Stroke, ischaemic heart disease and other vascular mortality: age-specific hazard ratios for given differences in usual blood pressure (source: Lewington et al., 2002)

The above figure, Figure 1: Stroke, ischaemic heart disease (IHD), and other vascular mortality: age-specific hazard ratios for given differences in usual blood pressure, is reproduced from Lewington S, Clarke R, Qizilbash N, Peto R, Collins R, Prospective Studies Collaboration. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet 2002; 360: 1903-13 with permission from Elsevier (see: Lewington et al., 2002)

Remarks

The data presented above were obtained from one million adults with no previous vascular disease in 61 prospective observational studies on blood pressure and mortality.The column “Number of deaths” refers to the number of death in the specified age groups in the study cohorts.

The hazard ratio can be interpreted as the relative risk for an event (in this case stroke, ischaemic heart disease, or other vascular disease) in persons whose systolic blood pressure is 20 mmHg lower (Figure A) or diastolic blood pressure is 10 mmHg lower (Figure B) compared with the reference person. A hazard ratio of 1 indicates no difference between both groups, a ratio <1 indicates a protective effect (reduced risk) and a ratio >1 indicates a hazardous effect (increased risk).

The authors sought to include all prospective observational studies that collected data on blood pressure, blood cholesterol, date of birth (or age), and sex at baseline, and in which cause of death and date of death (or age at death) for all participants during more than 5000 person years of follow-up were available.

Studies were identified through computer searches in MEDLINE and EMBASE, hand searches of meeting abstracts, and discussions with study investigators.

Studies that identified participants based on a positive history of stroke and ischaemic heart disease (IHD) were excluded. Participants with a history of stroke or IHD from the 61 contributing studies were also excluded.

In 58 out of the 61 studies blood pressure was measured. In three studies, blood pressure was self reported. In aggregate, these three studies and the remaining 58 studies gave similar results.

Blood pressure was measured variously across different studies using standard or random-zero sphygmomanometers. Similar results were found for studies with these two different methods. Blood pressure was typically measured in a sitting position.

Cause of death was assessed as detailed as possible according to the International Classification of Diseases (ICD) coding. In most studies, cause of death was recorded from death certificates. Information on stroke and CHD deaths was available for 99.8% of the participants’ follow-up (all but one study). Vascular causes of death other than stroke and CHD were available for 76% of the participants’ follow-up (all but seven studies)

For more detailed information see Lewington et al., 2002.