Skip to main content
PMC home page
The BMJ logoLink to The BMJ
. 1991 Apr 6;302(6780):815–818. doi: 10.1136/bmj.302.6780.815

By how much does dietary salt reduction lower blood pressure? II--Analysis of observational data within populations.

C D Frost 1, M R Law 1, N J Wald 1
PMCID: PMC1669173  PMID: 2025704

Abstract

OBJECTIVE--To determine whether the estimates of the size of the association between blood pressure and sodium intake derived from studies of individuals within populations can be quantitatively reconciled with our estimates derived from comparisons of the average blood pressure and sodium intake between different populations. DESIGN--Examination of data from 14 published studies that correlated blood pressure recordings in individuals against measurements of their 24 hour sodium intake (within population studies). MAIN OUTCOME MEASURE--Comparison of observed differences in blood pressure per 100 mmol/24 h difference in sodium intake in each within population study with predicted differences calculated from the between population data, after allowing for the underestimation of the true association of blood pressure with sodium intake caused by the large day to day variation in 24 hour sodium intake within individuals. RESULTS--The underestimation bias inherent in the within populations studies reduced the regression slope of blood pressure on single measures of 24 hour sodium intake to between a half and a quarter of the true value (for example, in one study from 6.0 to 2.4 mm Hg/100 mmol/24 h). Estimates from between population comparisons of the regression slope of blood pressure on sodium intake, after adjustment to take this underestimation bias into account, were similar to the values actually observed in the within population studies. CONCLUSION--The within population studies confirm our estimates from between population comparisons of the magnitude of the association between blood pressure and sodium intake.

Full text

PDF

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Bulpitt C. J., Broughton P. M., Markowe H. L., Marmot M. G., Rose G., Semmence A., Shipley M. J. The relationship between both sodium and potassium intake and blood pressure in London Civil Servants. A report from the Whitehall Department of Environment Study. J Chronic Dis. 1986;39(3):211–219. doi: 10.1016/0021-9681(86)90026-3. [DOI] [PubMed] [Google Scholar]
  2. Connor S. L., Connor W. E., Henry H., Sexton G., Keenan E. J. The effects of familial relationships, age, body weight, and diet on blood pressure and the 24 hour urinary excretion of sodium, potassium, and creatinine in men, women, and children of randomly selected families. Circulation. 1984 Jul;70(1):76–85. doi: 10.1161/01.cir.70.1.76. [DOI] [PubMed] [Google Scholar]
  3. Elliott P., Forrest R. D., Jackson C. A., Yudkin J. S. Sodium and blood pressure: positive associations in a north London population with consideration of the methodological problems of within-population surveys. J Hum Hypertens. 1988 Aug;2(2):89–95. [PubMed] [Google Scholar]
  4. Kesteloot H., Huang D. X., Li Y. L., Geboers J., Joossens J. V. The relationship between cations and blood pressure in the People's Republic of China. Hypertension. 1987 Jun;9(6):654–659. doi: 10.1161/01.hyp.9.6.654. [DOI] [PubMed] [Google Scholar]
  5. Kesteloot H., Park B. C., Lee C. S., Brems-Heyns E., Claessens J., Joossens J. V. A comparative study of blood pressure and sodium intake in Belgium and in Korea. Eur J Cardiol. 1980 Mar;11(3):169–182. [PubMed] [Google Scholar]
  6. Law M. R., Frost C. D., Wald N. J. By how much does dietary salt reduction lower blood pressure? I--Analysis of observational data among populations. BMJ. 1991 Apr 6;302(6780):811–815. doi: 10.1136/bmj.302.6780.811. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Law M. R., Frost C. D., Wald N. J. By how much does dietary salt reduction lower blood pressure? III--Analysis of data from trials of salt reduction. BMJ. 1991 Apr 6;302(6780):819–824. doi: 10.1136/bmj.302.6780.819. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Liu K., Cooper R., McKeever J., McKeever P., Byington R., Soltero I., Stamler R., Gosch F., Stevens E., Stamler J. Assessment of the association between habitual salt intake and high blood pressure: methodological problems. Am J Epidemiol. 1979 Aug;110(2):219–226. doi: 10.1093/oxfordjournals.aje.a112806. [DOI] [PubMed] [Google Scholar]
  9. Liu L. S., Zheng D. Y., Jin L., Liao Y. L., Liu K., Stamler J. Variability of urinary sodium and potassium excretion in north Chinese men. J Hypertens. 1987 Jun;5(3):331–335. doi: 10.1097/00004872-198706000-00011. [DOI] [PubMed] [Google Scholar]
  10. Luft F. C., Aronoff G. R., Sloan R. S., Fineberg N. S. Intra- and interindividual variability in sodium intake in normal subjects and in patients with renal insufficiency. Am J Kidney Dis. 1986 May;7(5):375–380. doi: 10.1016/s0272-6386(86)80085-3. [DOI] [PubMed] [Google Scholar]
  11. Siani A., Iacoviello L., Giorgione N., Iacone R., Strazzullo P. Comparison of variability of urinary sodium, potassium, and calcium in free-living men. Hypertension. 1989 Jan;13(1):38–42. doi: 10.1161/01.hyp.13.1.38. [DOI] [PubMed] [Google Scholar]
  12. Smith W. C., Crombie I. K., Tavendale R. T., Gulland S. K., Tunstall-Pedoe H. D. Urinary electrolyte excretion, alcohol consumption, and blood pressure in the Scottish heart health study. BMJ. 1988 Jul 30;297(6644):329–330. doi: 10.1136/bmj.297.6644.329. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Staessen J., Bulpitt C., Fagard R., Joossens J. V., Lijnen P., Amery A. Four urinary cations and blood pressure. A population study in two Belgian towns. Am J Epidemiol. 1983 Jun;117(6):676–687. doi: 10.1093/oxfordjournals.aje.a113601. [DOI] [PubMed] [Google Scholar]
  14. Strazzullo P., Trevisan M., Farinaro E., Cappuccio F. P., Ferrara L. A., de Campora E., Mancini M. Characteristics of the association between salt intake and blood pressure in a sample of male working population in southern Italy. Eur Heart J. 1983 Sep;4(9):608–613. doi: 10.1093/oxfordjournals.eurheartj.a061532. [DOI] [PubMed] [Google Scholar]
  15. Watt G. C., Foy C. J. Dietary sodium and arterial pressure: problems of studies within a single population. J Epidemiol Community Health. 1982 Sep;36(3):197–201. doi: 10.1136/jech.36.3.197. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from BMJ : British Medical Journal are provided here courtesy of BMJ Publishing Group

RESOURCES