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Lifestyle and hypertension


It has long been known that restricting sodium intake and losing weight can result in reduced blood pressure. Do we just play lip service to this? Can interventions to help people accomplish these twin goals be effective in reducing the need for antihypertensive medicines? A new US study suggests that nonpharmacologic therapy in older persons can indeed reduce the need for antihypertensives [1].

Study

This was a complicated study. It involved 585 obese participants randomised to usual care, or sodium restriction, or weight loss, or both, and 390 non-obese participants randomised to usual care or salt restriction. All participants (mean age 67 years) had to have a systolic BP <145 mmHg and a diastolic BP <85 mmHg while being treated with a single antihypertensive medicine.

Participants received lots of help to achieve set goals reduction of salt intake to 80 mmol/day or less; weight loss of 4.5 kg or more), and to maintain them. The goal was to withdraw the antihypertensive medicine after three months of the intervention if blood pressure could be maintained at less than 150/90 over six weeks following withdrawal.

Outcome

Diagnosis of high blood pressure (>190/110 at a single visit) at one or more follow up visits, or treatment with antihypertensive, or a cardiovascular event during a median 29 months (range 15-36 months) of follow up.

Results

At the nine month follow up, 36% of the 443 participants assigned to sodium restriction and 11% of those assigned to usual care had urinary sodium of 80 mmol/day or less. The average fall of about 40 mmol/day was maintained over 30 months in participants assigned to sodium reduction.

Of those assigned to weight loss, 47% of 275 participants had losses of 4.5 kg or greater, compared with 13% of 260 not assigned. Over six to 30 months the average weight loss of 4 to 5 kg was maintained in the assigned group.

The majority of participants were able to have antihypertensive medicine withdrawn initially (Table).
Effect of sodium restriction and weight loss on withdrawal of antihypertensive medicine
Assignment Number Antihypertensive withdrawn No anti-hypertensive at 12 months No anti-hypertensive at 30 months
Percent
Usual care 147 87 32 16
Sodium restriction 144 93 56 36
Weight loss 147 93 54 35
Both 147 93 58 44
Thereafter the number declined, but even at 30 months after withdrawal there was a significantly greater number not taking antihypertensive medicine with either sodium restriction, or weight loss, and especially with both.

The figures imply a NNT for either sodium restriction or weight loss of 5, and for both sodium restriction and weight loss of 3 in obese participants.

Adverse effects


A number of strokes, transient ischaemic attacks and cardiovascular events occurred - with no differences between the groups, nor between different stages in the study. Sodium restriction was associated with a significant reduction in the rate of headaches.

Comment

Antihypertensive medicines in the elderly are effective ( Bandolier 15 ). The overall NNT to prevent one cardiovascular event was 18 (95% CI 14 to 25) patients to be treated for five years. To prevent coronary heart disease the NNT was 61 (39 to 141) and to prevent cerebrovascular disease the NNT was 43 (31 to 69).

Many patients might prefer not to take medicines which have adverse effects. The results of this study on sodium restriction and weight loss might encourage some of them to try nonpharmacological interventions first. Delivering the right advice and support will be a challenge, however.

Reference

  1. PK Whelton, LJ Appel, MA Espeland et al. Sodium reduction and weight loss in the treatment of hypertension of older persons. Journal of the American Medical Association 1998 279:839-46.



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