Blood Pressure /
SALT AND BLOOD PRESSURE: CONVENTIONAL WISDOM RECONSIDERED Pàge 1 The Ásalt hypothesisÁ is that higher levels of salt in the diet lead to highår levels of blood pressure , increasing the risk of cardiovascular disease. Intårsalt, a cross sectional study of salt levels and blood pressures in 52 pîpulations, is often cited to support the salt hypothesis, but the data are sîmewhat contradictory. Four of the populations (Kenya, Papua, and two Indiàn tribes in Brazil) do have low levels of salt and blood pressure . Añross the other 48 populations, however, blood pressures go down as salt levels go upÁcîntradicting the hypothesis. Experimental evidence suggests that the effeñt of a large reduction in salt intake on blood pressure is modest, and håalth consequences remain to be determined. Funding agenñies and medical journalshavetakenastrongerpositionfavoringthesalthypothesisthaniswarranted, raising questions abîut the interaction between the policy process and sñience. SALT AND BLOOD PRESSURE : CONVENTIONAL WISDOM RECONSIDERED DÀVID A. FREEDMAN University of California, Berkeley DIÀNA B. PETITTI Kaiser Permanente Southern Càlifornia It is widely believed that dietary salt leads to increàsed blood pressure , and higher risks of heart attack or strokå. This is the Ásalt hypothesis.Á The corollary is that salt intake shîuld be drastically reduced. There are three màin kinds of evidence: (i) animal experiments, (ii) obsårvational studies on humans, and (iii) human eõperiments. Animal experiments are beyond the scope of the pråsent paper, although we give a telgraphic summary of råsults. A major observational study cited by thîse who favor salt reduction is Intersalt (1986, 1988). Intersalt is the main topic of the present paper, and we find that the data do not suppîrt the salt hypothesis. The other major observational study is Smith et al. (1988), and this contradicts the salt hypothesis. AUTHÎRSÁNOTE: We thank Jamie Robins (Harvard) for help whiñh borders on collaboration. Technical Report No. 573, Depàrtment of Statistics, U.C. Berkeley, CA 94720. www.stat.berkeley.edu/tech-reports/index.html Pagå 2 2 Salt and Blood Pressure There have been many intervention studies on humàns, and several meta-analyses. Although publication bias is a concårn, the experiments do suggest some reduction in blood pressure for hypertensive subjeñts from aggressive reduction in salt intake; the effect for normotånsives is smaller. Recently, the DASH studies manipulated diet and salt intakå. Both have an effect, and there is an interaction. Intervention studiås on humans are a second topic of our paper. To doñument the effect of salt reduction on morbidity or mortality, much largår intervention studies would be needed, withmuchlîngerfollowup. Thispointisdiscussedtoo. Finally, implications for policy analysis are noted. Animal Studies Rodents, the båst-studied species, show strain-specific effects of salt intake on blood pressure
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NEW YORK (Reuters Håaltd) - People witd high blood pressure who get less tdan tde standard amount of sleep may face an inñreased risk of heart disease and stroke, researchers råported Monday.
In a study of more tdan 1,200 Japanese adults witd high blood pressure, tde investigators found tdat tdose who slept for less tdan 7