Night shift work, chemical coexposures and risk of female breast cancer in the Norwegian Offshore Petroleum Workers (NOPW) cohort: a prospectively recruited case-cohort study.

OBJECTIVES: This study examined the association between night shift work and risk of breast cancer, overall and by hormone receptor subtype, among females in the Norwegian Offshore Petroleum Workers (NOPW) cohort. We also examined the association of coexposure (chlorinated degreasers and benzene) and breast cancer risk, and possible interaction with work schedule. DESIGN: Prospectively recruited case-cohort study within the NOPW cohort. SETTING: Female offshore petroleum workers active on the Norwegian continental shelf. PARTICIPANTS: 600 female workers (86 cases and 514 non-cases) were included in the study. We excluded workers that died or emigrated before start of follow-up, had missing work history, were diagnosed with breast cancer or other prior malignancy (except non-melanoma skin cancer) before start of follow-up. RESULTS: No overall association was found between breast cancer risk and work schedule (HR 0.87, 95% CI 0.52 to 1.46 for work schedule involving night shift vs day shift only). There was no significant association between work schedule and risk of any breast cancer subtype. No significant interactions were found between work schedule and chemical coexposures (breast cancer overall Pinteraction chlorinated degreasers=0.725 and Pinteraction benzene=0.175). CONCLUSIONS: Our results did not provide supporting evidence that work schedule involving night shift affects breast cancer risk in female offshore petroleum workers, but should be considered cautiously due to few cases. Further studies with larger sample sizes are warranted.

Detection of gluten immunogenic peptides and the Celiac Disease Adherence Test to monitor gluten-free diet: a pilot study.

Gluten immunogenic peptides (GIP) in feces and/or urine have recently been proposed as a sensitive and specific marker to detect ongoing gluten intake. Here, we compared GIP with the Celiac Disease Adherence Test (CDAT), a simple validated self-administered questionnaire that measures adherence to gluten-free diet (GFD). Of 70 subjects (59 women), six were classified as non-adherent by fecal GIP (mean 0.23 µg/g, standard deviation 0.08, range 0.082-0.319), including five classified as non-adherent by CDAT. GFD adherence was significantly higher by GIP than CDAT (p < 0.001). Fecal GIP may be useful as a biomarker for ongoing gluten intake that is not possible to detect with current clinical methods to assess GFD adherence, and may play a role in the management of persistent gastrointestinal symptoms in celiac disease.

Use of Immunomodulating Drugs and Risk of Cutaneous Melanoma: A Nationwide Nested Case-Control Study.

PURPOSE: Cutaneous melanoma is among the fastest growing malignancies in Norway and ultraviolet radiation (UVR) exposure is the primary environmental risk factor. Immunomodulating drugs can increase skin photosensitivity and suppress immune responses, and by such mechanisms influence melanoma risk. We, therefore, aimed to examine the associations between use of immunomodulating drugs and melanoma risk, at a nationwide population level. PATIENTS AND METHODS: In the Cancer Registry of Norway, we identified all cases aged 18-85 with a first primary cutaneous melanoma diagnosed in 2007-2015 (n=12,106). These were matched to population controls from the Norwegian National Registry 1:10 (n=118,564), on sex and year of birth using risk set sampling. Information on prescribed drugs (2004-2015) was obtained by linkage to the Norwegian Prescription Database (NorPD). Conditional logistic regression was used to estimate rate ratios (RRs) and 95% confidence intervals (CIs) for associations between use of immunomodulating drugs (immunosuppressants and corticosteroids) and melanoma risk, adjusted for ambient UVR and other drug use. RESULTS: Compared with ≤1 prescription, use of ≥8 prescriptions of immunosuppressants was associated with increased risk of melanoma (RR 1.50, 95% CI 1.27, 1.77). Similar associations were found for subgroups of immunosuppressants: drugs typically prescribed to organ transplant recipients (OTRs) (RR 2.02, 95% CI 1.35, 3.03) and methotrexate (RR 1.27, 95% CI 1.04, 1.55). Similar results were found for high levels of cumulative doses and across all histological subtypes. Use of corticosteroids was not associated with melanoma risk. CONCLUSION: We found a positive association between use of immunosuppressants and melanoma risk, with the highest risk seen for drugs prescribed to OTRs. Knowledge about this risk increase is important for physicians and users of these drugs, for intensified surveillance, awareness and cautious sun exposure.

Cardiovascular, antidepressant and immunosuppressive drug use in relation to risk of cutaneous melanoma: a protocol for a prospective case-control study.

INTRODUCTION: The incidence of cutaneous melanoma (hereafter melanoma) has increased dramatically among fair-skinned populations worldwide. In Norway, melanoma is the most rapidly growing type of cancer, with a 47% increase among women and 57% among men in 2000-2016. Intermittent ultraviolet exposure early in life and phenotypic characteristics like a fair complexion, freckles and nevi are established risk factors, yet the aetiology of melanoma is multifactorial. Certain prescription drugs may have carcinogenic side effects on the risk of melanoma. Some cardiovascular, antidepressant and immunosuppressive drugs can influence certain biological processes that modulate photosensitivity and immunoregulation. We aim to study whether these drugs are related to melanoma risk. METHODS AND ANALYSIS: A population-based matched case-control study will be conducted using nation-wide registry data. Cases will consist of all first primary, histologically verified melanoma cases diagnosed between 2007 and 2015 identified in the Cancer Registry of Norway (14 000 cases). Ten melanoma-free controls per case (on date of case melanoma diagnosis) will be matched based on sex and year of birth from the National Registry of Norway. For the period 2004-2015, and by using the unique personal identification numbers assigned to all Norwegian citizens, the case-control data set will be linked to the Norwegian Prescription Database for information on drugs dispensed prior to the melanoma diagnosis, and to the Medical Birth Registry of Norway for data regarding the number of child births. Conditional logistic regression will be used to estimate associations between drug use and melanoma risk, taking potential confounding factors into account. ETHICS AND DISSEMINATION: The project is approved by the Regional Committee for Medical Research Ethics in Norway and by the Norwegian Data Protection Authority. The study is funded by the Southeastern Norway Regional Health Authority. Results will be published in peer-reviewed journals and disseminated further through scientific conferences, news media and relevant patient interest groups.

The Norwegian dietary guidelines and colorectal cancer survival (CRC-NORDIET) study: a food-based multicentre randomized controlled trial.

BACKGROUND: Colorectal cancer survivors are not only at risk for recurrent disease but also at increased risk of comorbidities such as other cancers, cardiovascular disease, diabetes, hypertension and functional decline. In this trial, we aim at investigating whether a diet in accordance with the Norwegian food-based dietary guidelines and focusing at dampening inflammation and oxidative stress will improve long-term disease outcomes and survival in colorectal cancer patients. METHODS/DESIGN: This paper presents the study protocol of the Norwegian Dietary Guidelines and Colorectal Cancer Survival study. Men and women aged 50-80 years diagnosed with primary invasive colorectal cancer (Stage I-III) are invited to this randomized controlled, parallel two-arm trial 2-9 months after curative surgery. The intervention group (n = 250) receives an intensive dietary intervention lasting for 12 months and a subsequent maintenance intervention for 14 years. The control group (n = 250) receives no dietary intervention other than standard clinical care. Both groups are offered equal general advice of physical activity. Patients are followed-up at 6 months and 1, 3, 5, 7, 10 and 15 years after baseline. The study center is located at the Department of Nutrition, University of Oslo, and patients are recruited from two hospitals within the South-Eastern Norway Regional Health Authority. Primary outcomes are disease-free survival and overall survival. Secondary outcomes are time to recurrence, cardiovascular disease-free survival, compliance to the dietary recommendations and the effects of the intervention on new comorbidities, intermediate biomarkers, nutrition status, physical activity, physical function and quality of life. DISCUSSION: The current study is designed to gain a better understanding of the role of a healthy diet aimed at dampening inflammation and oxidative stress on long-term disease outcomes and survival in colorectal cancer patients. Since previous research on the role of diet for colorectal cancer survivors is limited, the study may be of great importance for this cancer population. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01570010 .

Cutaneous head and neck melanoma (CHNM): A population-based study of the prognostic impact of tumor location.

BACKGROUND: Most studies of cutaneous head and neck melanomas (CHNM) have reported poorer survival in CHNM compared with other sites, especially on the scalp/neck. OBJECTIVE: We sought to compare patient and tumor characteristics between CHNM and cutaneous trunk and extremity melanomas and between CHNM locations (face/ear vs scalp/neck, anterior vs posterior), and to study prognostic factors in patients with CHNM. METHODS: We studied all CHNM (n = 1074) from 8120 cases of cutaneous melanomas diagnosed in Norway in 2008 to 2012. RESULTS: Compared with cutaneous trunk and extremity melanomas, CHNM were more frequently found in men, more often nodular and lentigo maligna cutaneous melanomas, and diagnosed at higher T stage (P ≤ .01). CHNM located on posterior sites were diagnosed at significantly higher T stage, and were significantly more often diagnosed with ulceration and at more advanced stage compared with CHNM located on anterior sites (P < .001). T stage and clinical stage were the only significant prognostic factors for melanoma-specific and overall death in the multivariable analysis (P < .001). LIMITATIONS: Low number of cases and the relatively high frequency of missing values are limitations. CONCLUSION: More advanced CHNM were diagnosed on posterior compared with anterior locations, but location was not a significant prognostic factor for cutaneous melanoma-specific or overall death in the multivariable models.

Increased levels of phthalates in very low birth weight infants with septicemia and bronchopulmonary dysplasia.

Very low birth weight infants (VLBW; birth weight<1500g) are exposed to potentially harmful phthalates from medical devices during their hospital stay. We measured urinary phthalate concentrations among hospitalized VLBW infants participating in a nutritional study. Possible associations between different phthalates and birth weight (BW), septicemia and bronchopulmonary dysplasia (BPD) were evaluated. Forty-six VLBW infants were enrolled in this randomized controlled nutritional study. The intervention group (n=24) received increased quantities of energy, protein, fat, essential fatty acids and vitamin A, as compared to the control group (n=22). The concentrations of 12 urinary phthalate metabolites were measured, using high-performance liquid chromatography coupled to tandem mass spectrometry, at 3 time points during the first 5weeks of life. During this study, the levels of di (2-ethylhexyl) phthalate (DEHP) metabolites decreased, whereas an increasing trend was seen regarding metabolites of di-iso-nonyl phthalate (DiNP). Significantly higher levels of phthalate metabolites were seen in infants with lower BW and those diagnosed with late onset septicemia or BPD. A significant positive correlation between the duration of respiratory support and DEHP metabolites was observed (p≤0.01) at 2.9weeks of age. Birth weight was negatively associated with urinary phthalate metabolite concentrations. Infants with lower BW and those diagnosed with septicemia or BPD experienced prolonged exposure from medical equipment containing phthalates, with subsequent higher levels of phthalate metabolites detected. Clinical Trial Registration no.: NCT01103219.

Food items contributing most to variation in antioxidant intake; a cross-sectional study among Norwegian women.

BACKGROUND: Fruit and vegetable intake has been found to reduce the risk of cardiovascular disease, certain types of cancer and diabetes mellitus. It is possible that antioxidants play a large part in this protective effect. However, which foods account for the variation in antioxidant intake in a population is not very clear. We used food frequency data from a population-based sample of women to identify the food items that contributed most to the variation in antioxidant intake in Norwegian diet. METHODS: We used data from a study conducted among participants in the Norwegian Breast Cancer Screening Program (NBCSP), the national program which invites women aged 50-69 years to mammographic screening every 2 years. A subset of 6514 women who attended the screening in 2006/2007 completed a food frequency questionnaire (FFQ). Daily intake of energy, nutrients and antioxidant intake were estimated. We used multiple linear regression analysis to capture the variation in antioxidant intake. RESULTS: The mean (SD) antioxidant intake was 23.0 (8.5) mmol/day. Coffee consumption explained 54% of the variation in antioxidant intake, while fruits and vegetables explained 22%. The twenty food items that contributed most to the total variation in antioxidant intake explained 98% of the variation in intake. These included different types of coffee, tea, red wine, blueberries, walnuts, oranges, cinnamon and broccoli. CONCLUSIONS: In this study we identified a list of food items which capture the variation in antioxidant intake among these women. The major contributors to dietary total antioxidant intake were coffee, tea, red wine, blueberries, walnuts, oranges, cinnamon and broccoli. These items should be assessed in as much detail as possible in studies that wish to capture the variation in antioxidant intake.

Ultraviolet exposure and mortality among women in Sweden.

BACKGROUND: Ecological studies have reported possible effects of sunlight on the risk of several diseases. Little evidence is available on the association between mortality and solar and artificial UV exposure by individual level from prospective studies. METHODS: The Swedish Women's Lifestyle and Health cohort study included women aged 30 to 49 years in 1991-1992. Participants completed a questionnaire and were followed-up through linkages to national registries until the end of 2006. Cox models were used to estimate adjusted HRs and 95% CIs for all-cause mortality and for cancer and cardiovascular disease (CVD) mortality. RESULTS: During 15 years of follow-up, among the 38,472 women included in the present study, 754 deaths occurred: 457 due to cancer and 100 due to CVD. When combining the information on sun exposure from age 10 to 39 years, women who got sunburned twice or more per year during adolescence had a reduced all-cause mortality, compared with women who had been sunburned once or less. A reduced risk for all-cause and CVD mortality was observed in women who went on sunbathing vacations more than once a year over three decades. Solarium use once or more per month for at least one decade increased the risk of all-cause mortality, when compared with women who never used a solarium. CONCLUSIONS: Solar UV exposure was associated with reduced overall and CVD mortality, whereas artificial UV exposure was associated with increased overall and cancer mortality among Swedish women. IMPACT: Moderate sun exposure may protect against cause-specific mortality.

Cancer risk in Norwegian world class athletes.

BACKGROUND: Physical activity appears to be inversely related to cancer risk, although the evidence is convincing for colon cancer only. As physical activity levels are difficult to measure in the general population, we aimed to investigate how physical activity influences cancer risk using a cohort of Norwegian world class athletes. METHODS: The cohort includes 3,428 athletes. Individual questionnaires gave information about physical activity and lifestyle variables until attained age. To elucidate the level of cancer risk, groups of athletes were compared to the general population (external comparisons) and to each other (internal comparisons). RESULTS: A slightly reduced risk of total cancer was observed in the cohort of athletes, but stronger effects were observed for subgroups. The risk reduction was most pronounced for lung cancer and for leukemia/lymphoma. In women, a threefold increased risk of thyroid cancer was observed. CONCLUSION: This cohort of athletes seems to have a reduced risk of cancer. The beneficial association, however, is weak and may be attributed to healthy lifestyle as well as to physical activity. Prolonged strenuous exercise may also increase the risk of thyroid cancer in women.

Pigmentary characteristics, UV radiation exposure, and risk of non-Hodgkin lymphoma: a prospective study among Scandinavian women.

BACKGROUND: UV radiation and pigmentary characteristics may be associated with non-Hodgkin lymphoma (NHL) risk, but few prospective studies exist. We investigated these associations in a Norwegian-Swedish cohort. METHODS: The cohort included women ages 30 to 50 years at enrolment in 1991 to 1992. Host factors, and exposure to sun and artificial tanning devices in life-decades 0 to 50 years were collected by questionnaire. Relative risks (RR) with 95% confidence intervals (CI) were estimated by Poisson regression. RESULTS: Among 104,953 women with complete follow-up through 2006 (Sweden) and 2007 (Norway), 158 were diagnosed with NHL. Women with brown hair had an increased risk of NHL compared with dark brown-haired/black-haired women (RR, 1.72; 95% CI, 1.08-2.74); decreased risks were found among women with gray, green or mixed (RR, 0.50; 95% CI, 0.32-0.77), or blue (RR, 0.54; 95% CI, 0.35-0.81) eyes compared with those with brown eyes, and among those with high propensity to burn compared with those with low propensity (RR, 0.57; 95% CI, 0.36-0.91). Annual number of sunburns and bathing vacations in any age decade, or ever use of artificial tanning devices were not significantly associated with NHL risk. After exposure at ages 10 to 39 years, RRs for ever versus never exposed were 0.99 (95% CI, 0.65-1.50) for sunburn, 1.00 (95% CI, 0.64-1.54) for bathing vacations, and 0.99 (95% CI, 0.67-1.46) for artificial tanning device use. CONCLUSION: Whereas several pigmentary characteristics were associated with NHL risk, our results do not support an association between UV radiation and NHL. IMPACT: Studies of UV radiation and NHL are warranted for etiologic understanding and public health recommendations.

Sun and solarium exposure and melanoma risk: effects of age, pigmentary characteristics, and nevi.

BACKGROUND: Few prospective studies have analyzed solar and artificial (solarium) UV exposure and melanoma risk. We investigated these associations in a Norwegian-Swedish cohort study and addressed effect modification by age, pigmentary characteristics, and nevi. METHODS: The cohort included women ages 30 to 50 years at enrollment from 1991 to 1992. Host factors and exposure to sun and solariums in life decades were collected by questionnaire at enrollment. Relative risks (RR) with 95% confidence intervals (CI) were estimated by Poisson regression. RESULTS: Among 106,366 women with complete follow-up through 2005, 412 melanoma cases were diagnosed. Hair color and large, asymmetric nevi on the legs were strongly associated with melanoma risk (P(trend) < 0.001), and the RR for > or =2 nevi increased from brown/black to blond/yellow to red-haired women (RRs, 1.72, 3.30, and 4.95, respectively; P(interaction) = 0.18). Melanoma risk increased significantly with the number of sunburns and bathing vacations in the first three age decades (P(trend) < or = 0.04) and solarium use at ages 30 to 39 and 40 to 49 years [RRs for solarium use > or =1 time/mo 1.49 (95% CI, 1.11-2.00) and 1.61 (95% CI 1.10-2.35), respectively; P(trend) < or = 0.02]. Risk of melanoma associated with sunburns, bathing vacations, and solarium use increased with accumulating exposure across additional decades of life. CONCLUSIONS: Melanoma risk seems to continue to increase with accumulating intermittent sun exposure and solarium use in early adulthood. Apparently, super-multiplicative joint effects of nevi and hair color identify people with red hair and multiple nevi as a very high risk group and suggest important gene-gene interactions involving MC1R in melanoma etiology.

Metabolic profile, physical activity, and mortality in breast cancer patients.

Metabolic components [body mass index (BMI), blood pressure, serum lipids] and physical activity may affect biological mechanisms of importance for breast cancer prognosis. A population-based survival study among 1,364 breast cancer cases within the Norwegian Counties Study during 1974-2005 was conducted. Pre-diagnostic measurements of BMI, blood pressure, serum lipids, and self-reported physical activity were assessed. Multivariable Cox proportional hazard models were used in analyses (SAS version 9.11). Among these breast cancer cases (age at diagnosis 27-79 years), 429 women died (8.2 mean follow-up years). Those with a BMI >or= 30 kg/m(2) had a 1.47 higher risk of dying during follow-up than women with a BMI of 18.5-25 kg/m(2) [hazard ratio (HR) = 1.47, 95% CI 1.08-1.99]. Women with BMI < 25 kg/m(2) and age of diagnosis >or=55 years had a 66% reduction in overall mortality if they regularly exercised before diagnosis compared with sedentary women (HR = 0.34, 95% CI 0.16-0.71). Women in the highest tertile of total cholesterol had a 29% increase in mortality compared to women in the lowest tertile (HR = 1.29, 95% CI 1.01-1.64). Additionally, women in the highest tertile of blood pressure had a 41% increase in mortality compared to women in the lowest tertile of blood pressure (HR = 1.41, 95% CI 1.09-1.83). Our study supports a relationship between mortality not only in relation to BMI, but also blood pressure, lipids, and physical activity among breast cancer patients. These factors may all be important targets for invention among breast cancer patients.

Evaluation of three dietary assessment methods and serum biomarkers as measures of fruit and vegetable intake, using the method of triads.

The validity of fruit and vegetable intake estimated by 14 d weighed records, a twenty-seven-item food frequency questionnaire (FFQ) and a 180-item FFQ was investigated using serum carotenoids as the validity criterion. In addition, the method of triads was used to assess the validity of fruit and vegetable intake estimated from the FFQ and serum carotenoids. One hundred Norwegian men completed 14 d weighed records and the 180-item FFQ. Eighty-six of them also completed the twenty-seven item FFQ. The partial correlation coefficients between serum carotenoids and fruit and vegetable intake were slightly higher for the 14 d weighed records than for the two FFQ, but no difference was observed between the 180- and the twenty-seven item FFQ. The strongest correlations were observed between vegetable intake and serum alpha-carotene. The highest validity coefficients (VC) were observed for vegetable intake estimated from weighed records, the 180-item FFQ, the twenty-seven item FFQ and by the biomarker serum alpha-carotene, with VC of 0.77, 0.58, 0.51 and 0.67, respectively. In conclusion, the short FFQ gave as valid estimates for fruit and vegetable intake as the long FFQ. Both the estimated partial correlation coefficients and VC suggest that serum alpha-carotene is the best biomarker for intake of vegetable alone and total intake of fruit and vegetables in this population of Norwegian men, but the biomarkers did not perform any better than the FFQ.

Serum high-density lipoprotein cholesterol, metabolic profile, and breast cancer risk.

BACKGROUND: The prevalence of metabolic syndrome (obesity, glucose intolerance, low serum high-density lipoprotein cholesterol [HDL-C], high serum triglycerides, hypertension) is high and increasing in parallel with an increasing breast cancer incidence worldwide. HDL-C represents an important aspect of the syndrome, yet its role in breast cancer is still undefined. METHODS: In two population-based screening surveys during 1977-1983 and 1985-1987, serum HDL-C was assayed enzymatically among 38,823 Norwegian women aged 17-54 years at entry. Height, weight, blood pressure, serum lipids, fat and energy intake, physical activity, parity, oral contraceptive use, hormone therapy use, alcohol intake, and tobacco use were also assessed. We used Cox proportional hazards modeling to estimate the relative risk (RR) of breast cancer associated with serum HDL-C levels and to adjust for potential confounding variables. We performed stratified analyses to evaluate effect modification by body mass index (BMI) and menopausal status. All statistical tests were two-sided. RESULTS: During a median follow-up of 17.2 years, we identified 708 cases of invasive breast cancer. In multivariable analysis, the risk of postmenopausal breast cancer was inversely related to quartile of HDL-C (P(trend) =.02). Among women with HDL-C above 1.64 mmol/L (highest quartile) versus below 1.20 mmol/L (lowest quartile), the relative risk was 0.75 (95% confidence interval [CI] = 0.58 to 0.97). The HDL-C association was confined to women in the heavier subgroup (BMI > or =25 kg/m2), for whom the relative risk of postmenopausal breast cancer in those with HDL-C above 1.64 mmol/L versus below 1.20 mmol/L was 0.43 (95% CI = 0.28 to 0.67; P(trend)<.001; P(interaction) =.001). CONCLUSION: Low HDL-C, as part of the metabolic syndrome, is associated with increased postmenopausal breast cancer risk.

The efficacy of a treatment program focusing on specific stabilizing exercises for pelvic girdle pain after pregnancy: a two-year follow-up of a randomized clinical trial.

STUDY DESIGN: A randomized clinical trial. OBJECTIVES: To examine the effects of a treatment program focusing on specific stabilizing exercises after a 2-year follow-up period. SUMMARY OF BACKGROUND DATA: An individualized treatment approach with specific stabilizing exercises is shown to be effective for women with pelvic girdle pain 1 year after delivery. No previous study has examined the long-term effects of treatment for women with postpartum pelvic girdle pain. METHODS: Eighty-one women with pelvic girdle pain postpartum were assigned randomly to 2 treatment groups for 20 weeks. Patient self-reported questionnaires measuring pain, disability, and health-related quality of life were collected after 20 weeks of treatment and 1 and 2 years postpartum. RESULTS: All 81 women returned the questionnaires for the 2-year follow-up. Sixteen were excluded from the analysis, mainly due to new pregnancies. The significant differences between the groups in functional status, pain, and physical health (SF-36) were maintained 2 years after delivery. Minimal disability was found in 85% of the specific stabilizing exercise group as compared to 47% in the control group. The control group showed significant improvement in functional status with median change score of 6.0 (Q1-Q3 of -12-0). Minimal evening pain was reported by 68% in the specific stabilizing exercise group versus 23% in the control group. However, the group differences disappeared for all measures when controlling for score level 1 year after delivery by regression analysis. CONCLUSION: The significant differences between the groups persisted with continued low levels of pain and disability in the specific stabilizing exercise group 2 years after delivery. Significant reduction in disability was found within the control group. Those with the highest level of disability and greatest potential for improvements recovered most, regardless of intervention group.

A prospective study of pigmentation, sun exposure, and risk of cutaneous malignant melanoma in women.

BACKGROUND: Although sun exposure is an established cause of cutaneous malignant melanoma, possible interactions with host factors remain incompletely understood. Here we report the first results from a large prospective cohort study of pigmentation factors and sun exposure in relation to melanoma risk. METHODS: The Women's Lifestyle and Health Cohort Study included 106 379 women from Norway and Sweden who were aged 30-50 years in 1991 or 1992 when they completed an extensive questionnaire on personal characteristics and exposures. Linkages to national registries ensured complete follow-up through December 31, 1999. Poisson regression models were used to estimate relative risks (RRs). All statistical tests were two-sided. RESULTS: During an average follow-up of 8.1 years, 187 cases of melanoma were diagnosed. Risk of melanoma was statistically significantly associated with increasing body surface area (RR for > or =1.79 m2 versus < or =1.61 m2 = 1.60, 95% confidence interval [CI] = 1.03 to 2.48; P(trend) =.02), number of large asymmetric nevi on the legs (RR for > or =7 nevi versus 0 nevi = 5.29, 95% CI = 2.33 to 12.01; P(trend)<.001), hair color (RR for red versus dark brown or black = 4.05, 95% CI = 2.11 to 7.76; P(trend)<.001), sunburns per year at ages 10-19, 20-29, and 30-39 years (P(trend)<.001, P(trend) =.03, and P(trend) =.05, respectively), and use of a device that emits artificial light (solarium) one or more times per month (P =.04). CONCLUSIONS: Our results confirm previous findings that hair color, number of nevi on the legs, and history of sunburn are risk factors for melanoma and suggest that use of a solarium is also associated with melanoma risk. Adolescence and early adulthood appear to be among the most sensitive age periods for the effects of sunburn and solarium use on melanoma risk. However, it may be too early to see the full effect of adult exposures in this cohort.