Table 2.
Summary of relative risks by sub-group analyses on indoor tanning and melanoma and non-melanoma skin cancer (NMSC).
| Ever Use of Indoor Tanning Device | Study N |
Summary RR (95% CI) |
Heterogeneity | |
|---|---|---|---|---|
| I2 (%) | P-Cochran | |||
| Non-melanoma skin cancer | ||||
| Histology | ||||
| Squamous cell carcinoma | 9 | 1.58 (1.38–1.81) | 27 | 0.21 |
| Basal cell carcinoma | 10 | 1.24 (1.00–1.55) | 61 | <0.01 |
| Anatomic site | ||||
| Not defined in each paper | 18 | 1.40 (1.18–1.65) | 77 | <0.01 |
| Type of indoor tanning | ||||
| NMSC, overall 1 | ||||
| Sunlamp | 4 | 1.22 (0.75–1.97) | 58 | 0.07 |
| Sunbed | 7 | 1.43 (1.10–1.85) | 82 | <0.01 |
| SCC | ||||
| Sunlamp | 2 | 1.72 (1.16–2.53) | 0 | 0.47 |
| Sunbed | 5 | 1.48 (1.20–1.83) | 61 | 0.04 |
| BCC | ||||
| Sunlamp | 2 | 1.21 (0.75–1.95) | 0 | 0.95 |
| Sunbed | 2 | 4.41 (1.10–77.08) | 83 | 0.02 |
| Study design | ||||
| Cohort 2 | 5 | 1.48 (1.18–1.84) | 83 | <0.01 |
| Case-control study (NMSC, overall) | 13 | 1.29 (0.97–1.72) | 70 | <0.01 |
| (SCC) | 5 | 1.76 (1.22–2.52) | 51 | 0.09 |
| (BCC) | 9 | 1.17 (0.84–1.64) | 65 | <0.01 |
| Publication year | ||||
| <2000 3 | 3 | 1.57 (0.75–3.27) | 50 | 0.13 |
| ≥2000 (NMSC, overall) | 15 | 1.39 (1.17–1.66) | 79 | <0.01 |
| (SCC) | 7 | 1.55 (1.25–1.92) | 73 | <0.01 |
| (BCC) | 8 | 1.19 (0.90–1.56) | 74 | <0.01 |
| Cutaneous melanoma | ||||
| Histology | ||||
| Superficial spreading melanoma (SSM) | 2 | 1.21 (0.81–1.82) | 75 | 0.05 |
| Nodular melanoma (NM) | 2 | 1.03 (0.51–2.11) | 66 | 0.09 |
| Lentigo maligna melanoma (LM) | 1 | 2.83 (1.37–5.84) | - | - |
| Others | 1 | 1.27 (0.63–2.58) | - | - |
| Anatomic site | ||||
| Trunk | 6 | 1.62 (1.25–2.10) | 57 | 0.04 |
| Head and neck | 5 | 1.16 (0.64–2.13) | 68 | 0.01 |
| Limbs | 5 | 1.38 (1.07–1.77) | 55 | 0.07 |
| Type of indoor tanning | ||||
| Sunlamp | 9 | 1.31 (1.04–1.64) | 52 | 0.03 |
| Sunbed | 19 | 1.17 (1.05–1.31) | 56 | <0.01 |
| Study design | ||||
| Cohort | 5 | 1.20 (1.11–1.29) | 7 | 0.37 |
| Case-control study | 31 | 1.30 (1.14–1.47) | 65 | <0.01 |
| Publication year | ||||
| <2000 | 15 | 1.28 (1.09–1.50) | 35 | 0.09 |
| ≥2000 | 21 | 1.26 (1.12–1.42) | 72 | <0.01 |
Abbreviation: P-Cochran, p-value in Cochran Q test; SCC, Squamous cell carcinoma; BCC, Basal cell carcinoma; NMSC, Non-melanoma skin cancer. 1 Three studies had the results of both SCC and BCC risks (Zhang et al. (2012); Bajdik et al. (1996); Han et al. (2006)). We calculated summary RRs for SCC risk and BCC risk, and the calculated summary RRs were included in the meta-analysis. 2 Four of five cohort studies were focused on SCC risk. 3 Two of three cohort studies were focused on SCC risk and two of three studies were focused on BCC risk.