Background
Methods
Study setting
Study design
Experimental study design | Alternative quasi-experimental study design | |
---|---|---|
Design | Cluster randomized controlled trial | Cluster nonrandomized single arm trial with calibration arm |
Blinding | No | No |
Pair-wise matching | Yes | No |
Sample size estimation (power calculation) | Assumptions: baseline mean 24-h urine sodium excretion of 180 mmol [16, 17, 42], standard deviation of 65, intra-cluster correlation coefficient of 0.05, 16 clusters and drop-out rate of 25%. Objective: detect between-group difference of at least 15% (i.e. 27 mmol) at trial end with alpha 0.05 and 80% power. | Assumptions: baseline mean 24-h urine sodium excretion of 180 mmol [16, 17, 42], standard deviation of 65, intra-cluster correlation coefficient of 0.05, and drop-out rate of 10%. Objective: detect sodium intake reduction by 15% (i.e. 27 mmol) until trial end with alpha 0.05 and 80% power. |
Numbers required to measure effectiveness | Number of clusters (participants, before 25% drop-out) 8 intervention clusters (N = 395, 50 per cluster) 8 control clusters (N = 395, 50 per cluster) | Number of clusters (participants, before 10% drop-out) 7 intervention clusters (N = 112, 16+ per cluster) |
Recruitment
Eligibility criteria, registration and consent
Cluster level
Participant level
Study objectives
Primary outcome measure
Secondary outcome measures
Intervention design
Environmental intervention, theoretical background and program
Educational intervention, theoretical background and program
Data collection at cluster level
Catering survey
Intervention actions and food sampling
Laboratory analysis of sodium and potassium concentrations in food
Estimation of sodium and potassium content of menu components and servings
Data collection at participant level
Health questionnaire
Health assessments
Sodium, potassium, and iodine intake measurements
Food record checklist
24-h urine collection
Spot urine collection
Laboratory determination of urinary sodium, potassium, creatinine, and iodine concentrations
Estimation of daily sodium, potassium, and iodine excretion/intake
Completeness of 24-h urine samples
Blood pressure
Anthropometrics
Data management
Statistical analysis
Dissemination
Baseline information
Participation
Cluster level
Participant level
Baseline characteristics
Cluster level
All | Intervention group | Control group | ||
---|---|---|---|---|
Number organizations | N | 8 | 7 | 1 |
Manufacturing and service industry | n | 2 | 2 | – |
Administration and offices | n | 2 | 1 | 1 |
University and research institutions | n | 2 | 2 | – |
Social service and welfare institutions | n | 2 | 2 | – |
Health promotion is part of corporate philosophy | n | 6 | 6 | 0 |
Total number employees eligible to participate | N | 5794 | 5394 | 400 |
Median number employees eligible to participate | Median (range) | 684 (228–1380) | 868 (228–1380) | 400a |
% Women | Median (range) | 48.5% (19% – 70%) | 56% (19% - 70%) | 37% |
% Men | Median (range) | 51.5% (30% – 81%) | 44% (30% - 81%) | 63% |
Kind of catering facility | ||||
Corporate entity | n | 2 | 2 | 0 |
Outsourced | n | 6 | 5 | 1 |
Number luncheons sold per day overall (incl. buffet) | Median (range) | 214.5 (128–636) | 232 (128–636) | 161 |
% Plated menus (all kind) | Median (range) | 83.9% (76.1% - 91.8%) | 85% (76.1% - 93.9%) | 76.4% |
% Self-service buffet | Median (range) | 16.1% (8.2% - 23.9%) | 15% (6.1% - 23.9%) | 23.6% |
Size of catering facility (sales numbers) | ||||
Small (< 150 luncheons/day) | n | 2 | 2 | 0 |
Medium (150–500 luncheons/day) | n | 5 | 4 | 1 |
Large (> 500 luncheons/day) | n | 1 | 1 | 0 |
Catering system (multiple answers) | ||||
cook-serve | n | 7 | 6 | 1 |
cook-hot hold | n | 7 | 7 | 0 |
cook-chill | n | 6 | 6 | 0 |
cook-freeze | n | 1 | 1 | 0 |
Processing/convenience level of foods/products (two answers/most frequent per organization) | ||||
level 0 (unprocessed foods) | n | 4 | 4 | 0 |
level 1 (ready-for-kitchen) | n | 5 | 4 | 1 |
level 2 (ready-to-cook) | n | 4 | 4 | 0 |
level 3 (ready-to-end-cook) | n | 1 | 0 | 1 |
level 4 (ready-to-heat) | n | 2 | 2 | 0 |
level 5 (ready-to-eat) | n | 0 | 0 | 0 |
Number catering staff | N | 139 | 131 | 8 |
Qualified | n | 84 | 79 | 5 |
Unqualified | n | 55 | 52 | 3 |
Catering staff knows | N | 60 | 54 | 6 |
Swiss quality standards for health-promoting communal catering | n | 40 | 35 | 5 |
Recommended salt intake (< 5 g/day) | n | 26 | 23 | 3 |
Participant level
All | Intervention group | Control group | ||
---|---|---|---|---|
Number participants | N | 141 | 128 | 13 |
Women | n (%) | 70 (49.6%) | 65 (50.8%) | 5 (38.5%) |
Men | n (%) | 71 (50.4%) | 63 (49.2%) | 8 (61.5%) |
Age (years) | Median (range) | 46 (21–61) | 46 (21–61) | 48 (30–59) |
Mean (95% CI) | 44.6 (42.8, 46.4) | 44.1 (42.2, 46) | 49.3 (44.6, 54) | |
15–34 | n (%) | 32 (22.7%) | 31 (24.2%) | 1 (7.7%) |
35–44 | n (%) | 24 (17.0%) | 23 (18.0%) | 1 (7.7%) |
45–54 | n (%) | 53 (37.6%) | 45 (35.2%) | 8 (61.5%) |
55–65 | n (%) | 32 (22.7%) | 29 (22.7%) | 3 (23.1%) |
Nationality | ||||
Swiss | n (%) | 119 (84.4%) | 107 (83.6%) | 12 (92.3%) |
Non-Swiss | n (%) | 22 (15.6%) | 21 (16.4%) | 1 (7.7%) |
Household size | Median (range) | 3 (1–6) | 3 (1–6) | 3 (1–6) |
Mean (95% CI) | 2.6 (2.4, 2.8) | 2.5 (2.4, 2.7) | 2.8 (2, 3.7) | |
Household type (or structure) | ||||
Single | n (%) | 23 (16.3%) | 21 (16.4%) | 2 (15.4%) |
Single or couple with children | n (%) | 65 (46.1%) | 58 (45.3%) | 7 (53.8%) |
Two or more adults no children | n (%) | 53 (37.6%) | 49 (38.3%) | 4 (30.8%) |
Education | ||||
Primary/obligatory | n (%) | 2 (1.4%) | 2 (1.6%) | 0 (0.0%) |
Secondary | n (%) | 35 (24.8%) | 34 (26.6%) | 1 (7.7%) |
Tertiary | n (%) | 104 (73.8%) | 92 (71.9%) | 12 (92.3%) |
Working position | ||||
Trainee | n (%) | 3 (2.1%) | 3 (2.3%) | 0 (0.0%) |
White and blue collar workers | n (%) | 61 (43.3%) | 52 (40.6%) | 9 (69.2%) |
Lower and middle management | n (%) | 67 (47.5%) | 63 (49.2%) | 4 (30.8%) |
Top management | n (%) | 10 (7.1%) | 10 (7.8%) | 0 (0.0%) |
Worktime equivalent (% Full Time Equivalent FTE) | Median (range) | 100 (40–100) | 100 (40–100) | 90 (60–100) |
Mean (95% CI) | 90.4 (88.1, 92.7) | 90.8 (88.4, 93.3) | 86.5 (78.8, 94.3) | |
Eating lunch at staff restaurant (times/week) | ||||
0–1 times/week | n (%) | 30 (21.3%) | 30 (23.4%) | 0 (0.0%) |
2–3 times/week | n (%) | 70 (49.6%) | 64 (50.0%) | 6 (46.2%) |
4–7 times/week | n (%) | 41 (29.1%) | 34 (26.6%) | 7 (53.8%) |