The relationship between blood pressure and mortality in the general population - it is not as simple as one might think - results from 20 years follow-up in the Study of Health in Pomerania

Hypertension is the leading risk-factor for cardiovascular disease (CVD). Whether treatment of hypertension below 140/90 mmHg or 120/80 mmHg is appropriate for optimal CVD risk reduction is unclear.

We used data from the population-based Study of Health in Pomerania (SHIP) to assess the relationship between baseline blood pressure and all-cause as well as cause-specific mortality in individuals with and without antihypertensive medication.

Participants were stratified by use of anti-hypertensive medication (w/ medication and w/o medication), and blood-pressure at baseline: (1) <120/80 mmHg, (2) <140/90 mmHg, and (3) hypertension ≥140/90mmHg. We used adjusted multivariable Cox regression models with a median follow up time up of 13.5 years (IQR: 9.4-20.8). Participants in group (1) w/o antihypertensive medication served as the reference group.

The following participants were included: w/o medication: (1) n=1,602; (2) n=1,766; (3) n=1,216; w/ medication: (1) n=278; (2) n=741; (3) n=951. Participants w/o and w/ antihypertensive medication had a mean age of 43 (SD 14) years and 60 (SD 12) years, respectively. A total of 52.4% (w/o medication) and 48.7% (w/ medication) were women. Overall 876 individuals died during follow-up. Individuals with medication at baseline always had a higher risk for all-cause mortality irrespective of measured blood pressure compared to the reference group: (1) HR 2.29 (95%-CI: 1.49-3.53); (2) HR 1.72 (95%-CI:1.19 -2.47); (3) HR 1.79 (95%-CI:1.26-2.55). Blood pressure in individuals without medication was not related to all-cause mortality. In subjects w/o medication, higher blood pressure levels were not significantly associated with CVD mortality. With intake of medication at the baseline examination, blood pressure <120/80 mmHg was not related to CVD mortality. On the other hand, blood pressure <140/90 mmHg (HR 2.74, 95%-CI: 1.02-7.39) and hypertension (HR 3.36, 95%-CI: 1.26-8.99) was significantly associated with higher CVD mortality in treated individuals. Participants w/o medication had no higher risk of non-CVD mortality compared to the reference group. In contrast, taking medication and a baseline blood pressure <120/80 mmHg was significantly related to a higher non-CVD mortality risk (HR 2.43, 95%-CI: 1.45-4.07), while <140/90 mmHg or hypertension w/ mediaction was not significantly related to higher risk of non-CVD mortality.

Normotensive blood pressure <120/80 mmHg in treated individuals was associated with lower risk of CVD-mortality. However, simultaneously this was also related with higher risk of non-CVD mortality. Thus, intensive antihypertensive treatment seems to shift the mortality risk from CVD to non-CVD without decreasing the risk for all-cause mortality.