Table 4. Primary and secondary outcomes at 90 days.
Values are numbers (percentages) unless stated otherwise.
| Outcomes | 30s Group (n = 673) | 60s Group (n = 611) | 90s Group (n = 595) | Control Group (n = 547) | Group difference P value# | Intervention/control difference P value## | |
|---|---|---|---|---|---|---|---|
| Continued (hot-to) cold shower after first 30 days* | 446 (66) | 378 (63) | 363 (62) | N.A. | 0.355 | N.A. | |
| Median (interquartile range) frequency of cold shower (times per week)* | 3 (0–7) | 3 (0–7) | 2 (0–6) | N.A. | 0.727 | N.A. | |
| Median (interquartile range) duration of cold shower (s)* | 30 (10–50) | 60 (40–80) | 60 (10–110) | N.A. | <0.001 | N.A. | |
| Will to continue (hot-to) cold shower after 90 days** | 546 (88) | 487 (84) | 490 (85) | N.A. | 0.199 | N.A. | |
| Median (interquartile range) SF-36 physical component score | 85.8 (78.9–90.4) | 86.4 (79.4–92) | 87.2 (79.8–92) | 86.4 (78.5–91.4) | 0.121 | 0.338 | |
| Median (interquartile range) SF-36 mental component score | 84.8 (76.7–89.6) | 84.4 (75.7–90.2) | 85.8 (78.0–90.6) | 84.4 (74.3–90) | 0.108 | 0.090 | |
| Median (interquartile range) work engagement score | 41 (33–46) | 42 (32–46) | 42 (32–46) | 41 (31.3–46) | 0.638 | 0.389 | |
| Median (interquartile range) anxiety score | 1 (0–3) | 1 (0–3) | 1 (0–3) | 1 (0–3) | 0.190 | 0.133 | |
| Reason of sickness absence if longer than 5 days*** | 0.326 | ||||||
| Influenza | 27 (64) | 17 (46) | 13 (42) | 20 (51) | |||
| Psychosocial (including burnout) | 6 (14) | 7 (19) | 6 (19) | 5 (13) | |||
| Musculoskeletal Injury | 4 (10) | 4 (11) | 2 (6) | 3 (8) | |||
| Bronchitis/pneumonia | 3 (7) | 0 (0) | 3 (10) | 2 (5) | |||
| Other upper respiratory tract infection (excluding influenza) | 2 (5) | 0 (0) | 2 (6) | 2 (5) | |||
| Other infection(s) | 0 (0) | 5 (14) | 1 (3) | 3 (8) | |||
| Other comorbidity (including operation) | 0 (0) | 4 (11) | 4 (13) | 4 (10) | |||
This study investigated the effect of cold showering on health and work: a trial randomizing a (hot-to-) cold shower for 30, 60, 90 seconds or a control group during 30 consecutive days followed by 60 days of showering cold at their own discretion for the intervention groups.
N.A. Not applicable
* Missing data in 2 participants in 30s Group, and 2 participants in 60s Group
** Missing data in 56, 30, and 20 participants (respectively)
*** Data collected in 42, 37, 31, and 39 participants (respectively)
# Difference between all groups (Kruskal Wallis)
## Difference between all interventional groups versus control group (Mann-Whitney U)