Biomedical subjects

L D Marrett

Publications and source records attributed to L D Marrett.

At least 19 recordsLinked to original sources

PubMed2002

Coffee and tea consumption and cancers of the bladder, colon and rectum.

Coffee has been observed to be associated weakly or not at all with bladder cancer risk, inversely with colon cancer risk, and inconsistently with rectal cancer risk. The association between these cancers and consumption of coffee and tea was examined in a single case-control study conducted in Ontario, Canada from 1992 to 1994. A questionnaire was filled out by 927 bladder cancer cases, 991 colon cancer cases, 875 rectal cancer cases, and 2118 population controls. Although bladder cancer risk was not associated with coffee or tea, risk estimates associated with coffee among subjects who had never smoked were non-significantly increased. Colon cancer risk was inversely associated with coffee. Relative to those drinking less than 1 cup of coffee per day, the odds ratios (OR) for those drinking 1-2 cups was 0.9 (95% CI 0.8-1.1), for those drinking 3-4 cups was 0.8 (95% CI 0.7-1.0), and for those drinking 5 or more cups was 0.7 (95% CI 0.5-0.9); these ORs decreased linearly (P = 0.008). The reduced risk estimates were more pronounced with cancer of the proximal colon than the distal colon. Rectal cancer risk was not associated with either coffee or tea. Coffee consumption was observed to have a different relationship for each of the cancer sites and tea consumption was not related to any cancer site.

Case-Control Studies↗

PubMed2001

Trends in the incidence of cutaneous malignant melanoma in New South Wales, 1983-1996.

The incidence of cutaneous malignant melanoma (CMM) has been rising in fair-skinned populations throughout the world for decades. The upward trend may, however, finally be slowing in some of these populations. Recent (1983-1996) CMM incidence trends for a high incidence area (New South Wales, Australia) have been examined according to gender, age group, body site and tumour thickness. Despite continuing upward trends in older age groups, particularly among men (e.g., 7.20% increase per year in men aged 75+), incidence for younger ages is stabilizing (in men) or declining (in women): average annual percentage changes of -3.03 and -0.88 were observed for women aged 15-34 and 35-54, respectively. Patterns suggest a birth-cohort effect, with those born since 1945 or 1950 having lower (females) or similar (males) rates to those born earlier. For each gender, all-ages incidence rose by a similar amount for each of the main body sites except the leg in women, where incidence fell by 0.49% per year. In men, the incidence of both thin (</=75 mm) and thick (>75 mm) melanomas increased (significantly, by 2.63% per year and non-significantly, by 0.93% per year, respectively) between 1989 and 1996. In women, incidence remained stable for both thickness subgroups. These data are consistent with a stabilization or reduction in either total sun exposure or intermittency of exposure among New South Wales cohorts born since about 1950. Because incidence rates are still much higher than they were a few decades ago, however, efforts to reduce sun exposure, particularly in children and youth, must continue.

Adolescent↗

PubMed2001

Association of perforation of the appendix with female tubal infertility.

Although perforation of the appendix is considered a risk factor for female tubal infertility, the epidemiologic evidence supporting this relation is inconsistent. Risk factors for tubal infertility were compared for 121 women with documented primary tubal infertility attending in vitro fertilization clinics in Toronto, Canada, from July to December 1998 and 490 controls who were pregnant during the same time period. Self-administered questionnaires and review of medical records were used to assess exposures. The authors found that neither history of acute appendicitis nor perforation of the appendix was a statistically significant risk factor for tubal infertility. The crude odds ratio for perforated appendicitis was 3.4 (95% confidence interval (CI): 0.9, 12.9), and the adjusted odds ratio was 1.4 (95% CI: 0.3, 6.2). In addition to increased age and annual income, cigarette smoking (odds ratio (OR) = 2.0, 95% CI: 1.2, 3.2), history of endometriosis (OR = 6.0, 95% CI: 2.8,12.8), and history of pelvic inflammatory disease (OR = 6.0, 95% CI: 2.8, 12.8) were significantly associated with tubal infertility in multivariate analysis. These data do not provide substantial evidence that perforation of the appendix is an important risk factor for female tubal infertility.

Adult↗

PubMed2001

Predictors of sunburn among Canadian adults.

BACKGROUND: Data from the 1996 National Survey on Sun Exposure & Protective Behaviors (4,023 respondents) were analyzed to identify independent predictors of sunburn among adult Canadians. METHODS: Multivariate models predicting sunburn odds were developed using unconditional logistic regression. Backward elimination model selection was used to identify independent predictors of sunburn. RESULTS: Nonbehavioral characteristics found to predict sunburn were younger age, male sex, light skin color, nonblack hair color, and birthplace in North America or Europe. Behavioral predictors of sunburn included high awareness of the UV Index, working outdoors in the summer, longer leisure time in the sun, forgetfulness about protecting oneself from the sun, and seeking a tan. Sun avoidance between 11 AM and 4 PM was associated with lower odds of sunburn, while seeking shade when outside and use of protective clothing showed nonsignificant associations with lower sunburn odds. Sunscreen use was found to have a nonsignificant positive association with sunburn. CONCLUSIONS: These findings highlight risk factors to be considered in the targeting of sunburn reduction strategies to high-risk groups and suggest that sun avoidance, seeking shade, and use of protective clothing may be effective in preventing sunburn.

Adolescent↗

PubMed2001

Workshop report: identification of research needs breast cancer etiology.

A workshop to evaluate the scientific evidence for the etiologic associations between modifiable lifestyle and environmental risk factors and to identify areas for future research in breast cancer etiology was sponsored jointly by the Canadian Breast Cancer Initiative and the Canadian Breast Cancer Research Initiative in May, 2001. Reviews of the scientific evidence in these topics were commissioned and an expert panel convened to consider the reviews and make recommendations for research. The panel concluded that there was substantial evidence to proceed with additional research in several areas of breast cancer etiology. Particular support for future research for several lifestyle and environmental risk factors including alcohol, diet, physical activity, anthropometric factors, hormonally active agents and occupational exposures was identified. Several emerging hypotheses for breast cancer etiology were also considered and recommendations made in these areas. Specific areas for future consideration included: insulin-like growth factors, pharmaceuticals, viruses, psychosocial factors, and functional polymorphisms. The panel also identified common themes for future research including: studies of exposures across the life cycle; research in populations with unusual exposure levels; consideration of effect modification; development of improved exposure assessment methods and use of intermediate endpoints; separation of disease subtypes by hormone receptor status, stage and tumour markers; and consideration of biological mechanisms in breast cancer etiology.

Biological Factors↗

PubMed2000

Pre-natal and peri-natal exposures and risk of testicular germ-cell cancer.

The present case-control study was undertaken to investigate the association between exposure to maternal hormones and risk of testicular germ-cell cancer by histologic subgroups. Cases were males, aged 16 to 59 years, diagnosed with testicular germ-cell cancer in Ontario between 1987 and 1989. Histologic review was performed on all eligible cases for the purpose of categorizing cases as seminoma or non-seminoma (the latter classified 2 ways, with and without tumors containing seminoma). Risk factor data were collected on 502 cases, 346 case mothers, 975 age-matched controls, and 522 control mothers. Exogenous hormone exposure was associated with elevated risk (OR = 4.9, 95% CI 1.7-13.9). Several additional risk factors were associated with risk of testicular cancer: bleeding and threatened miscarriage (OR = 0.6, 95% CI 0.3-1.0), maternal cigarette smoking (12+ cigarettes/day OR = 0.6, 95% CI 0. 4-1.0). pre-term birth (OR = 1.6, 95% CI 1.0-2.5), and treatment for undescended testicle (OR = 8.0, 95% CI 3.2-20.0). First births were associated with elevated risk (OR = 1.7, 95% CI 1.0-2.8) among mothers below the age of 24 years at conception. There was little evidence that risk factors differed by histologic subgroup. We found evidence that exposure to maternal hormones, particularly estrogens, is associated with testicular germ-cell cancer risk. Not only does exposure to elevated levels (exogenous hormone use, pre-term birth, and first births among young mothers) increase risk but also exposure to relatively lower levels (heavy cigarette consumption and, perhaps, bleeding and threatened miscarriage) may decrease cancer risk.

Abortion, Threatened↗

PubMed2000

Do larger people have more naevi? Naevus frequency versus naevus density.

BACKGROUND: It is unclear which of the number or the density of naevi on the skin is the more appropriate measure of risk of melanoma. Furthermore, the relationship between the number of naevi and their density in an individual has not been explored. Thus, for example, it is unknown if larger people tend to have more naevi by virtue of having a larger skin area, or if the density of naevi is similar in people of different body sizes. In this study, we explored the relationship between the number and the density of naevi in a sample of adolescents. SUBJECTS AND METHODS: A sample survey of naevi in 472 grade 9 secondary school students (aged 14-15 years) was conducted in Tasmania, Australia during 1992, and a subset of these individuals was followed up in 1997. Counts of naevi of various sizes were taken on the arm, leg, and back. Naevus density was estimated by using an algorithm to estimate body surface area from the height and weight of an individual. More general relationships of the naevus counts to height and weight were also explored. Finally, we considered whether the relationship between naevus density and the anthropometric variables could be confounded by exposure to ultraviolet radiation. RESULTS: The mean number of naevi was very similar in the two samples. Naevus density was slightly lower in the 1997 sample, mainly because of increasing body size in the cohort. The numbers of naevi were only weakly related to height and weight in males, and there was essentially no relationship in females. Regression analysis showed significant relationships of weight to the back naevus counts in males in 1992 and 1997, and to the arm naevus count in males in 1997; otherwise, none of the regression coefficients for height and weight were statistically significant. This picture did not change following adjustment for potentially confounding variables indicating time spent outdoors or in the sun. Furthermore, there was no evidence that time spent in the sun was related to the body mass index. CONCLUSIONS: It appears that the number and density of naevi in an individual are unrelated. Accordingly, with the present state of knowledge concerning the risk of melanoma, both the number and density of naevi should be considered as equally valid in future studies as markers of the risk of melanoma, and in studies on the natural history of naevi. If the disease mechanism is systemic, and not related to particular naevi, naevus density might form the better marker of risk. However, if the disease mechanism is related to effects on particular naevi, then the risk would vary in proportion to the number of naevi.

Adolescent↗

PubMed2000

Pregnancy outcomes in females after treatment for childhood cancer.

This Ontario province-wide cohort study was conducted to compare the risk of adverse pregnancy outcomes in female childhood cancer survivors who received abdominal-pelvic radiation and/or chemotherapy with alkylating agents with the risk among those who were treated by non-sterilizing alkylating agents with the risk among those who were treated by non-sterilizing surgery only. Females in Ontario, Canada, diagnosed in 1964-1988 before age 20 with a histologically confirmed malignancy and who had survived for at least 5 years, attained age 18, and were alive at the time of study, were identified through the Ontario Cancer Registry. We ascertained pregnancy outcomes by a telephone-administered questionnaire. Treatment data were abstracted from medical records for 830 subjects 18-49 years of age, the analysis comprised 340 survivors who had one or more pregnancies after treatment. There was no evidence of an increased risk of having a spontaneous abortion or an infant with a birth defect. Survivors receiving abdominal-pelvic radiation were more likely to have a low birth weight infant (odds ratio estimate [OR] = 3.64; 95% confidence interval [CI] = 1.33-9.96), a premature low birth weight infant (OR = 3.29; 95% CI = 0.97-11.1), or an infant who died in the perinatal period (OR = 2.41; 95% CI = 0.50-11.5), compared with those receiving surgery. Risks of perinatal death and having a low birth weight infant increased with dose of radiotherapy directed to the abdomen.

Adult↗

PubMed2000

Case-control study of colon and rectal cancers and chlorination by-products in treated water.

This population-based case-control study was conducted in southern Ontario, Canada from 1992 to 1994 to assess the relationship between chlorination by-products in public water supplies and cancers of the colon and rectum. Interviews providing residence and water source histories were completed by 76% of eligible cancer cases and 72% of eligible controls. Supplemental data from municipal water supplies were used to estimate individual exposure to water source, chlorination status, and by-product levels as represented by trihalomethanes (THMs) during the 40-year period before the interview. The analyses included 767 colon cases, 661 rectal cases, and 1545 controls with exposure information for at least 30 of these years (75% of subjects with completed interviews). Among males, colon cancer risk was associated with cumulative exposure to THMs, duration of exposure to chlorinated surface water, and duration of exposure to a THM level > or = 50 microg/liter and 75 microg/liter. Males exposed to chlorinated surface water for 35-40 years had an increased risk of colon cancer compared with those exposed for < 10 years (odds ratio, 1.53; 95% confidence interval, 1.13-2.09). Males exposed to an estimated THM level of 75 microg/liter for > or = 35 years had double the risk of those exposed for < 10 years (odds ratio, 2.10; 95% confidence interval, 1.21-3.66). In contrast, these relationships were not observed among females. No relationship was observed between rectal cancer risk and any of the measures of exposure to chlorination by-products. The results of this study should be interpreted with caution because they are only partially congruent with the limited amount of literature addressing this issue.

Adult↗

PubMed2000

Workshop report: physical activity and cancer prevention.

A workshop to evaluate the evidence for the role of physical activity in cancer prevention and to identify priorities for action, particularly in relation to the primary prevention of cancer, was held by Cancer Care Ontario in March 2000. A review of the scientific evidence was commissioned and an expert panel convened to consider the review report and to make recommendations for public health, research and intervention. The panel concluded that evidence was convincing for the role of physical activity in preventing colon cancer; probable for breast cancer; possible for prostate cancer and insufficient for other sites. It is recommended that physical activity messages promoting at least 30 45 minutes of moderate to vigorous activity on most days of the week be included in primary prevention interventions for cancer. The panel recommended that future research on physical activity incorporate comprehensive assessments, including measures of the multiple dimensions and types of physical activity; biological mechanisms; and behavioural and population factors. Cancer Care Ontario will incorporate physical activity messages in its primary prevention programming around nutrition and health body weight.

Canada↗

PubMed1999

Early menopause and infertility in females after treatment for childhood cancer diagnosed in 1964-1988 in Ontario, Canada.

This study was conducted to determine the risk of menopause and infertility in female childhood cancer survivors who received abdominal-pelvic radiation and/or chemotherapy with alkylating agents in comparison with those who were treated by nonsterilizing surgery only. Females who were diagnosed in 1964-1988 before age 20 years with a histologically confirmed malignancy and who had survived for at least 5 years, had attained age 18, and were alive at time of study were identified through the Ontario Cancer Registry. Reproductive outcomes were ascertained by a telephone-administered questionnaire, and treatment data were abstracted from medical records for 830 subjects aged 18-49 years; 719 survivors who were nonmenopausal at the end of treatment were included in the analyses. Survivors who received both alkylating agents and abdominal-pelvic radiation were more likely to be postmenopausal than were those who underwent surgery (risk ratio = 2.58; 95% confidence interval: 1.14, 5.80). Women treated with abdominal-pelvic radiation alone had a fertility deficit of 23% compared with those in the surgery group; the deficit was restricted to women diagnosed postpuberty. Risks of menopause and infertility increased with increasing dose of abdominal-pelvic radiation and amount of alkylating agent.

Abdomen↗

PubMed1999

Trends in the incidence of testicular germ cell cancer in Ontario by histologic subgroup, 1964-1996.

BACKGROUND: Testicular cancer is rare but is notable because it affects mainly young men. The incidence of this disease has been increasing in developed countries throughout the world for several decades. The authors examined trends in the incidence of testicular germ cell cancer in Ontario for the period 1964-1996 according to the 2 main histologic groups, seminoma and non-seminoma. METHODS: Data on incident cases of testicular germ cell cancer diagnosed in Ontario residents aged 15-59 years between 1964 and 1996 were extracted from the population-based Ontario Cancer Registry. Annual rates of testicular cancer for the 2 histologic groups were analysed by means of log-linear regression to estimate average annual percent change. RESULTS: Between 1964 and 1996 the incidence of testicular germ cell cancer increased by 59.4%, from 4.01 to 6.39 per 100,000. This corresponded to an average annual increase of about 2% for both nonseminoma and seminoma. The relative increase in incidence was greatest in the lowest age group (15-29 years) for both histologic groups, although the data suggest that the incidence of nonseminoma cancer in this age group began to decline in the early 1990s. The increase in incidence appears to be due to a birth cohort effect, with more recent cohorts of men at increased risk. INTERPRETATION: The rise in the incidence of testicular germ cell cancer, not only in Ontario but also in many developed countries, requires investigation. The search for explanatory factors should focus on exposures whose prevalence may have increased over the past few decades and that are common enough to affect population incidence. The similarity of trends for seminoma and nonseminoma cancer suggests that the underlying risk factors are likely the same.

Adolescent↗

PubMed1999

Association of cutaneous malignant melanoma with intermittent exposure to ultraviolet radiation: results of a case-control study in Ontario, Canada.

BACKGROUND: Although solar radiation is well established as a risk factor for melanoma, it is less clear how the pattern and timing of exposure to ultraviolet (UV) radiation might be important. The particular objective of this study was to evaluate the association of melanoma risk with various measures of intermittent and chronic exposures to UV radiation, and to assess how these exposures interact with other risk factors such as skin type. METHODS: Data were analysed from a large case-control study (583 cases, 608 controls) of malignant melanoma, carried out in southern Ontario, Canada. RESULTS: Significant risk increases were identified with several measures of intermittent exposure, including beach vacations in adolescence and in the past 5 years, previous sunburn, and use of sunbeds and sunlamps. Chronic exposure, indicated by days of outdoor activity during adolescence and by occupation in recent adult life, was associated with significantly reduced risk. Subgroup analyses showed: no major risk differences by body site of melanoma; stronger association of lentigo maligna melanoma with intermittent exposure; more pronounced effects of beach vacations and sunburn in younger subjects; and consistently higher risks for intermittent exposures among subjects with skin more susceptible to burning. CONCLUSIONS: The data lend limited support to the hypothesis of increased risk associated with intermittent UV exposure. The findings suggest that future studies should take age at diagnosis, host susceptibility and histological subtype into account.

Adult↗

PubMed1998

Age at puberty and risk of testicular germ cell cancer (Ontario, Canada).

OBJECTIVES: Incidence rates of testicular cancer are increasing among postpubescent men. This suggests that putative exposures may operate early in life and have changed over time. The age at which endocrine activity accelerates (age at puberty) may be such an exposure. This study was undertaken to investigate the relationship between age at puberty and testicular cancer risk. METHODS: A population-based case-control study was conducted in the province of Ontario, Canada which included males, aged 16 to 59 years, diagnosed with testicular germ cell cancer between 1987 and 1989, and age-matched controls. Data were collected on 502 cases, 346 case mothers, 975 controls, and 522 control mothers. Surrogate measures for age at puberty included age at starting to shave, appearance of hair, growth spurt, and voice change. RESULTS: A protective effect of later puberty was evident for all four measures of puberty as reported by both subjects and mothers, and greater protection was conferred when the greatest number of later puberty events were reported. Risk associated with earlier puberty was inconclusive. CONCLUSIONS: As age at puberty is decreasing in the population, the proportion of boys experiencing the protective effect of later puberty may be diminishing. This may help explain the increasing incidence of testicular cancer.

Adolescent↗

PubMed1998

Challenges of developing a cervical screening information system: the Ontario pilot project.

OBJECTIVE: To create a cervical screening information and reporting system in 2 geographic areas of Ontario. DESIGN: A pilot project involving access to, and linkage of, cervical screening-related cytology, colposcopy and histopathology records for women in the study areas, followed by development and production of woman-specific and aggregate reports. SETTING: Hospital cytology and pathology departments, colposcopy clinics, private cytology laboratories, and the provincial cancer agency (Cancer Care Ontario, formerly the Ontario Cancer Treatment and Research Foundation). MAIN OUTCOME MEASURES: Access to required records; data quality (i.e., standardization, completeness, accuracy); quality of record linkage; utility of reports to evaluators, data sources and physicians. RESULTS: The pilot project was not completed because of a number of major challenges, including multiple data sources requiring separate investigation and negotiations for access; variations in reporting terminology and coding; incompatibility or lack of computer systems; incompleteness of identifiers for record linkage; variation in legislation permitting data access and sharing and in its interpretation; and major financial, resource and time requirements. CONCLUSIONS: Although sufficient will and resources can overcome technical obstacles, changes in legislation will be required to overcome other challenges. Strong links with all sectors involved in cervical screening and attention to changes in the health care system are essential.

Colposcopy↗

PubMed1997

Parental occupational exposure and the risk of testicular cancer in Ontario.

The incidence of germ cell testicular cancer is increasing, but its etiology remains largely unknown. Initiation may occur in a parental germ cell. In a case-control study in Ontario, jobs and industries of mothers (before and during pregnancy) and fathers (before pregnancy) of 343 case subjects and 524 control subjects were analyzed. Significantly increased risk was associated with fathers who were wood processors (odds ratio [OR] = 10.46; 95% confidence interval [CI], 1.20 to 91.14), metalworkers (OR = 3.28; 95% CI, 1.03 to 10.52), stationary engineers (OR = 1.05; 95% CI, 1.05 to 11.87), or employees of the food products (OR = 2.79; 95% CI, 1.34 to 5.79), metal products (OR = 5.77, 95% CI, 1.53 to 21.77), or food and beverage services (OR = 4.36; 95% CI, 1.50 to 12.63) industries. There was little evidence of risk associated with maternal employment. Paternal employment before conception in jobs related particularly to metal or food and beverages may be related to testicular cancer risk in sons.

Adolescent↗

PubMed1996

Differences in risk factors for epithelial ovarian cancer by histologic type. Results of a case-control study.

A case-control study of associations between dietary and reproductive factors and cancer of the ovary was conducted during 1989-1992 in metropolitan Toronto and nearby areas of southern Ontario, Canada. In total, 450 women aged 35-79 years with histologically verified new primary epithelial ovarian cancers were interviewed concerning their reproductive history and dietary practices. Over the same time period, 564 randomly selected population controls, frequency-matched to the cases according to three 15-year age groups, were also interviewed. Continuous unconditional logistic regression methods were used for analysis. It was found that childbearing and use of oral contraceptives were associated with significant decreasing trends in the risk of epithelial ovarian cancer of all principal histologic types except mucinous tumors. For each full-term pregnancy, the odds ratio was 0.76 (95% confidence interval (CI) 0.69-0.85) for nonmucinous tumors and 1.03 (95% CI 0.88-1.21) for mucinous tumors; for each year of oral contraceptive use, the odds ratio was 0.89 (95% CI 0.85-0.93) for nonmucinous tumors and 0.98 (95% CI 0.93-1.04) for mucinous tumors (p = 0.00051 and p = 0.0040, respectively, for the difference in odds ratios between mucinous and nonmucinous tumors). Saturated fat intake also appeared to convey greater increased risk for women with mucinous tumors than for women with neoplasms of other histologic types (p = 0.029). Among women with nonmucinous tumors, increasing trends in risk of invasive serous cancer (p = 0.018), and particularly endometrioid cancer (p = 0.0041), were seen with use of noncontraceptive estrogens. Otherwise, borderline-malignant neoplasms seemed to have a similar spectrum of risk factor associations as invasive cancers. On the basis of this study and a number of others, the authors suggest that mucinous ovarian tumors may be etiologically unrelated to other types of epithelial tumors, and thus should be considered separately in studies of ovarian cancer.

Adult↗

PubMed1996

Case-control study of bladder cancer and chlorination by-products in treated water (Ontario, Canada).

Chlorine is by far the most commonly used chemical for the disinfection of water supplies in North America. However, chlorine reacts with organic material in the raw water producing a number of halogenated hydrocarbon by-products. This population-based case-control study in Ontario, Canada examined the relationship between bladder cancer and exposure to chlorination by-products in public water supplies. Residence and water source histories and data from municipal water supplies were used to estimate individual exposure according to water source, chlorination status, and by-product levels (represented by trihalomethane [THM] concentration). Exposures were estimated for the 40-year period prior to the interview, using 696 cases diagnosed with bladder cancer between 1 September 1992 and 1 May 1994 and 1,545 controls with at least 30 years of exposure information. Odds ratios (OR) adjusted for potential confounders were used to estimate relative risk. Those exposed to chlorinated surface water for 35 or more years had an increased risk of bladder cancer compared with those exposed for less than 10 years (OR = 1.41, 95 percent confidence interval [CI] = 1.10-1.81). Those exposed to an estimated THM level > or = 50 micrograms/liter for 35 or more years had 1.63 times the risk of those exposed for less than 10 years (CI = 1.08-2.46). These results indicate that the risk of bladder cancer increases with both duration and concentration of exposure to chlorination by-products, with population attributable risks of about 14 to 16 percent. Chlorination by-products represent a potentially important risk factor for bladder cancer.

Case-Control Studies↗