Abstract Background Dietary recommendations for the public are often adopted as guidelines for patients diagnosed with cardiovascular disease (CVD), yet it remains unclear if the underlying evidence is generalisable to this patient group. Purpose To systematically review and meta-analyse the evidence of healthy dietary patterns with all-cause and CVD mortality, and recurrent CVD events in CVD patients. Methods Medline, Embase, Web of Science and the Cumulative Index to Nursing and Allied Health Literature were searched up to May 26, 2022 for randomised controlled trials (RCTs) with ≥6 months of follow-up and prospective cohort studies. Summary relative risks (RR) and 95% confidence intervals (95%CI) were calculated using random-effects meta-analysis. Study quality was assessed with Cochrane risk of bias tools (RoB 2 for RCTs and ROBINS-E for cohorts). Results Of 28,291 abstracts, 41 articles met inclusion criteria, including 19 articles from 14 unique RCTs and 22 cohort studies. RCTs were conducted between 1956 and 2020, had a median duration of 3.3±2.6y and enrolled 14,065 CVD patients, of whom 84% were men, with a median age of 56±5y. Among 15 comparisons across 14 RCTs, 4 focused on fat replacement, 3 on the Mediterranean diet, 2 on low-fat diets, 2 on combined low-fat/low sodium diets, and 2 on high fibre diets, all compared to minimal or no dietary advice. No significant effects of any dietary intervention were found for all-cause mortality, CVD mortality, recurrent CVD, and coronary revascularisation. Between-study heterogeneity (I2= 34-60%) was partly explained by geographical location for all outcomes and intervention diet for CVD mortality. Stratified meta-analysis by intervention diet showed that a Mediterranean diet significantly reduced CVD mortality (RR: 0.40; 95%CI: 0.19,0.83, I2:14%). Prospective cohort studies were published after 2002 with dietary data from 1976 to 2017. Patients had a median age of 65±5y of whom 67% were men and had a median follow-up of 6.7±4.3y. Twenty-two cohorts (104,386 CVD patients) primarily assessed the Mediterranean diet (60%). Compared to those with low adherence, patients with study-specific highest adherence to any healthy dietary pattern had a 29% lower all-cause mortality (0.71; 0.65, 0.78), 25% lower CVD mortality (0.75; 0.66, 0.84), and a 17% lower recurrent CVD incidence (0.83; 0.75, 0.92). Significant heterogeneity was observed (I2: 49-76%), explained by geographical location, average age, sex, CVD diagnosis, follow-up duration, but not by type of healthy dietary pattern. No significant associations were found for recurrent CVD. Studies were predominantly classified as of some concerns (65% RCTs) or high risk (52% cohorts) Conclusions A healthy dietary pattern, like the Mediterranean diet, likely benefits secondary prevention of CVD. Due to considerable between-study heterogeneity and bias risk, well-conducted future studies are needed using clearly defined diets to strengthen the evidence.
Griep et al. (Sat,) studied this question.