI 0.22–0.91, P=0.022. This difference remained significant when adjusted for age & smoking status using a Cox regression analysis: RR = 0.47.95% CI 0.23–0.96, P=0.038. Statistical analysis did not, however, distinguish between different types of mortality (Diet group: 12 deaths out of 55 (6 CVD, 4 cancer, 2 other) & Control group: 21 deaths out of 49 (11 CVD, 8 cancer & 2 other) i.e. in the diet group, 10.9% of subjects died of CVD & in control, 22.5% died of CVD so mortality due to CVD was 48.4% lower in the diet group.
Fundingnorweigan cardiovascular council & norweigan retail company RIMI
ConclusionsOur question asks whether a low fat diet is effective (vs. no change in diet) to improve outcome in people of high CVD risk. The study investigated the effects of a dietary intervention (reduction in sugar, alchohol & fat) on mortality in healthy men aged 40–49 years at increased risk of CHD (normotensive, non-diabetic, no CVD but hypercholesterolaemia & hypertriglyceridaemia). The study found mortality to be 51% lower in the intervention group over a 24 year period (control group % mortality = 42.9, diet group, = 21.8) RR=0.49, 95% CI 0.22–0.91, P=0.022 in univariate analysis & this difference remained significant when adjusted for age & smoking status (RR = 0.47, 95% CI 0.23–0.96, P=0.038).
Quality+subjects in the intervention group were also given anti-smoking advice, however, a five year follow up of numbers of smokers showed this advice did not have a significant effect on the number of smokers in the intervention group compared with control.

From: Appendix D, Clinical Evidence Extractions

Cover of Lipid Modification
Lipid Modification: Cardiovascular Risk Assessment and the Modification of Blood Lipids for the Primary and Secondary Prevention of Cardiovascular Disease [Internet].
NICE Clinical Guidelines, No. 67.
National Collaborating Centre for Primary Care (UK).
Copyright © 2008, Royal College of General Practitioners.

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