The level at which blood pressure should be treated.

The large multicenter trials of treatment in mild to moderate hypertension have shown unequivocally that the risk of stroke is reversed. The impact of treatment on ischemic heart disease is more debatable. Since there is no discontinuity in the risk of different levels of blood pressure, any advice about the level of pressure to treat must be arbitrary. The British Hypertension Society Guidelines recommend a sustained diastolic pressure of 100 mmHg or more over a 3- to 4-month period. This empirical advice is based upon subgroup analysis of the MRC and Australian Therapeutic Trials that suggests most of the benefit in treating the mildest degrees of hypertension occur in this group of patients. The role of newer classes of agent, such as ACE inhibitors or calcium-channel blockers, cannot be fully assessed in the absence of proper end-point trials. Whilst reasons for using these agents as first-line therapy have been put forward, these remain speculative in the absence of such trials. The much greater cost of newer agents in the context of universally cost-constrained health services also has to be borne in mind before recommending their widespread use as first-line therapy.