***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: A survey in 1994 showed that among the 20 % of the adult English population who were identified as hypertensive , ≈30 % had their blood pressures controlled to < 160 mm Hg systolic and < 95 mm Hg diastolic . The 1998 Health Survey for Engl and data up date the 1994 findings in light of new thresholds and targets for treatment outlined in recent national and international guidelines . This cross-sectional survey is analyzed to describe the prevalence , awareness , treatment , and control of hypertension in a r and om , nationally representative sample of 11 529 English adults ( ≥16 years ) living in noninstitutional households in 1998 and to compare these rates with those from 1994 . In 1998 , 20 % and 37 % of adults were hypertensive according to the old ( systolic ≥160 mm Hg or diastolic ≥95 mm Hg ) and new ( systolic ≥140 mm Hg or diastolic ≥90 mm Hg ) definitions , respectively . Corresponding values in 1994 were 20 % and 38 % . Treatment and control rates among hypertensive adults ( new definition ) improved from 26 % to 32 % and from 6 % to 9 % , respectively , although 60 % of those on treatment received only 1 antihypertensive drug in both years . Among persons with controlled hypertension , 59 % reported having  received nonpharmacological advice  from their physicians in 1998 compared with 30 % in 1994 . Rates of hypertension treatment and control have increased significantly ( P = 0.05 and P < 0.01 , respectively ) since 1994 but remain low by international st and ards . The 1998 data suggest that improved detection , greater use of nonpharmacological measures , and increased use of > 1 antihypertensive agent per patient would produce greater success in achieving target levels . This could lead to major reductions in fatal and nonfatal cardiovascular events Seventeen patients with a diastolic blood pressure over 90 mm Hg were recruited from a running health screening program  to participate in a double blind cross-over study of magnesium supplementation ( 15 mmol Mg2+/day ( Emgesan , Kabi Pharmacia ) for 3 weeks , followed by 30 mmol Mg2+/day for another 3 weeks , finishing with 40 mmol Mg2+/day for a final 3 weeks ) . A significant decrease in the mean systolic blood pressure was recorded from 154.0 + /- 10.7 mm Hg to 146.1 + /- 16.9 mm Hg ( P = .031 ) while the mean diastolic blood pressure decreased from 100.2 + /- 4.2 mm Hg to 92.0 + /- 6.6 mm Hg ( P = .0001 ) Phase I of the Trials of Hypertension Prevention ( TOHP ) was a r and omized , multicenter investigation that included double-blind , placebo-controlled testing of calcium and magnesium supplementation among 698 healthy adults ( 10.5 % blacks and 31 % women ) aged 30 to 54 years with high-normal diastolic blood pressure ( DBP ) ( 80 to 89 mm Hg ) . Very high compliance ( 94 to 96 % by pill counts ) with daily doses of 1 g of calcium ( carbonate ) , 360 mg of magnesium ( diglycine ) , or placebos was corroborated for the active supplements by significant net increases in all urine and serum compliance measures in white men and for urine compliance measures in white women . Overall , neither calcium nor magnesium produced significant changes in blood pressure at 3 and 6 months . Analyses stratified by baseline intakes of calcium , magnesium , sodium , or initial blood pressures also showed no effect of supplementation . These analyses suggested that calcium supplementation may have result ed in a DBP decrease in white women and that response modifiers in this subgroup might have included lower initial urinary calcium levels , urinary sodium levels , or lower body mass index . However , overall analyses indicated that calcium and magnesium supplements are unlikely to lower blood pressure in adults with high-normal DBP . The subgroup analyses , useful to formulate hypotheses , raise the possibility of a benefit to white women , which requires testing in future trials The main objective of this clinical trial was to evaluate the effects of magnesium pidolate ( 15 mmol/day ) on blood pressure at rest and during sympathetic stimulation induced by cold , isometric and tilt test ; peripheral blood flow has been evaluated by strain-gauge plethysmography . Fourteen mild to moderate hypertensives ( 8 males , 6 females , age range 40 - 60 years ) were r and omly given magnesium or placebo in a double-blind parallel clinical trial for 6 months . In the actively treated group magnesium urinary excretion increased from 5.3 + /- 2 to 7.7 + /- 2 mmol/24 h , and serum magnesium changed from 0.9 + /- 0.1 to 1.0 + /- 0.2 mmol/l . On magnesium , BP changed at rest from 156/97 + /- 12/4 to 149/90 + /- 8/3 mm Hg , during cold pressor test from 169/105 + /- 9/6 to 174/105 + /- 15/4 , during isometric exercise from 170/107 + /- 13/9 to 170/105 + /- 20/6 , and during tilt test from 149/96 + /- 11/6 to 153/96 + /- 17/7 mm Hg . Similar changes were observed in the placebo group . Peripheral resistances were 14.7 + /- 4 and 9.8 + /- 2 PRU before and after magnesium , respectively . These data indicate that long-term magnesium pidolate supplementation does not affect blood pressure at rest and during sympathetic stimulation , despite a slight , nonsignificant reduction in forearm peripheral resistance In a double-blind controlled trial , 91 middle-aged and elderly women with mild to moderate hypertension who were not on antihypertensive medication were r and omly assigned to treatment with magnesium aspartate-HCl ( 20 mmol Mg/d ) or placebo for 6 mo . Magnesium aspartate-HCl in the given dose was well-tolerated and was not associated with an increased frequency of diarrhea compared with placebo . At the end of the study , systolic blood pressure had fallen by 2.7 mm Hg ( 95 % CI -1.2 , 6.7 ; P = 0.18 ) and diastolic blood pressure by 3.4 mm Hg ( 1.3 , 5.6 ; P = 0.003 ) more in the magnesium group than in the placebo group . Blood pressure response was not associated with baseline magnesium status , as measured by dietary magnesium intake and urinary magnesium excretion . Urinary magnesium excretion in the magnesium group increased by 50 % during the intervention period . No changes were seen in other biochemical indexes , including serum concentrations of total and high-density-lipoprotein cholesterol . The findings suggest that oral supplementation with magnesium aspartate-HCl may lower blood pressure in subjects with mild to moderate hypertension Phase II of the Trials of Hypertension Prevention is a multicenter , r and omized , controlled trial design ed to determine the efficacy of weight loss and reduction of sodium intake for lowering blood pressure and incidence of hypertension among persons with high-normal levels of blood pressure . The 2 x 2 factorial study design includes weight loss alone , restricted sodium intake alone , the combination of weight loss and sodium restriction , and a control group .  Nine clinical centers used a variety of recruitment strategies to enroll 2382 participants over 17 months , which exceeded the sample size goal of 2250 . Among r and omized participants , 21 % were minorities and 34 % were women . Overall , direct mail generated the most r and omized participants ( 73 % ) , followed by community screening ( 12 % ) and media advertisement ( 11 % ) . Referrals from community health care providers yielded few participants . Prescreening improved overall efficiency and reduced costs . Participants who were more likely to drop out voluntarily during the three-visit screening regimen tended to be younger , single , male , smokers , and less educated OBJECTIVE To evaluate the impact of oral magnesium supplementation on risk factors for end-organ disease in patients with non-insulin-dependent diabetes mellitus ( NIDDM ) . DESIGN A 16-week r and omized , double-blind , placebo-controlled crossover trial . SETTING Outpatient center of an academic family medicine residency program . PATIENTS Twenty-eight patients ( age range , 28 to 84 years ; 57.1 % black ; 85.7 % women ) with NIDDM controlled by diet and /or an oral hypoglycemic , with a serum cholesterol levels over 5.20 mmol/L ( 200 mg/dL ) . INTERVENTION Following a 2-week placebo run-in period , each patient was r and omized to receive either sustained-release magnesium chloride ( Slo-Mag ) , 384 mg/d , or an identical-appearing placebo for 6 weeks . After a 2-week interim washout period , each patient was then treated with the alternative regimen for an additional 6-week period . MAIN OUTCOME MEASURES The systolic and diastolic blood pressure and levels of serum glucose , low-density and high-density lipoprotein and total cholesterol , triglycerides , and serum and total erythrocyte magnesium were measured at the beginning , midpoint , and end of each 6-week treatment phase . RESULTS Systolic blood pressure fell an average of 7.4 mm Hg ( P < .05 ) with treatment . There was no significant change in diastolic blood pressure or levels of serum glucose , low-density and high-density lipoprotein and total cholesterol , triglycerides , or serum and erythrocyte magnesium . CONCLUSIONS Oral magnesium supplementation in the doses and duration studied is modestly effective in reducing systolic blood pressure in patients with NIDDM but has little impact on other important biochemical parameters related to diabetes-associated end-organ disease Over the past few years , several trials on the effect of oral calcium supplementation on blood pressure have been undertaken both in normal subjects and in patients with high blood pressure . Of these , 15 r and omized , controlled studies were review ed : 10 included patients with high blood pressure , three studied normal subjects , and two used a low-calcium diet for comparison . The 15 studies review ed investigated a total of nearly 400 peoples . No significant evidence for a supine blood pressure-lowering effect of oral calcium supplementation was found in the trials as a whole or in those trials carried out in hypertensives only . However , a small effect on st and ing blood pressure was detected . Our study indicates that the overall effect of oral calcium on blood pressure , if any , is very small and confined to st and ing blood pressure , it is , therefore , inappropriate to recommend oral calcium supplementation for the treatment of essential hypertension The aim of this study was to evaluate if a nutritional dose of magnesium given orally changes the blood pressure in untreated hypertensive patients and if orally-given magnesium had any influence on serum and muscle magnesium and potassium . A r and omized , double-blind crossover study design was followed with magnesium 15 mmol/day or placebo treatment for two months . Thirty-nine patients aged 20 - 59 years , were treated . Sample s for magnesium and potassium in blood , muscle and urine were taken at entry time , after two months ( crossover time ) and after four months ( end of study ) . Systolic and diastolic supine and st and ing blood pressures were measured at the same times . No significant change in blood pressure , serum or muscle concentrations of electrolytes were observed on magnesium treatment . Urine magnesium rose significantly on magnesium , and it decreased significantly on placebo . Therefore results suggest that 15 mmol magnesium/day , given to untreated mild-to-moderate hypertensives does not alter blood pressure nor the concentrations of magnesium and potassium in serum and muscle , in patients with normal magnesium turnover To determine the impact of dietary patterns on the control of hypertension we studied the subgroup of 133 participants with systolic blood pressure ( BP ) of 140 to 159 mm Hg and /or diastolic BP of 90 to 95 mm Hg enrolled in the Dietary Approaches to Stop Hypertension ( DASH ) study . Participants were fed a control diet for a 3-week period and were then r and omized to receive for 8 weeks either the control diet ; a diet rich in fruits and vegetables , but otherwise similar to control ; or a combination diet rich in fruits , vegetables , and low-fat dairy products , including whole grains , fish , poultry , and nuts , and reduced in fats , red meats , sweets , and sugar-containing beverages .  Sodium intake and body weight were held constant throughout the study . The combination diet significantly reduced systolic BP ( -11.4 mm Hg , P < .001 ) and diastolic BP ( -5.5 mm Hg 
    Output:
    
Sub-group analyses and meta-regression indicated that heterogeneity between trials could not be explained by dose of magnesium , baseline blood pressure or the proportion of males among the participants .
This is because poor quality studies generally tend to over-estimate the effects of treatment .