Abstract
Background: Recent declines in CVD mortality in Ireland
and other developed countries are partially attributable to favourable secular
trends in blood pressure (BP). However the underlying causes of these BP trends
are not well defined. In particular, the contribution of changes in the dietary
and other lifestyle determinants of population BP levels is unclear.
Objectives: To examine
changes in distribution and determinants of systolic blood pressure (SBP) in
middle-aged Irish adults over a 12 year period.
Methods: Data are
from two cross-sectional studies of men and women aged 47-73 years recruited from
17 General Practices in Cork and Kerry (N=1018, response rate 70%) and from one
large General Practice in Cork (N=2047,
response rate 67%) in 1998 and 2010 respectively. Similar procedures were used at
both time points, including recruitment methods, exclusion criteria, health and
lifestyle questionnaire, dietary assessment (food frequency questionnaire [FFQ])
and physical examination (height, weight and blood pressure). Dietary quality was
assessed using the Dietary Approaches to Stop Hypertension (DASH) score
constructed from the FFQ: higher scores indicating healthier diets. Changes in
mean SBP were examined in linear regression models and are presented as means (95%
C.I.).
Results:
Mean
SBP fell by 7.1 mmHG (138.0 to 130.9) in men and 4.7 mmHG (133.0 to 128.3) in
women between 1998 and 2010. Adjusted for age, gender and education mean SBP, was
5.8 mmHG (-7.3 to -4.5) lower in 2010 than in 1998. Average BMI increased from 27.8
(4.0) to 29.1 (4.1) in men and from 27.4 (4.6) to 28.0 (5.1) in women. By
contrast diet quality improved over the period in men and women from 22.5 (4.4)
to 27.6 (5.6) and from 23.5 (4.7) to 30.1 (5.6) respectively. Significant
trends in physical activity (favourable), smoking (favourable), and alcohol
intake (unfavourable) were observed. The proportion of the sample with doctor
diagnosed hypertension increased from 25% to 29% over the 12 year period. Adjusting
for age, gender, education, BMI, smoking and alcohol the change in mean SBP
remained relatively unchanged. Adjusting for DASH diet score the mean SBP
change it was reduced to 4.1 mmHG (-6.5 to -1.7) and on further adjustment for doctor
diagnosed hypertension it was reduced to 3.9 mmHG (-6.3 to -1.6).
Conclusions:
The
findings suggest that average blood pressure levels in the population are
falling, despite the increasing prevalence of obesity, and much of the change
is due to improvements in diet.