In primary prevention , the association of BP-lowering treatment with major cardiovascular events was dependent on baseline systolic BP ( SBP ) .
Conclusions and Relevance Primary preventive BP lowering is associated with reduced risk for death and CVD if baseline SBP is 140 mm Hg or higher .
At lower BP levels , treatment is not associated with any benefit in primary prevention but might offer additional protection in patients with CHD
Importance High blood pressure ( BP ) is the most important risk factor for death and cardiovascular disease ( CVD ) worldwide .
The optimal cutoff for treatment of high BP is debated .
Objective To assess the association between BP lowering treatment and death and CVD at different BP levels .
The Australian Therapeutic Trial in Mild Hypertension.
In the Australian Therapeutic Trial in Mild Hypertension treated patients had significantly lower cardiovascular mortality and a significantly lower incidence of cerebrovascular complications than patients given placebos .  There was , however , no difference in the incidence of nonfatal myocardial infa rct ion or other new manifestations of ischaemic heart disease . Although the evidence of benefit from treatment was clear-cut , the number of cardiovascular complications in the control group was small . This was due to several factors . Patients admitted to the trial had no preceding evidence of cardiovascular complications  , the blood pressure fell spontaneously to below 95 mm Hg in almost half the control group , and patients whose blood pressures rose to levels above 110 mm Hg were given treatment , but remained in the placebo group for analysis . In both treated and placebo groups , trial end-points occurred more frequently in persons whose average diastolic blood pressure during the study remained raised . Ischaemic heart disease and many cases of stroke are due to atherosclerotic arterial disease . This appears not to be favourably influenced by antihypertensive drug therapy
In primary prevention , the association of BP-lowering treatment with major cardiovascular events was dependent on baseline systolic BP ( SBP ) .
Conclusions and Relevance Primary preventive BP lowering is associated with reduced risk for death and CVD if baseline SBP is 140 mm Hg or higher .
At lower BP levels , treatment is not associated with any benefit in primary prevention but might offer additional protection in patients with CHD
Importance High blood pressure ( BP ) is the most important risk factor for death and cardiovascular disease ( CVD ) worldwide .
The optimal cutoff for treatment of high BP is debated .
Objective To assess the association between BP lowering treatment and death and CVD at different BP levels .