Summary of findings 1. Summary of findings table 'dryness symptoms'.
| Indoor air humidification compared with no indoor air humidification for prevention or reducing dryness symptoms of the eyes, skin and nose (URT) | ||||||
| Population: Adults Setting: Occupational Intervention: Indoor air humidification Comparison: No indoor air humidification | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | No of participants (studies)# | Quality of the evidence (GRADE) | Comments | |
| Risk with no humidification | Risk with humidification | |||||
|
Dry eye Cross‐over study (cluster‐RCT) after 6 weeks |
Study population | OR 0.54 (0.37 to 0.79) | 211 (1 cross‐over cluster‐RCT) | ⊕⊕⊝⊝ LOWa | The cluster‐randomised cross‐over study reported a significant reduction in eye dryness following indoor air humidification over a study period of 6 weeks | |
| 359 per 1000 | 232 per 1000 (172 to 307) | |||||
|
Dry eye Cross‐over studies (cluster non‐RCT) after 6 – 12 weeks |
Study population | OR 0.58 (0.27 to 1.25) | 407 (2 cross‐over cluster non‐RCTs) | ⊕⊕⊝⊝ LOW | 2 cluster non‐randomised cross‐over studies reported non‐significant positive effects on eye dryness following indoor air humidification over a study period of 1 ‐ 3 months | |
| 359 per 1000 | 245 per 1000 (131 to 412) | |||||
|
Dry eye Before‐and‐after studies after 6 weeks ‐ 4 months |
Study population | OR 0.57 (0.23 to 1.41) | 102 (2 before‐and‐after studies) | ⊕⊝⊝⊝ VERY LOWb, c | 2 before‐and‐after studies showed non‐significant positive effect of indoor air humidification on dry eye symptoms over a study period of 6 weeks to 4 months | |
| 359 per 1000 | 242 per 1000 (114 to 441) | |||||
|
Dry skin Cross‐over studies (cluster non‐RCT) after 6 ‐ 12 weeks |
Study population | OR 0.66 (0.33 to 1.32) | 407 (2 non‐RCT) | ⊕⊕⊝⊝ LOW | Both cluster non‐randomised cross‐over studies showed an alleviation of skin dryness following indoor air humidification over a study period of 1 ‐ 3 months | |
| 380 per 1'000 | 288 per 1000 (168 to 447) | |||||
|
Dry skin Before‐and‐after Studies after 12 weeks to 4 months |
Study population | OR 0.69 (0.33 to 1.47) | 121 (2 before‐and‐after studies) | ⊕⊝⊝⊝ VERY LOWd | 1 before‐and‐after study yielded a positive effect of indoor air humidification on skin dryness over a study period of 12 weeks. 1 before‐and‐after study showed no effect following indoor air humidification over a study period of 4 months |
|
| 380 per 1000 | 297 per 1000 (168 to 474) | |||||
|
Dry nose (dry upper respiratory tract) Cross‐over study (cluster non‐RCT) after 6 weeks |
Study population | OR 0.87 (0.53 to 1.42) | 368 (1 non‐RCT) |
⊕⊕⊝⊝ LOW | The cluster non‐randomised cross‐over study reported an alleviation of nose dryness following indoor air humidification over a study period of 6 weeks. Hence, the result was not statistically significant | |
| 246 per 1000 | 221 per 1000 (147 to 317) | |||||
|
Dry nose (dry upper respiratory tract) Cross‐over study (cluster‐RCT) after 6 weeks |
Study population | OR 1.08 (0.73 to 1.60) | 211 (1 RCT) | ⊕⊕⊝⊝ LOWd | The cluster‐randomised cross‐over study revealed no effect of indoor air humidification on nose dryness over a study period of 6 weeks | |
| 246 per 1000 | 259 per 1000 (194 to 337) | |||||
| No studies were identified for URT (Upper respiratory infections) | ||||||
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). #Number of participants included in the analysis were reported, See Characteristics of included studies for number of recruited and included participants. CI: Confidence interval; OR: Odds ratio; RCT: randomised controlled trial | ||||||
| GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. | ||||||
aDowngraded twice due to high risk of bias: there were missing outcome data (the reason was not stated); the items: randomisation, allocation concealment, blinding unclear, selective outcome reporting were unclear. bDowngraded twice due to high risk of bias: in one study the percentage of withdrawals and dropouts exceeds 20% for short‐term follow‐up and the results are presented for a dynamic population. cDowngraded once due to imprecision: small sample sizes. dDowngraded once due to high risk of bias: lack of control for confounding and other source of bias (dynamic population).
We did not upgrade any of the individual studies.