Hypertension (High BP) Risk II

In the previous sections, we listed the large uncertainties in these numbers (Margin of Error). As we explained in our statistics tutorial, one would need to have a major increase (e.g., by at least a factor of 10) in the number of people studied, in order to obtain a much smaller error. One way to achieve this goal, is to employ a "meta-study" - a study that combines data from many individual studies. The second reference was such a study, and the third was even broader, incorporating data equivalent to the tracking of 1.3 million people for 10 years! We now turn to this study - the last reference (ref 3).

The study totalled an exceptionally large population, involving 120,000 deaths among one million participants.

1) individual records were available for each of the participants in each study, allowing detailed analyses.
2) individuals with pre-existing vascular disease recorded were excluded, limiting any effects of disease on BP.
3) cause-specific mortality data, together with age at death, were generally available.
4) information on 286,000 repeat measurements made during prolonged follow-up allowed appropriate time-dependent correction for changes in their various categories during the study.

They have also performed a correction for changing BP that occurs during the study duration. This correction dramatically increases the dependence of the risk on BP. The reason is that if one only considers initial BP's at the start of the study, one defines groups that can subsequently mingle, blurring the distinction between them. Another way of saying this is that if you determine your risk at any age for a given BP, you need to adjust it as the BP changes with age. To some extent, the risk is enhanced because typically BP will rise with age, and consequently - the risk will rise with it.