Background
Methods
Ethics
Study area and population
Household survey and population census
Recruitment of participants
Baseline assessment
Randomisation and power calculations
Unit change | Systolic B.P. (mmHg) | Diastolic B.P. (mmHg) |
---|---|---|
50 mmol of 24 h urinary sodium | 2.17 (0.44 to 3.91)#
| 1.01 (0.08 to 1.94)#
|
Unit of sodium: creatinine ratio | 0.45 (0.17 to 0.75)#
| 0.18 (0.02 to 0.33)#
|
Unit of sodium: potassium ratio | 1.74 (0.45 to 3.03)#
| 1.16 (0.43 to 1.80)#
|
Intervention programme
Follow-up
Statistical analysis
Results
General characteristics
Effect of time of day
Relationship between urinary sodium and BP
Effect of the intervention programme on salt intake
Intervention (n = 522) | Control (n = 491) | |
---|---|---|
Age | 54 (11) | 55 (11) |
Female n (%) | 324 (62) | 304 (62) |
Height in cm | 160 (8) | 161 (8) |
Weight in kg | 54 (11) | 54 (11) |
Body mass index (kg/m2) | 21 (4) | 21 (4) |
Systolic blood pressure (mmHg)¶
| 129 (25) | 127 (27) |
Diastolic blood pressure (mm Hg)¶
| 77 (13) | 76 (13) |
Heart rate (bpm)¶
| 74 (12) | 72 (12) |
Urinary sodium (mmol/24 h) | 99.9 (44.7) | 102.5 (45.3) |
Urinary potassium (mmol/24 h) | 47.5 (23.2) | 49.3 (23.6) |
Urinary creatinine (mmol/24 h) | 8.4 (2.6) | 8.4 (2.6) |
Urinary sodium/potassium ratio | 2.4 (1.2) | 2.4 (1.3) |
Urinary sodium/creatinine ratio | 12.4 (5.3) | 12.7 (5.6) |
Urinary potassium/creatinine ratio | 5.9 (2.8) | 6.1 (2.8) |
Current smoking n (%) | 31 (6) | 41 (8) |
Alcohol drinking n (%) | 199 (38) | 211 (43) |
Hypertensive n (%) | 154 (30) | 137 (28) |
(a) | Baseline | Three months | ||
---|---|---|---|---|
Intervention (n = 444) | Control (n = 450) | Intervention (n = 444) | Control (n = 450) | |
Systolic blood pressure (mm Hg) | 128.5 (24.7) | 127.3 (26.3) | 124.6 (26.6) | 123.8 (26.0) |
Diastolic blood pressure (mm Hg) | 76.8 (13.0) | 75.8 (13.5) | 74.2 (13.7) | 74.0 (14.1) |
Urinary sodium (mm/24 h) | 100.9 (44.3) | 103.6 (45.3) | 94.0 (44.5) | 97.5 (42.3) |
Urinary potassium (mm/24 h) | 48.3 (23.5) | 49.3 (23.4) | 50.1 (20.8) | 52.1 (23.6) |
Urinary creatinine (mm/24 h) | 8.4 (2.6) | 8.4 (2.6) | 7.8 (2.5) | 7.9 (2.8) |
Urinary sodium/potassium ratio | 2.4 (1.2) | 2.4 (1.3) | 2.1 (1.1) | 2.1 (1.1) |
Urinary sodium/creatinine ratio | 12.4 (5.2) | 12.8 (5.6) | 12.4 (5.4) | 13.0 (5.6) |
Urinary potassium/creatinine ratio | 6.0 (2.8) | 6.1 (2.8) | 6.7 (2.9) | 6.9 (2.9) |
(b) | Baseline | Six months | ||
Intervention (n = 399) | Control (n = 402) | Intervention (n = 399) | Control (n = 402) | |
Systolic blood pressure (mm Hg) | 129.2 (24.6) | 125.6 (25.5) | 127.9 (27.7) | 127.4 (26.0) |
Diastolic blood pressure (mm Hg) | 76.9 (13.0) | 75.2 (13.3) | 76.0 (14.2) | 78.7 (14.3) |
Urinary sodium (mm/24 h) | 100.7 (45.2) | 104.2 (45.5) | 91.8 (41.8) | 89.8 (39.1) |
Urinary potassium (mm/24 h) | 48.5 (23.9) | 50.9 (24.2) | 48.2 (21.5) | 52.1 (21.9) |
Urinary creatinine (mm/24 h) | 8.4 (2.6) | 8.4 (2.5) | 8.0 (2.6) | 8.0 (2.5) |
Urinary sodium/potassium ratio | 2.4 (1.3) | 2.4 (1.3) | 2.2 (1.2) | 1.9 (1.0) |
Urinary sodium/creatinine ratio | 12.4 (5.2) | 12.8 (5.6) | 11.9 (5.1) | 11.7 (4.7) |
Urinary potassium/creatinine ratio | 6.0 (2.9) | 6.3 (2.9) | 6.3 (2.7) | 6.8 (2.7) |
Variable | 3 months (n = 894) | 6 months (n = 801) |
---|---|---|
SBP (mmHg) | -0.48 (-5.45 to 4.50) | -2.54 (-6.54 to 1.45) |
DBP (mmHg) | -1.02 (-3.95 to 1.91) | -3.95 (-7.11 to -0.78)** |
Urinary sodium (mmol/24 h) | -0.5 (-12.3 to 11.3) | 6.0 (-4.1 to 16.1) |
Urinary sodium: creatinine | -0.01 (-1.35 to 1.32) | 0.85 (-0.53 to 2.24) |
Urinary sodium: potassium | 0.08 (-0.22 to 0.39) | 0.30 (0.02 to 0.57)* |
Effect of the intervention programme on BP
Intention-to-treat analysis
On-diet analysis
Unit change | Month | Systolic B.P. (mmHg) | Diastolic B.P. (mmHg) |
---|---|---|---|
50 mmol of 24 h urinary sodium | 3 | 2.12 (1.03 to 3.21)#
| 1.11 (0.45 to 1.78)#
|
6 | 1.34 (0.08 to 2.60)* | 0.30 (-0.45 to 1.04) | |
Unit of sodium: creatinine ratio | 3 | 0.33 (0.15 to 0.51)#
| 0.14 (0.03 to 0.25)** |
6 | 0.30 (0.08 to 0.53)§
| 0.03 (-0.10 to 0.17) | |
Unit of sodium: potassium ratio | 3 | 1.59 (0.73 to 2.46)#
| 0.48 (-0.05 to 1.00) |
6 | 1.94 (0.97 to 2.90)#
| 0.47 (-0.11 to 1.04) |