Research

Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP)

BMJ 2007; 334 doi: 10.1136/bmj.39147.604896.55 (Published 26 April 2007)
Cite this as: BMJ 2007;334:885
  1. Nancy R Cook, associate professor1,
  2. Jeffrey A Cutler, former senior scientific adviser2,
  3. Eva Obarzanek, research nutritionist2,
  4. Julie E Buring, professor1,
  5. Kathryn M Rexrode, assistant professor of medicine1,
  6. Shiriki K Kumanyika, professor of epidemiology3,
  7. Lawrence J Appel, professor of medicine4,
  8. Paul K Whelton, president and chief executive officer5
  1. 1Brigham and Women's Hospital, Harvard Medical School, Boston, MA
  2. 2National Heart, Lung, and Blood Institute, Bethesda, MD
  3. 3University of Pennsylvania School of Medicine, Philadelphia, PA
  4. 4Johns Hopkins University, Baltimore, MD
  5. 5Loyola University Health System, Maywood, IL
  1. Correspondence to: N Cook ncook{at}rics.bwh.harvard.edu
  • Accepted 7 February 2007

Abstract

Objective To examine the effects of reduction in dietary sodium intake on cardiovascular events using data from two completed randomised trials, TOHP I and TOHP II.

Design Long term follow-up assessed 10-15 years after the original trial.

Setting 10 clinic sites in 1987-90 (TOHP I) and nine sites in 1990-5 (TOHP II). Central follow-up conducted by post and phone.

Participants Adults aged 30-54 years with prehypertension.

Intervention Dietary sodium reduction, including comprehensive education and counselling on reducing intake, for 18 months (TOHP I) or 36-48 months (TOHP II).

Main outcome measure Cardiovascular disease (myocardial infarction, stroke, coronary revascularisation, or cardiovascular death).

Results 744 participants in TOHP I and 2382 in TOHP II were randomised to a sodium reduction intervention or control. Net sodium reductions in the intervention groups were 44 mmol/24 h and 33 mmol/24 h, respectively. Vital status was obtained for all participants and follow-up information on morbidity was obtained from 2415 (77%), with 200 reporting a cardiovascular event. Risk of a cardiovascular event was 25% lower among those in the intervention group (relative risk 0.75, 95% confidence interval 0.57 to 0.99, P=0.04), adjusted for trial, clinic, age, race, and sex, and 30% lower after further adjustment for baseline sodium excretion and weight (0.70, 0.53 to 0.94), with similar results in each trial. In secondary analyses, 67 participants died (0.80, 0.51 to 1.26, P=0.34).

Conclusion Sodium reduction, previously shown to lower blood pressure, may also reduce long term risk of cardiovascular events.

Footnotes

  • We thank David Gordon, Jean MacFadyen, and their staff at the TOHP coordinating centre for their efforts in conducting the follow-up study.

  • Contributors: NRC had primary responsibility for designing, conducting, analysing, interpreting, and reporting data from the follow-up study. JAC, EO, JEB, KMR, and PKW contributed to the design and conduct of the study, and all authors assisted in the interpretation of study results and critical revision of the manuscript. NRC is guarantor.

  • Funding: TOHP I and II were supported by cooperative agreements HL37849, HL37852, HL37853, HL37854, HL37872, HL37884, HL37899, HL37904, HL37906, HL37907, and HL37924, and the TOHP follow-up study was supported by grant HL057915, all from the National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD.

  • Competing interests: None declared.

  • Ethical approval: Institutional review boards of each participating centre approved the study.

  • Accepted 7 February 2007

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