To the Editor:
A total of 7.8 million Americans participate in indoor tanning every year. Frequent indoor tanners may be more likely to participate in other potentially addictive behaviors as well. Indoor tanning participants have been found to consume more alcohol and to have higher rates of risky drinking.1–4 Frequent indoor tanning was associated with cigarette smoking among adolescent girls,5 but other studies have not found an association between indoor tanning and smoking1 or nicotine addiction.3 To more definitively investigate the association between indoor tanning and other potentially addictive behaviors, we performed a cross-sectional analysis using data from the Nurses’ Health Study II to evaluate whether frequent indoor tanning among young women is associated with smoking, alcohol intake, and caffeine consumption.
We performed age- and multivariable-adjusted logistic regression analyses to evaluate the associations of interest (Supplemental Methods; available via Mendeley at https://doi.org/10.17632/vdhbsndcmz.1). Indoor tanning frequency during high school, college, and at ages 25 to 35 years was reported in 2005. Smoking status, alcohol consumption, caffeine intake, and covariates were reported at baseline in 1989, when participants were aged 25 to 42 years, and in the 1991 follow-up questionnaire (Supplemental Fig 1; available via Mendeley at https://doi.org/10.17632/vdhbsndcmz.1).
Of 75,957 female nurses included in the analysis, 75.5% reported never indoor tanning. Women who indoor tanned more frequently tended to be younger and more physically active (Table I). In addition, women who indoor tanned more frequently reported more childhood sunburns and a higher mole count. Frequent indoor tanners were more likely to report a chronic disease, largely because of an increased percentage of participants with psoriasis who reported frequent indoor tanning (4.1% vs 2.4% of participants without psoriasis, P <.0001).
Table I.
Age-standardized baseline characteristics according to average indoor tanning during early life in the Nurses’ Health Study II*
| Indoor tanning, times per year | ||||
|---|---|---|---|---|
|
|
||||
| Characteristics | 0 (n = 57,241) | 1–2 (n = 10,900) | 3–11 (n = 5862) | 12+ (n = 1809) |
|
| ||||
| Age, y, mean (SD)† | 35.1 (4.5) | 33.3 (4.7) | 32.4 (4.7) | 31.7 (4.6) |
| Body mass index, kg/m2, mean (SD) | 24.1 (5.0) | 23.4 (4.5) | 23.5 (4.6) | 23.7 (4.7) |
| Physical activity, metabolic equivalents/week, mean (SD) | 23.2 (33.6) | 26.3 (37.5) | 28.5 (40.6) | 31.4 (44.2) |
| Red/blonde hair, % | 18.9 | 19.1 | 19.3 | 19.0 |
| ≥3 Blistering sunburns at age 15 to 20 y, % | 27 | 29.1 | 29.3 | 32.6 |
| Family history of melanoma, % | 4.4 | 4.9 | 4.6 | 4.9 |
| ≥3 Moles, % | 30.9 | 33 | 34.2 | 35.4 |
| Chronic disease,‡ % | 7.3 | 7.3 | 8.2 | 9.2 |
| Smoking | ||||
| Past, % | 21.3 | 25.0 | 25.4 | 23.6 |
| Current, % | 11.3 | 14.0 | 16.4 | 22.3 |
| Pack-years, mean (SD)§ | 11.3 (8.1) | 11.5 (8.8) | 11.3 (8.5) | 13.0 (9.3) |
| Duration, y, mean (SD)§ | 4.7 (7.6) | 5.7 (8.1) | 6.1 (8.2) | 7.1 (8.8) |
| ≥14 Alcoholic drinks/week | ||||
| Age 15–17 y, % | 0.4 | 0.4 | 0.4 | 0.9 |
| Age 18–22 y, % | 3.2 | 3.9 | 4.7 | 6.2 |
| Age 23–30 y, % | 2.0 | 2.3 | 2.9 | 4.3 |
| ≥3 Drinks on any day in a typical month during the past year, % | 27.4 | 36.6 | 39.3 | 42.1 |
| Alcohol intake, g/day, mean (SD) Caffeine | 3.0 (6.0) | 3.9 (6.9) | 3.8 (6.5) | 3.9 (7.1) |
| ≥6 cups of coffee/day, % | 2.1 | 2.1 | 2.6 | 4.5 |
| Caffeine, mg/day, mean (SD) | 233.4 (212.7) | 245.2 (214.5) | 255.4 (222.3) | 293.7 (250.1) |
SD, Standard deviation.
Values standardized to the age distribution of the study population.
Value is not age adjusted.
Chronic diseases include cancer, myocardial infarction, stroke, diabetes, hypertension, and common autoimmune diseases.
For past or current smokers.
Compared with participants who never tanned, frequent indoor tanners (≥12 times/year) were more than 2 times as likely to be current smokers at the study outset in 1989 (odds ratio [OR], 2.47; 95% confidence interval [CI], 2.18–2.80), to consume 14 or more alcoholic drinks per week at ages 23 to 30 years (OR, 2.21; 95% CI, 1.72–2.83), to have 3 or more alcoholic drinks on any day in a typical month (OR, 2.00; 95% CI, 1.81–2.20), or to drink 6 or more cups of coffee daily (OR, 2.21; 95% CI, 1.68–2.90) (Table II). These associations also showed a dose-response relationship that remained significant in our multivariable-adjusted analyses (P-trend < .0001). We also observed an association between frequency of indoor tanning and pack-years of smoking, smoking duration, daily alcohol consumption, and daily caffeine consumption (Supplemental Table I; available via Mendeley at https://doi.org/10.17632/vdhbsndcmz.1). Compared with those who never tanned, frequent users were more than 2 times as likely to participate in 1 other potentially addictive behavior (OR, 2.20; 95% CI, 1.97–2.45) and more than 3 times as likely to participate in 2 or more other potentially addictive behaviors (OR, 3.46; 95% CI, 2.95–4.06) (Supplemental Table II; available via Mendeley at https://doi.org/10.17632/vdhbsndcmz.1).
Table II.
Association between indoor tanning use in early life and smoking, alcohol consumption, and coffee intake*
| Times/y tanning | Age-adjusted OR (95% CI) | Multivariate† OR (95% CI) | Multivariate‡ OR (95% CI) |
|---|---|---|---|
|
| |||
| Past smoker* vs never smoker | |||
| Never | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| 1–2 | 1.29 (1.23–1.36) | 1.28 (1.22–1.35) | 1.26 (1.19–1.33) |
| 3–11 | 1.35 (1.26–1.44) | 1.33 (1.25–1.43) | 1.29 (1.20–1.40) |
| 12+ | 1.54 (1.37–1.73) | 1.51 (1.34–1.70) | 1.42 (1.24–1.63) |
| P-trend | <.0001 | <.0001 | <.0001 |
| Current smoker* vs never smoker | |||
| Never | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| 1–2 | 1.36 (1.27–1.44) | 1.36 (1.27–1.45) | 1.35 (1.26–1.45) |
| 3–11 | 1.71 (1.58–1.85) | 1.71 (1.58–1.85) | 1.59 (1.45–1.74) |
| 12+ | 2.42 (2.14–2.74) | 2.47 (2.18–2.80) | 2.32 (2.00–2.69) |
| P-trend | <.0001 | <.0001 | <.0001 |
| ≥14 drinks/week, 23–30 years old | |||
| Never | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| 1–2 | 1.15 (1.00–1.33) | 1.13 (0.98–1.31) | 1.08 (0.92–1.26) |
| 3–11 | 1.57 (1.32–1.86) | 1.50 (1.26–1.78) | 1.34 (1.10–1.62) |
| 12+ | 2.41 (1.89–3.08) | 2.21 (1.72–2.83) | 1.79 (1.35–2.38) |
| P-trend | <.0001 | <.0001 | <.0001 |
| ≥3 drinks/day | |||
| Never | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| 1–2 | 1.56 (1.49–1.63) | 1.52 (1.45–1.59) | 1.47 (1.40–1.55) |
| 3–11 | 1.75 (1.65–1.85) | 1.70 (1.60–1.80) | 1.62 (1.52–1.73) |
| 12+ | 2.09 (1.90–2.29) | 2.00 (1.81–2.20) | 1.82 (1.63–2.04) |
| P-trend | <.0001 | <.0001 | <.0001 |
| ≥6 cups coffee/day | |||
| Never | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| 1–2 | 0.95 (0.81–1.12) | 0.97 (0.83–1.14) | 0.83 (0.70–0.98) |
| 3–11 | 1.19 (0.98–1.46) | 1.20 (0.98–1.47) | 1.08 (0.87–1.33) |
| 12+ | 2.22 (1.69–2.92) | 2.21 (1.68–2.90) | 1.50 (1.11–2.04) |
| P-trend | <.0001 | <.0001 | .03 |
CI, Confidence interval; OR, odds ratio; Ref, reference.
Past and current smoking status, alcohol consumption, and coffee intake measured at study baseline in 1989.
Adjusted for age (continuous, years), BMI (continuous, kg/m2), physical activity (continuous, metabolic equivalents/week), hair color (red, blonde, light brown, dark brown, black), number of severe sunburns between ages 15 and 20 years (none, 1–2, 3–4, 5–9, 10+), mole count on lower legs (none, 1–2, 3–9, 10+), family history of melanoma ( yes/no), and chronic disease at baseline ( yes/no).
Past and current smoking was further adjusted for alcohol consumption (≥14 drinks per week at ages 15–17, 18–22, and 23–30 years; yes/no), coffee intake (≥6 cups per day, yes/no), and food addiction (yes/no). Alcohol consumption was further adjusted for smoking status (never, past, current), coffee intake, and food addiction. Coffee intake was further adjusted for alcohol consumption, smoking status, and food addiction.
Here, in a large, well-characterized cohort, we provide evidence that frequent indoor tanners were more likely to smoke, drink heavily, and consume more coffee around the time of reported tanning use. Indoor tanning may be a marker for women at risk of multiple addictions who can be targeted by public health strategies to prevent indoor tanning dependence and other addictions. Limitations of our study include retrospectively reported indoor tanning and limited generalizability to male and non-White populations.
Acknowledgments
We would like to thank the Nurses’ Health Study II participants for their dedication and commitment and the Channing Division of Network Medicine in Brigham and Women’s Hospital for their help.
Funding: Supported by a National Institutes of Health infrastructure grant (U01 CA176726 NHSII cohort). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Footnotes
IRB approval status: Reviewed and approved by the IRBs of the Brigham and Women’s Hospital and the Harvard T.H. Chan School of Public Health.
Reprints not available from the authors.
Conflicts of interest
None disclosed.
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