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Hypertension and weight loss

Study
Results
Comment
Bandolier is interested in how lifestyle can keep people out of the hands of the healthcare system. It is better for individuals and better for healthcare systems. Being overweight is a bad thing for many reasons, one of which is that obesity is associated with high blood pressure. Bandolier 51 reported that weight loss and salt restriction could result in patients on antihypertensive medicines not needing to use them. Another large RCT now reinforces this message, emphasising that losing weight reduces blood pressure and helps stop people becoming patients [1].

Study


There were just under 1200 participants. They were overweight, with a body mass index of 25 to 37 (mean 31), and with a mean weight of 99 kg for men and 84 kg for women. They took exercise only once or twice a week, and their mean systolic blood pressure was 127 mmHg and diastolic 86 mmHg. None was being treated for hypertension at the start of the trial, or for diabetes, renal disease, or cardiovascular disease. Their mean age was 43 years.

Randomisation was to weight loss or usual care. Weight loss had a target of 4.5 kg during the first six months, maintained over a further 30 months. Individual counselling sessions were followed by 14 group meetings, and thereafter six bi-weekly sessions, and then monthly sessions. Other options were available after 18 months. Behavioural self-management was the intention, with monitoring with food and activity diaries. Dietary interventions focused on reducing fat, sugar and alcohol consumption. The target was a caloric intake that allowed individuals to lose weight, but loss of more than 0.9 kg a week was discouraged. Weight and blood pressure were recorded every six months, by staff blinded to treatment assignment. Follow up was over 90%.

Results


The control group of 596 patients gradually increased their mean weight by just under 2 kg over 36 months. The intervention group lost an average of 4.4 kg over the first six months, but weight gradually increased so that by 36 months the mean was just 0.2 kg below the starting weight, but 2 kg below the control group.

The intervention group had a mean reduction in systolic blood pressure of 2.7 mmHg below control at six months, and 0.9 mmHg at 36 months.

Blood pressure was highly related to the extent and duration of weight loss. For instance, blood pressure at 36 months was very much lower in those who achieved and maintained a weight loss of at least 4.4 kg, whereas it was minimally reduced or even increased in those with no weight loss or who actually gained weight (Figure).

Figure: Mean change in blood pressure by quintiles of weight loss at 36 months



  • In those whose weight loss at six and 36 months was 2.5 kg or less, there was no change in blood pressure.
  • In those who initially lost 4.5 kg or more at six months, but whose weight loss at 36 months was less than 2.5 kg, initial blood pressure reductions had not been maintained.
  • In those who had lost at least 4.5 kg by six months and maintained that loss, an initial average fall in systolic and diastolic blood pressure of 8 or 9 mmHg was maintained.

Weight loss also prevented the onset of hypertension defined as a systolic blood pressure of at least 140 mmHg, a diastolic blood pressure of 90 mmHg, or prescription of antihypertensive medicines. The risk ratios (all we are given) were significantly below 1 for the intervention compared to the control group. For successfully maintained weight loss compared to controls, the risk ratio was 0.35 (95% CI 0.2 to 0.6).

Comment


There was a direct dose-response relationship. Lose more weight and keep it off, and your blood pressure will fall more and the fall will be maintained longer. This is important information for a relatively young (43 years) but overweight and unfit group of people without established hypertension. The lesson is that without action they will gain more weight, their blood pressure will rise, and they will need antihypertensive medicines.

That's not always a good thing, because effective though they may be, efficacy comes with a price. Without feeling much different one goes from being a person to being a patient. The medicines have adverse effects, and those are problematical for many people.

Weight loss plus exercise is a good way of preventing this. Another good example of the benefits of healthy living. The question is one of delivery. Perhaps we need to have a little health economic modelling to demonstrate the personal and societal benefits of putting more effort into delivering a health service rather than a sick service.

References:

  1. VJ Stevens et al. Long-term weight loss and changes in blood pressure: results of the trials of hypertension prevention, phase II. Annals of Internal medicine 2001 134: 1-11.
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