Harmonic scalpel compared with conventional excisional haemorrhoidectomy: a meta-analysis of randomized controlled trials.

BACKGROUND: Haemorrhoidectomy is the most effective and definitive treatment for grade 3 or 4 haemorrhoids despite being associated with considerable pain. The aim of this study was to search the literature, which compares outcomes of harmonic scalpel haemorrhoidectomy and traditional surgical procedures, and conduct a quantitative meta-analysis of the randomized trials. METHODS: Randomized controlled trials (RCTs) were identified from the major electronic databases using the keywords "harmonic scalpel haemorrhoidectomy" and "haemorrhoidectomy" and a quantitative meta-analysis conducted. The eight trials that met the inclusion criteria included 468 patients (233 in the harmonic scalpel group). Pain was the primary outcome measure, and other parameters assessed included duration of operation, length of hospital stay, time to return to work, and complications. RESULTS: Significantly, more patients returned to work in the first post-operative week, and pain scores were an average of one unit lower following harmonic scalpel haemorrhoidectomy. Generally, the incidence of complications in the harmonic scalpel group was less than half that found in conventional haemorrhoidectomy. There was no significant difference between the groups as regards operating time or length of hospital stay. Recurrence was not reported in any of the studies. CONCLUSIONS: The meta-analysis showed that harmonic scalpel haemorrhoidectomy is a safe and effective modality associated with less post-operative pain and a more rapid return to work than traditional surgery for haemorrhoids. Statistical heterogeneity was high; thus, it may be too early to place complete confidence in these results. Further RCTs are required.

Are medical student results affected by allocation to different sites in a dispersed rural medical school?

INTRODUCTION: As medical education becomes more decentralised, and greater use is made of rural clinical schools and other dispersed sites, attention is being paid to the quality of the learning experiences across these sites. This article explores this issue by analysing the performance data of 4 cohorts of students in a dispersed clinical school model across 4 sites. The study is set in a newly established medical school in a regional area with a model of dispersed education, using data from the second to fifth cohorts to graduate from this school. METHODS: Summative assessment results of 4 graduating cohorts were examined over the final 2 years of the course. Two analyses were conducted: an analysis of variance of mean scores in both years across the 4 sites; and an analysis of the effect of moving to different clinical schools on the students' rank order of performance by use of the Kruskal-Wallis test. RESULTS: Analysis revealed no significant difference in the mean scores of the students studying at each site, and no significant differences overall in the median ranking across the years. Some small changes in the relative ranking of students were noticed, and workplace-based assessment scores in the final year were higher than the examination-based scores in the previous year. CONCLUSIONS: The choice of clinical school site for the final 2 years of an undergraduate rural medical school appears to have no effect on mean assessment scores and only a minor effect on the rank order of student scores. Workplace-based assessment produces higher scores but also has little effect on student rank order. Further studies are necessary to replicate these findings in other settings and demonstrate that student learning experiences in rural sites, while popular with students, translate into required learning outcomes, as measured by summative assessments.

Meta-analysis of survival of patients with stage IV colorectal cancer managed with surgical resection versus chemotherapy alone.

BACKGROUND There is no consensus regarding the appropriate management of asymptomatic and minimally symptomatic patients with stage IV colorectal cancer and irresectable metastases. METHODS A literature search was conducted on Medline and Embase. Outcome measures included: survival; postoperative morbidity and mortality; complications from the primary tumor and the need for surgery to manage complications; the likelihood of curative surgery after initial response to primary therapy; and length of hospital stay. Quantitative meta-analysis was performed where appropriate. RESULTS Eight retrospective studies, including 1,062 patients, met the criteria for inclusion in this study. Meta-analysis has shown an improvement in the survival of patients managed with palliative resection of their primary tumor, with an estimated standardized median difference of 6.0 months (standardized difference, 0.55; 95% confidence interval (CI), 0.29, 0.82; p < 0.001). Patients managed with chemotherapy alone were 7.3 times more likely to have a complication from the primary tumor (95% CI, 1.7, 34.4; p = 0.008). There was no difference in the response rates to chemotherapy, making metastatic disease amendable to curative resection (0.85; 95% CI 0.40, 1.8; p = 0.662). CONCLUSIONS To date, only retrospective data are available, showing that palliative resection of the primary tumor in asymptomatic or minimally symptomatic patients with stage IV colorectal cancer is associated with longer survival. Resection of the primary tumor reduces the likelihood of complications from the primary tumor and avoids the need for emergency procedures.

Better psychological health is associated with weight stability in women with eating disorders.

AIM: To explore the associations between changes in weight, eating disorder psychopathology and psychological distress in a community sample of women with eating disorders over two years. METHOD: One hundred and twenty two women identified with disordered eating in a baseline population survey agreed to participate in a follow-up study, of whom 87 (71%), mean age 28+/-6.2, completed the two-year follow-up. Body mass index, eating disorder psychopathology, psychological distress, and demographic details were assessed at both time points. RESULTS: Over the two years there was a mean weight gain of 1.76 kg (SD=7.03), 11 (13%) women lost > or =5 kg, 25 (29%) gained > or =5 kg, and 49 (58%) remained weight stable (i.e., within 5 kg of baseline weight). Comparisons between those who had lost, gained and remained weight stable showed few significant differences, however, women who remained weight stable were the least psychologically distressed at baseline and those who lost weight had the greatest reduction in shape concern. Body mass index at baseline, and change in level of binge eating episodes were not associated with weight change. CONCLUSIONS: Disordered eating behaviours have little influence on weight change over two years in community women with disordered eating. Low levels of psychological distress at baseline may promote weight stability. Concerns about shape are likely to increase with increased weight.

Updated meta-analysis of randomized controlled trials comparing conventional excisional haemorrhoidectomy with LigaSure for haemorrhoids.

BACKGROUND: To compare the surgical outcome of haemorrhoidectomy performed using LigaSure bipolar diathermy with conventional haemorrhoidectomy. METHODS: Only randomized and alternate allocated studies were included from the major electronic databases using the search terms "ligasure" and "haemorrhoids". Duration of operation, blood loss during operation, postoperative pain score, wound healing, in-hospital stay, time to return to normal activities and complications were assessed. RESULTS: The 11 trials contained a total of 1,046 patients; the largest study was based on 273 patients and two earlier studies were based on 34 patients. No significant gender mismatch between the groups was reported in any of the studies. The patients' ages were similar between groups in the studies, as was disease severity. All 11 studies reported a shorter duration of the operation when using LigaSure compared to the conventional technique (p<0.001). The postoperative pain score (p=0.001) and blood loss during operation (p=0.001) were significantly reduced. After LigaSure haemorrhoidectomy wound healing (p=0.004) and the return to normal activities (p=0.001) were significantly faster than after conventional haemorrhoidectomy. However, the overall incidence of complications reported was not significantly different (p=0.056). CONCLUSIONS: LigaSure is an effective instrument for haemorrhoidectomy which results in less blood loss, quicker wound healing and earlier return to work.

Accuracy of clinical diagnosis of skin lesions.

BACKGROUND: Skin cancer is an increasing problem in fair-skinned populations worldwide. It is important that doctors are able to diagnose skin lesions accurately. OBJECTIVES: To compare the clinical with the histological diagnosis of excised skin lesions from a set of epidemiological data. We analysed diagnostic accuracy stratified by histological subtype and body site and examined the histological nature of misclassified diagnosis. METHODS: All excised and histologically confirmed skin cancers in Townsville/Thuringowa, Australia from December 1996 to October 1999 were recorded. Positive predictive values (PPVs) and sensitivities were calculated for the clinical diagnoses and stratified by histological subtype and body site. RESULTS: Skin excisions in 8694 patients were examined. PPVs for the clinical diagnoses were: basal cell carcinoma (BCC) 72.7%; squamous cell carcinoma (SCC) 49.4%; cutaneous melanoma (CM) 33.3%. Sensitivities for the clinical diagnosis were: BCC 63.9%; SCC 41.1%; CM 33.8%. For BCC, PPVs and sensitivities were higher for the trunk, the shoulders and the face and lower for the extremities. The reverse pattern was seen for SCCs. CONCLUSIONS: Diagnostic accuracy was highest for BCC, the most prevalent lesion. Most excisions were correctly diagnosed or resulted in the removal of malignant lesions. With nonmelanocytic lesions, doctors tended to misclassify benign lesions as malignant, but were less likely to do the reverse. Although a small number of clinically diagnosed common naevi subsequently proved to be melanoma (6.3%), a higher proportion of all melanomas had been classified as common naevi (20.9%). Accuracy of diagnosis was dependent on body site.

Open compared with closed haemorrhoidectomy: meta-analysis of randomized controlled trials.

AIMS: This review compares the most popular techniques in managing the wounds after excisional haemorrhoidectomy, which are either to lay the wounds open or to close them. METHODS: Randomized controlled trials were identified from the major electronic databases using the search terms "hemorrhoid*" and "haemorrhoid*." Duration of operation, pain, length of hospital stay, time off work, time for wound healing, patient satisfaction, continence, manometry findings and complications were assessed. Quantitative meta-analysis was performed as appropriate or possible. RESULTS: Six trials including 686 patients met the inclusion criteria. The median follow-up time ranged from 1.5 to 19.5 months. Quantitative meta-analysis showed that there was no significant difference in cure rates between the two techniques (relative risk, 1.4; 95% CI, 0.86 to 2.2; p=0.191). Open haemor-rhoidectomy was more quickly performed (weighted mean difference, 1.03 min; 95% CI, 0.51 to 1.54; p<0.001). Closed haemorrhoidectomy wounds showed faster healing (weighted mean difference, 1.2 weeks; 95% CI, 0.88 to 1.55; p<0.001). Hospital stay, maximum pain score, total and individual complication rates were not significantly different. CONCLUSIONS: Apart from faster wound healing after closed haemorrhoidectomy, open and closed techniques appeared equally effective and safe. However, there were only a few studies which presented information in different ways, and statistical heterogeneity was high.

Basal cell carcinoma: histological classification and body-site distribution.

BACKGROUND: Basal cell carcinoma (BCC) is the most common cancer worldwide in white-skinned populations. Recent studies suggest that BCC is not a single entity and that different histological subtypes show different clinical behaviour and might have different aetiology. OBJECTIVES: To provide information on the incidence of BCC by histopathological subtype and body site. METHODS: A case series of BCC from a prospective population-based register study collecting information on all excised and histologically confirmed skin cancers in Townsville, north Australia between 1997 and 1999. RESULTS: Age-standardized incidence rates for nodular BCC were 727.1 per 100 000 inhabitants per year for males and 411.8 for females, while rates for superficial BCC were 336.5 for males and 251.4 for females. Incidence rates for 'high risk' BCC were 261.3 for males, 146.5 for females with infiltrative, and 156.7 for males and 100.2 for females with micronodular types. Superficial BCC occurred at a younger age, particularly in female patients. For all histological subtypes and both genders relative tumour density was highest for the face, followed by the neck. An exception was superficial BCC in males, where the posterior trunk was second, followed by the neck. CONCLUSIONS: The study found a higher rate of superficial BCC than previous studies from less sun-exposed countries, and a more equal distribution of superficial BCC on face, trunk and limbs. These results seem to blur the difference between intermittent and continuous sun exposure as the causative environmental agents. The clinical implications of 'high risk' BCC rates are discussed.

Why paediatricians rural out going to the country but support opportunities for change.

OBJECTIVES: To determine the knowledge of vacant country specialist positions, the main barriers to filling country specialist positions, the acceptance of hypothetical creative employment models and to gain understanding of what would it take for respondents to accept a country position. METHODOLOGY: Mailed self-report questionnaires to all 103 Queensland paediatricians and finishing paediatric trainees (response rate 93.1%) to explore reasons for the long-term vacancy of the Staff Paediatrician position at the Mount Isa Base Hospital, North-west Queensland, Australia. RESULTS: Of the respondents, 87.4% were aware of the vacant position. The lack of adequate locum cover for leave (97.8%), on-call load (92.2%), professional isolation (91.4%), and family commitments (91.4%) were identified as the four most frequently recognized recruitment barriers. Of the respondents, 30.2% said they could be attracted to such a position if they were guaranteed the ability to return to their present post in 2 years, 30.7% said they could be attracted to a rural exchange, and 73.1% suggested the position would be more attractive to new Fellows if at the end of a 2-year period they were guaranteed some Visiting Medical Officer sessions or a temporary Staff Paediatrician position at a tertiary centre. Significantly, fewer of the 30-39-years age group said available job opportunities for their spouse made it impossible for them to consider the advertised position, compared to older age groups (P = 0.003). In response to the question 'What would it take for you to consider such a position?', 22.6% answered a change in employment package, 22.6% a change in family commitments, 16.6% too subspecialized, and 7.1% could possibly consider a locum or exchange in the future. CONCLUSIONS: Specialist positions, such as the advertised position, are well known, but remain unfilled because they are considered unsustainable. However, the response to hypothetical creative employment models suggests this could be changed, provided specialist training (e.g. paediatric training) is kept general and the younger consultant is given consideration.

Maternal awareness of sudden infant death syndrome in North Queensland, Australia: an analysis of infant care practices.

OBJECTIVES: To assess awareness of sudden infant death syndrome (SIDS) and risk reducing recommendations in a sample of mothers in North Queensland, Australia, and to examine their infant care practices. METHOD: Interviews conducted with 195 women using a standardized questionnaire between October 1997 and January 1998. RESULTS: 191 questionnaires analyzed; 134 (70.2%) Caucasian and 57 (29.8%) indigenous women. Four women with previous SIDS experience were excluded from the analysis. Eight (4.2%) had never heard of SIDS. Twenty-nine (15.2%) had heard of SIDS and 154 (80.6%) had heard of SIDS and could list risk recommendations to reduce its incidence. Multivariate analysis identified ethnicity as the only significant predictor of maternal knowledge. Indigenous mothers knew less about SIDS: adjusted odds ratio (OR) = 5.4; 95% confidence interval (CI) = [2.1-14.0]. Avoidance of prone sleeping was the most frequently identified recommendation (n = 132), with no smoking in pregnancy (n = 48) and breastfeeding (n = 40) identified least frequently. There were 80.2% of mothers who put their infant in non-prone positions to sleep. Only 48 (25%) women identified smoking in pregnancy, and 93 (48.6%) smoking in the infant's environment as risk factors. Indigenous women were more likely to smoke in their pregnancy (P = 0.004), bed share with their infant (P = 0.0001), and have smokers in the home. CONCLUSION: There is a high level of awareness of SIDS and the main associated risk factor of infant prone sleeping, but the link between SIDS and smoking requires further emphasis. Future campaigns should ensure the SIDS message is delivered more effectively to the indigenous communities.

Time trends of cutaneous melanoma in Queensland, Australia and Central Europe.

BACKGROUND: The objective of this study was to describe recent developments in cutaneous melanoma from the German speaking countries in Europe (Germany, Austria, and Switzerland) and from Queensland, Australia. METHODS: All incident invasive cutaneous melanoma cases recorded between 1986 and 1996 by the Queensland Melanoma Register and by the Central Malignant Melanoma Registry of the German Dermatological Society were included in the analysis. Weighted linear trend analyses were performed to assess significant changes over the years using yearly sample sizes as weights. RESULTS: In Central Europe, the median tumor thickness decreased from 1.2 mm in 1986 to 0.8 mm in 1996 (P < 0.001), whereas it varied insignificantly between 0.5 mm and 0.6 mm in Queensland. The percentage of patients with Clark Level II invasion increased significantly in Queensland (P < 0.001; 1996, 61.1%) and in Central Europe (P = 0.041; 1996, 24.5%). The percentage of superficial spreading melanomas rose in Central Europe (P = 0.043; 1996, 64.4%), whereas it decreased slightly in Queensland (P = 0.032; 1996, 75%). In Queensland and in Central Europe, younger people and women presented more frequently with thinner melanomas (

Predictors of the use of sunscreen in dermatological patients in Central Europe.

BACKGROUND: There is mounting evidence that sun exposure is a cause of skin cancer. Therefore, the focus of skin cancer prevention is on sun protection. The present study investigated the use of sunscreens in a sample from the adult Central European population. METHODS: As part of a case-control study of cutaneous melanoma, a total of 498 controls with classical dermatological disorders were selected from hospitals in Central Europe. All people underwent whole-body skin examinations and were interviewed using a standardized questionnaire. RESULTS: Overall, 40.8% of the people never used sunscreen and of the 281 persons who used sunscreen, 41.5% applied it only once per sun bath. Persons who did not use sunscreen tended to be older (P<0.0001) and of male gender (P = 0.0004). Young people, women, and people who expressed a positive attitude to the sun spent more time in the sun and were more likely to apply sunscreens. People who worked almost always outdoors had a six times increased odds ratio of not using sunscreens (P<0.0001) compared to people who worked always indoors. CONCLUSIONS: Men, older people, and outdoor workers should be targeted in health education campaigns. On the other hand, people who apply sunscreen as a means of sun protection should be advised about adequate usage.

Agreement between self-assessment of melanocytic nevi by patients and dermatologic examination.

The number of melanocytic nevi is the strongest risk factor for cutaneous melanoma. As pigmented skin lesions are visible to everybody, the question has been raised about whether people can identify themselves as being at risk for melanoma through self-counting of moles. In 1991, a total of 513 central European melanoma patients and 498 controls were asked to count the total number of nevi and the number of atypical nevi on the whole body. Whole-body examination by dermatologists followed. Agreement was assessed on categorized nevus counts by means of ordinal kappa values and log-linear modeling. Study subjects significantly underestimated the total number of melanocytic nevi (p < 0.0001). Chance-corrected overall agreement was rather poor (kappa = 0.14), and the ability to detect many existing nevi was low. Agreement was higher for atypical melanocytic nevi counts (kappa = 0.37), and the sensitivity to detect more than one atypical nevus was 0.48. Self-assessment of the number of melanocytic nevi was difficult to perform accurately, and people severely underestimated the actual number. Despite these results, people should be encouraged to perform regular skin self-examination for early detection of melanoma.

An educational intervention to improve diagnosis and management of suspicious skin lesions.

BACKGROUND: Family physicians have an important clinical role in assessment and management of suspicious skin lesions. As a result of a previous needs assessment study, an educational intervention based on audit and feedback with opportunity for reflection on practice was introduced to 46 family physicians randomly allocated to either an intervention (23) or control group (23). As an educational tool, audit allows doctors to systematically review their practice and establish the quality of care they provide. When combined with feedback and comparison of clinical performance with peers or standards, it has been shown to increase learning and change behavior. METHODS: Data based on their own patients, on the correlation between clinical and histologic diagnosis, and excisions of skin lesions were collated and reported to the intervention group. RESULTS: Despite randomization of the doctors, the patient population of doctors in the intervention and control groups were significantly different in key characteristics, including the types of skin lesions treated. The intervention group of doctors showed improved performance in providing clinical information on pathology requests and in adequate surgical excision of skin lesions. Diagnostic performance did not improve significantly, but physicians' certainty of diagnosis did. IMPLICATIONS: This study design has highlighted the difficulty in balancing the use of evidence-based educational strategies in an equivalent setting to normal practice with evaluation of performance using measures that include characteristics of practitioners' patients that cannot be controlled.

Why do mothers still sun their infants?

OBJECTIVE: To determine the prevalence of maternal beliefs about the therapeutic uses of sunlight in infancy in tropical Australia. METHODOLOGY: Data were collected by interviewing 114 post-partum patients in Townsville (19 degrees 16'S), Queensland. Each woman was asked a series of open-ended and set-response questions about ancestry, pigmentation, residential history, parity, maternal and paternal education, and beliefs regarding the reputed therapeutic uses of sunlight. RESULTS: Half of the women had at least one risky belief about the perceived benefits of sunning their baby. Thirty-six per cent were in favour of using sunlight to treat neonatal jaundice; 20.2% believed it was necessary to intentionally sun their baby to prevent vitamin D deficiency; and 10.5% thought sunlight was a good remedy for nappy rash. Independent predictors of one or more of these beliefs included maternal age and education level, and having another child that had been treated for jaundice. Forty per cent of multiparous women had sunned a child to treat neonatal jaundice. In most cases, advice to mothers to sun their baby had been given by a midwife/nurse (41% or a doctor/paediatrician (28%). CONCLUSIONS: Post-parturient women had a high prevalence of beliefs that may result in their infant being intentionally exposed to sunlight, and which could increase their child's future risk of skin neoplasia. Midwives and doctors, including paediatricians, were identified as the major professional sources of these beliefs. Professional education is needed to change the beliefs of health professionals who recommend therapies involving sunlight.

Head lice in pupils of a primary school in Australia and implications for control.

BACKGROUND: Anecdotal reports suggest that head lice infestations are a common problem in school-aged children in Australia; however, only a few data are available. The present study aimed to determine the prevalence of infestation with head lice in children in an urban Australian school. METHODS: All 735 pupils from grades preschool to five of a government run primary school were invited to participate in the cross-sectional survey. Overall, 212 boys (46.5%) and 244 girls from 29 classes were examined. The main outcome measures were: (1) the detection of lice or eggs by visual examination of the child's head, and classification into 'not infested' and 'infested;' infested cases were further classified into 'active infestation' (lice or viable eggs found) or 'inactive infestation' (only unhatched eggs found); (2) for each child, a parent or guardian was asked to complete a standardized questionnaire. RESULTS: Of the 456 children examined, 33.7% (95% confidence interval = 95%-CI = [26.9%, 40.4%]) had evidence of infestation with head lice, 21.0% (95%-CI = [15.2%, 26.8%]) with active infestation. The prevalence of infestation (active plus inactive) varied greatly between classes, ranging from zero to 72.2% (p < 0.001). Head lice were more prevalent in girls than boys (p < 0.001). Analysis of questionnaires showed that 47.7% (95%-CI = [43.0%, 52.4%]) of the children had been infested with head lice in the previous 6 months. For children with active pediculosis capitis on examination, 14.0% (95%-CI = [7.9%, 22.4%]) of parents or guardians had not noticed the infestation. CONCLUSIONS: In an urban primary school in Australia, head lice infestation was present at a hyperendemic level. Clustering by class indicated the classroom as a main source of infestation. Control strategies implemented in schools and including the education of teachers and parents need to be evaluated.

Body-site distribution of melanocytic nevi in young Australian children.

OBJECTIVE: To investigate the body-site distribution of melanocytic nevi (MN) with respect to habitually and intermittently sun-exposed surfaces. DESIGN: Cross-sectional survey of MN prevalence. SETTING: Townsville (19.16 degrees S), Queensland, Australia. PARTICIPANTS: Random sample of 506 1- to 6-year-old white children who were born and raised in Townsville (response, 87.6%). MAIN OUTCOME MEASURES: Site-specific counts and densities (number per square meter) of MN. RESULTS: Densities of MN of all sizes were highest on the outer forearms, followed by the outer upper arms, neck, and face. The feet had the lowest density of MN. Densities of MN of 2 mm or greater were highest on the upper arms and trunk. Boys had higher densities of MN of all sizes on the neck than girls (P = .002). Girls had higher densities of MN of 2 mm or greater on the lower legs (P = .006) and thighs (P = .005) than boys. Habitually sun-exposed body sites had higher densities, particularly of small MN, than relatively sun-protected sites, and larger MN were most prevalent on the intermittently exposed skin of the trunk. CONCLUSIONS: These children have higher total body and site-specific MN counts and densities than children from elsewhere, and their MN are distributed over the body in a way that implicates exposure to sunlight. As sun exposure in childhood and MN are risk factors for melanoma, intervention studies are required to determine if MN can be prevented.

Incidence rates of skin cancer in Townsville, Australia.

Worldwide, incidence rates of skin cancer are increasing alarmingly in populations of predominantly Caucasian origin. A prospective population-based survey, set up to collect epidemiological information on all excised and histologically confirmed skin cancers, started in Townsville, Australia (population of 127,000) in December 1996. Data on the anatomical distribution of skin cancer has been collected using a detailed body map. Estimations of type-specific and site-specific incidence rates were age-standardized according to world standard population. Site-specific incidence rates were adjusted for surface proportion of the body site and are given per 100,000 body units. Between December 1996 and December 1997, a total of 3,536 patients with 5,945 histologically confirmed skin cancer lesions were recorded. Age-standardized incidence rates of basal cell carcinoma were 2,058.3 for men and 1,194.5 for women, 1,332.3 for men and 754.8 for women for squamous cell carcinoma, and 49.1 for men and 41.7 for women for cutaneous melanoma (CM). Site-specific incidence rates of non-melanocytic skin cancer were extreme on sun-exposed areas of the face, whereas site-specific incidence rates of CM were highest for neck, posterior trunk and face. Less exposed body sites, such as unexposed upper limbs or thighs, showed reduced incidence rates for all types of skin cancer. Tropical North Queensland has the world's highest incidence rates of skin cancer of all types. Site-specific incidence rates demonstrate that highly sun-exposed body sites are at high risk of developing skin cancer and provide, therefore, strong indirect evidence for the causal relationship between sun exposure and skin cancer.