Biomedical subjects

V Siskind

Publications and source records attributed to V Siskind.

At least 19 recordsLinked to original sources

PubMed2003

Self-reported difficulty in conceiving as a measure of infertility.

BACKGROUND: This study aimed to explore the meaning and potential use of women's self-reported difficulties in conceiving as a measure of infertility in epidemiological studies, and to compare women's stated reasons for infertility with information in their medical records. METHODS: Data were available from a population-based case-control study of ovarian cancer involving 1638 women. The sensitivity and specificity of women's self-reported infertility were calculated against their estimated fertility status based on detailed reproductive histories. Self-reported reasons for infertility were compared with diagnoses documented in women's medical records. RESULTS: The sensitivity of women's self-reported difficulty in conceiving was 66 and 69% respectively when compared with calendar-derived and self-reported times taken trying to conceive; its specificity was 95%. Forty-one (23%) of the 179 women for whom medical records were available had their self-reported fertility problem confirmed. Self-reported infertility causes could be compared with diagnoses in medical records for only 22 of these women. CONCLUSIONS: Self-reported difficulty conceiving is a useful measure of infertility for quantifying the burden of fertility problems experienced in the community. Validation of reasons for infertility is unlikely to be feasible through examination of medical records. Improved education of the public regarding the availability and success rates of infertility treatments is proposed.

Case-Control Studies↗

PubMed2003

Tuberculosis-related deaths in Queensland, Australia, 1989-1998: characteristics and risk factors.

OBJECTIVE: To review factors associated with TB-related deaths in Queensland, Australia. DESIGN: Review of data for TB patients dying before treatment completion; demographic and clinico-pathological comparison of TB-related deaths with other notified patients after exclusion of losses to follow-up; matched case-control study of co-morbid conditions in patients under 75 years. RESULTS: Of 1003 tuberculosis cases notified between 1989 and 1998, 127 died before completing anti-tuberculosis treatment. Tuberculosis was the main cause of death in 53 cases, a significant contributor in 34 and unrelated in 40, giving a TB-related case fatality rate of 8.7%. Decedents were older on average, except among indigenous Australians (IA); age-adjusted case fatality rates did not vary significantly among ethnic groups. Pulmonary and disseminated TB, coexistent malnutrition, renal disease and liver disease increased the risk of death. HIV infection increased the risk of dying, but was uncommon among Queensland cases. Neither sputum smear positivity nor drug resistance was associated with risk of death. Twenty-five TB-related deaths occurred before diagnosis, with significant overrepresentation of IA. Most had serious co-morbidities and symptomatic pulmonary disease. Seven socially or geographically isolated decedents did not access documented health care for tuberculosis. CONCLUSIONS: Fatality was related to older age, disseminated disease and co-morbidity. Dying undiagnosed from tuberculosis was associated with respiratory co-morbidity and social and geographical isolation, mainly in the aged in low TB risk populations and in IA in remote regions.

Adolescent↗

PubMed2002

Alcohol, tobacco and breast cancer--collaborative reanalysis of individual data from 53 epidemiological studies, including 58,515 women with breast cancer and 95,067 women without the disease.

Alcohol and tobacco consumption are closely correlated and published results on their association with breast cancer have not always allowed adequately for confounding between these exposures. Over 80% of the relevant information worldwide on alcohol and tobacco consumption and breast cancer were collated, checked and analysed centrally. Analyses included 58,515 women with invasive breast cancer and 95,067 controls from 53 studies. Relative risks of breast cancer were estimated, after stratifying by study, age, parity and, where appropriate, women's age when their first child was born and consumption of alcohol and tobacco. The average consumption of alcohol reported by controls from developed countries was 6.0 g per day, i.e. about half a unit/drink of alcohol per day, and was greater in ever-smokers than never-smokers, (8.4 g per day and 5.0 g per day, respectively). Compared with women who reported drinking no alcohol, the relative risk of breast cancer was 1.32 (1.19-1.45, P<0.00001) for an intake of 35-44 g per day alcohol, and 1.46 (1.33-1.61, P<0.00001) for >/=45 g per day alcohol. The relative risk of breast cancer increased by 7.1% (95% CI 5.5-8.7%; P<0.00001) for each additional 10 g per day intake of alcohol, i.e. for each extra unit or drink of alcohol consumed on a daily basis. This increase was the same in ever-smokers and never-smokers (7.1% per 10 g per day, P<0.00001, in each group). By contrast, the relationship between smoking and breast cancer was substantially confounded by the effect of alcohol. When analyses were restricted to 22 255 women with breast cancer and 40 832 controls who reported drinking no alcohol, smoking was not associated with breast cancer (compared to never-smokers, relative risk for ever-smokers=1.03, 95% CI 0.98-1.07, and for current smokers=0.99, 0.92-1.05). The results for alcohol and for tobacco did not vary substantially across studies, study designs, or according to 15 personal characteristics of the women; nor were the findings materially confounded by any of these factors. If the observed relationship for alcohol is causal, these results suggest that about 4% of the breast cancers in developed countries are attributable to alcohol. In developing countries, where alcohol consumption among controls averaged only 0.4 g per day, alcohol would have a negligible effect on the incidence of breast cancer. In conclusion, smoking has little or no independent effect on the risk of developing breast cancer; the effect of alcohol on breast cancer needs to be interpreted in the context of its beneficial effects, in moderation, on cardiovascular disease and its harmful effects on cirrhosis and cancers of the mouth, larynx, oesophagus and liver.

Adult↗

PubMed2001

Reproduction-related risk factors for mucinous and nonmucinous epithelial ovarian cancer.

The proposition that mucinous ovarian cancer has an etiology distinct from that of other histologic types has been evaluated using data from a population-based case-control study of epithelial ovarian cancer conducted in 1990--1993 among Australian women aged 18--79 years. The protective effects of parity and oral contraceptive use were greater in nonmucinous than in mucinous ovarian tumors. However, these differences appeared to be driven largely by the effect of ovulatory life, which was positively associated with nonmucinous tumors only. An association with family history of breast and/or ovarian cancer also appeared to be restricted to nonmucinous cancers. These results lend support to the hypothesis that mucinous and nonmucinous ovarian tumors develop via different causal mechanisms.

Adolescent↗

PubMed2001

Cigarette smoking and risk of epithelial ovarian cancer (Australia).

OBJECTIVES: We studied the association between cigarette smoking and ovarian cancer in a population-based case control study. METHODS: A total of 794 women with histologically confirmed epithelial ovarian cancer who were aged 18-79 years and resident in one of three Australian states were interviewed, together with 855 controls aged 18-79 years selected at random from the electoral roll from the same states. Information was obtained about cigarette smoking and other factors including age, parity, oral contraceptive use, and reproductive factors. We estimated the relative risk of ovarian cancer associated with cigarette smoking, accounting for histologic type, using multivariable logistic regression to adjust for confounding factors. RESULTS: Women who had ever smoked cigarettes were more likely to develop ovarian cancer than women who had never smoked (adjusted odds ratio (OR) = 1.5; 95% confidence interval (CI) = 1.2-1.9). Risk was greater for ovarian cancers of borderline malignancy (OR = 2.4; 95% CI = 1.4-4.1) than for invasive tumors (OR = 1.7; 95% CI = 1.2-2.4) and the histologic subtype most strongly associated overall was the mucinous subtype among both current smokers (OR = 3.2; 95% CI = 1.8-5.7) and past smokers (OR = 2.3; 95% CI = 1.3-3.9). CONCLUSIONS: These data extend recent findings and suggest that cigarette smoking is a risk factor for ovarian cancer, especially mucinous and borderline mucinous types. From a public health viewpoint, this is one of the few reports of a potentially avoidable risk factor for ovarian cancer.

Adenocarcinoma, Mucinous↗

PubMed2001

Patient and health care system delays in Queensland tuberculosis patients, 1985-1998.

SETTING: Queensland tuberculosis (TB) control centre QTCC). OBJECTIVE: To investigate patient and health care system delays in the diagnosis of active TB in Queensland. DESIGN: Analysis of data extracted from the QTCC database and review of charts. Symptomatic patients with bacteriologically or histologically proven TB were considered as a total group and a pulmonary smear-positive (PSP) group. RESULTS: The median patient delays were 29 days (total group) and 30 days (PSP group). The median health care system delays were 22 days (total group) and 11 days (PSP group). There were significant trends towards increasing health care system delays with increasing age and longer residency of migrants in Australia. Health care system delays were significantly longer for females and those aged over 45. Migrants from countries of high TB incidence and indigenous Australians had shorter health care system delays compared to non-indigenous Australians. Common reasons for diagnostic delays of more than 90 days were failure to perform appropriate investigations and misdiagnosis of chest X-rays. CONCLUSION: Physicians need to consider including TB in the differential diagnosis in older age groups and migrants with longer residency in Australia. There should be a low threshold for obtaining chest X-rays and sputum samples in patients with persistent cough.

Adolescent↗

PubMed2000

Estimating risks for matching factors in case-control studies.

Matching for factors such as age and sex is a convenient method for minimizing confounding in case-control studies, but it does not allow inferences about the effects of the matching factors unless case ascertainment is virtually complete and the distribution of the matching factors in the source population is known. When this is so, the effect of a particular factor can be estimated by comparing the population distribution of that factor with what is observed in the case series. Such a comparison, however, may itself be confounded by other factors that are related to both the matching factors and the disease under investigation. This article proposes a method for evaluating matching factors as risk factors, which uses information on the distribution of potential confounders in the reference series and exposure relative risk estimates to adjust the person-time proportionality constant in a Poisson regression model. The method is particularly suited to data sets in which many of the elementary matching strata contain few or no cases and/or controls. It makes use of standard analytic procedures, but requires the estimation of an additional variance-covariance component for the estimated Poisson regression coefficients. Further factors that may confound the relationship between exposure and disease are easily accommodated. The method is demonstrated in two examples: a matched case-control study of drugs in relation to the rare blood dyscrasia, agranulocytosis, that was conducted in Europe and Israel, and a case-control study of ovarian cancer in Australia.

Adolescent↗

PubMed2000

Beyond ovulation: oral contraceptives and epithelial ovarian cancer.

In a case-control study in three Australian states that included 794 women with epithelial ovarian cancer and 853 community controls for whom we had adequate contraceptive and reproductive histories, we examined the effects of oral contraceptive use after controlling for estimated number of ovulatory cycles. Other covariates included in the multiple logistic regression analysis were parity, smoking, and history of pelvic surgery. The protective effect of duration of oral contraceptive use appeared to be multiplicative, with a 7% decrease in relative risk per year [95% confidence interval (CI) = 4-9%], persisting beyond 15 years of exposure. Use for up to 1 year may have a greater effect than predicted (odds ratio = 0.57; 95% CI = 0.40-0.82), whereas use before the first pregnancy may be additionally beneficial (odds ratio = 0.95; 95% CI = 0.87-1.03, adjusted for overall duration of use). Better control for ovulatory life might attenuate these estimates somewhat. There was little evidence of waning protection with time since last exposure or of extra benefit with early commencement of oral contraceptive use. We found no convincing evidence of effect modification in any factor examined or differences in effect among the three main histologic cancer types or between borderline and malignant tumors. Oral contraceptives may act by both suppressing ovulation and altering the tumor-promoting milieu.

Adult↗

PubMed1999

Hormone replacement therapy and risk of epithelial ovarian cancer.

It has been suggested that oestrogen replacement therapy is associated with risk of epithelial ovarian cancer of the endometrioid type. Using data from an Australian population-based case-control study, the relation between unopposed oestrogen replacement therapy and epithelial ovarian cancer, both overall and according to histological type, was examined. A total of 793 eligible incident cases of epithelial ovarian cancer diagnosed from 1990 to 1993 among women living in Queensland, New South Wales and Victoria were identified. These were compared with 855 eligible female controls selected at random from the electoral roll, stratified by age and geographic region. Trained interviewers administered standard questionnaires to obtain detailed reproductive and contraceptive histories, as well as details about hormone replacement therapy and pelvic operations. No clear associations were observed between use of hormone replacement therapy overall and risk of ovarian cancer. Unopposed oestrogen replacement therapy was, however, associated with a significant increase in risk of endometrioid or clear cell epithelial ovarian tumours (odds ratio (OR) 2.56; 95% confidence interval (CI) 1.32-4.94). In addition, the risk associated with oestrogen replacement therapy was much larger in women with an intact genital tract (OR 3.00; 95% CI 1.54-5.85) than in those with a history of either hysterectomy or tubal ligation. Post-menopausal oestrogen replacement therapy may, therefore, be a risk factor associated with endometrioid and clear cell tumours in particular. Additionally, the risk may be increased predominantly in women with an intact genital tract. These associations could reflect a possible role of endometriosis in the development of endometrioid or clear cell ovarian tumours.

Adenocarcinoma↗

PubMed1997

Tubal sterilisation, hysterectomy and decreased risk of ovarian cancer. Survey of Women's Health Study Group.

We have examined the effect of tubal sterilisation and hysterectomy on risk of ovarian cancer in a large case-control study in eastern Australia involving 824 women aged 18-79 years, diagnosed with epithelial ovarian cancer between 1990 and 1993, and 855 controls randomly selected from the electoral roll. Relative risks for ovarian cancer were estimated using multiple categorical regression to adjust for age, parity, oral contraceptive use and other risk factors. Tubal sterilisation was associated with a 39% reduction in risk of ovarian cancer (RR 0.61, 95% CI 0.46-0.85) and hysterectomy with a 36% reduction (RR 0.64, 95% CI 0.48-0.85). Risk remained low 25 years after surgery and was reduced irrespective of sterilisation technique, and estimates were similar among various types of epithelial ovarian cancer. The greatest reduction (74%) was observed among women with primary peritoneal tumours. Pelvic infection and use of vaginal sprays or contraceptive foams were not related to ovarian cancer, while use of talc in the perineal region slightly but significantly increased risk among women with patent fallopian tubes. Reportedly heavy or painful menses, perhaps associated with retrograde flow, were associated with ovarian cancer, and reduction in risk of disease after hysterectomy was greatest among women who had heavy periods. Our findings support the theory that contaminants from the vagina, such as talc, and from the uterus, such as endometrium, gain access to the peritoneal cavity through patent fallopian tubes and may enhance the malignant transformation of ovarian surface epithelium. Surgical tubal occlusion may reduce the risk of ovarian cancer by preventing the access of such agents.

Adolescent↗

PubMed1997

The time factor in mortality: weather associations in a subtropical environment.

Mortality rates for a decade in Brisbane are analysed for dependence upon atmospheric factors. Time filters are applied to both the dependent and independent variables, and several models are developed to enable prediction, especially for weekly intervals. Statistically, deaths are observed to increase with colder and less humid weather with winds from a westerly, direction. Overall, taking account of both synoptic and seasonal influences, > 90% of cumulative deviations from mean death rates are explained. Some differences are also noted in the association of death with the weather between sexes, age groups and causes of death.

Adolescent↗

PubMed1997

Breastfeeding, menopause, and epithelial ovarian cancer.

No previous study has examined the modifying effect of menopausal status on the association between lactation and ovarian cancer risk. We recruited 824 epithelial ovarian cancer cases and 855 community controls in three Australian states, collecting reproductive and lactation histories by means of a contraceptive calendar and pregnancy and breastfeeding record. We report results in women with at least one liveborn infant for unsupplemented breastfeeding, in line with a biological model linking suppression of ovulation to reduction in ovarian cancer risk. We derived odds ratios from multiple logistic regression models including number of liveborn children, age, age at first or last birth, and other potential confounders, overall and by menopausal status. Estimates of relative risk of ovarian cancer per month of full lactation were 0.99 [95% confidence interval (CI) = 0.97-1.00] overall and 1.00 (95% CI = 0.99-1.01) and 0.98 (95% CI = 0.95-1.01) among post- and premenopausal women, respectively. We tailored a lactation variable to the incessant ovulation hypothesis by progressively discounting breastfeeding the longer after birth it occurred, finding odds ratios similar to those for the unmodified duration variable. We found no association of note among postmenopausal women. Breastfeeding seems to be somewhat protective against ovarian cancer, but only before menopause.

Adult↗

PubMed1997

Validity of self-reported hysterectomy and tubal sterilisation. The Survey of Women's Health Study Group.

Both hysterectomy and tubal sterilisation offer significant protection from ovarian cancer, and the risk of cardiovascular disease in women is lowered after hysterectomy. Since little is known about the accuracy of women's self-reports of these procedures, we assessed their reliability and validity using data obtained in a case-control study of ovarian cancer. There was 100 per cent repeatability for both positive and negative histories of hysterectomy and tubal sterilisation among a small sample of women on reinterview. Verification of surgery was sought against surgeons' or medical records, or if these were unavailable, from randomly selected current general practitioners for 51 cases and 155 controls reporting a hysterectomy and 73 cases and 137 controls reporting a tubal sterilisation. Validation rate for self-reported hysterectomy against medical reports (32 cases, 96 controls) was 96 per cent (95 per cent confidence interval (CI) 91 to 99) and for tubal sterilisation (32 cases, 77 controls) it was 88 per cent (CI 81 to 93), which is likely to be an underestimate. Although findings are based on small numbers of women for whom medical reports could be ascertained, they are consistent with other findings that suggest women have good recall of past histories of hysterectomy and tubal sterilisation; this allows long-term effects of these procedures to be studied with reasonable accuracy from self-reports.

Adolescent↗

PubMed1997

Ultraviolet radiation, melanocytic naevi and their dose-response relationship.

Melanocytic naevi on the face and neck of 110 Brisbane secondary school students aged 16-17 years were mapped according to specified regions to investigate the dose-response relationship between ultraviolet (UV) radiation and melanocytic naevi. Highest naevus density occurred in regions receiving a mean UV dose of 0.2-0.4 relative to the vertex while densities were low in minimally and maximally exposed regions. This pattern of naevus distribution was unaffected by sex or phenotypic features such as skin colour or degree of freckling. These findings suggest that there is a narrow dose range over which UV radiation can effectively promote the proliferation of melanocytes. A comparison of the regional distribution of naevi on the face and neck with that of solar keratoses appearing over 1 year on the heads of residents of a neighbouring town has shown them to differ significantly. This study may shed some light on the unknown, yet expectedly complex, relation of UV radiation to melanocytic naevi.

Adolescent↗

PubMed1996

A population-based study of cancer risk in twins: relationships to birth order and sexes of the twin pair.

One thousand and sixty-three twins with cancer whose co-twin was born alive were identified among patients born since September 1939 with cancers incident in England and Wales during 1971-1984 at childhood and young adult ages. Site-specific risks of cancer were analysed in relation to birth order within the twinship and sexes of the twin pair, using adjusted national birth data to give control distributions of these variables. Risk of leukaemia was increased in first-born twins, risk of testicular cancer was increased in second-born twins with female co-twins but decreased in second-born twins with male co-twins and lung cancer risk was increased in first-born twins with same-sex co-twins. Cutaneous melanoma risk was increased in persons with opposite-sex co-twins, nervous system cancer risk was increased in females with opposite-sex co-twins and Hodgkin's disease risk was increased in persons with same-sex co-twins. For most of the findings, no previous comparable analyses are available, so interpretation of the results must be provisional until the analyses can be repeated on other data. The result for leukaemia would accord with previous suggestions that leukaemia may be of prenatal origin and may sometimes lead to intrauterine death. The Hodgkin's disease result would fit with theories of an infectious aetiology, and this view is strengthened by reanalysis of previous data on paralytic poliomyelitis in twins, which show a pattern similar to that for the Hodgkin's disease patients. Cancer risk in relation to birth order and sex of twins can give novel, objective data relating to prenatal and infectious disease aetiology of cancers.

Adult↗

PubMed1996

Confidence intervals for the excess risk in case-control studies.

Kaufman et al. compute the 'excess risk' of a disease in the presence of an exposure as the product of the incidence rate of the disease in the source population, the complement of the aetiologic fraction and the relative risk minus one. Methods for calculating confidence intervals for this quantity are derived when (as in case-control studies) the relative risk is estimated by the odds ratio, firstly from multiple logistic regression analysis and secondly without adjustment for covariates. For the latter an innovative approach based on confidence bounds for the two exposure parameters is suggested. The performance of these systems of confidence intervals is assessed by simulation for the former and by exact enumeration of the distributions involved in the latter. Illustrative examples from a study of agranulocytosis and indomethacin are presented.

Age Distribution↗

PubMed1996

The risk of skin cancer in renal transplant recipients in Queensland, Australia. A follow-up study.

A long-term retrospective follow-up study was performed to evaluate the risk of skin cancer in 1098 renal transplant recipients in Queensland, Australia. In a subgroup, we also assessed the influence of immunosuppressive therapy on the risk of developing skin cancer: cyclosporine alone or in combination with prednisolone; azathioprine alone or in combination with prednisolone; or the combination of cyclosporine and azathioprine with or without prednisolone. The cumulative incidence of developing skin cancer, calculated by life table analysis, increased progressively from 7% after 1 year of immunosuppression to 45% after 11 years and to 70% after 20 years of immunosuppression. Multivariate analysis in a subgroup comparing the risk of developing skin cancer in patients on either long-term cyclosporine or azathioprine (each with or without prednisolone) and in patients on the combination of cyclosporine and azathioprine (with or with- out prednisolone) showed no differences between the groups. We conclude that it is likely that the increased risk of skin cancer associated with immunosuppression is independent of the agent(s) used and is a result of the immunosuppression per se.

Adolescent↗

PubMed1996

Does license disqualification reduce reoffence rates?

A review was conducted of the subsequent driving records of over 25,000 Queensland drivers cited for a drink driving offence in 1988 who received at least one subsequent license restriction. The interval of follow-up was at least 3 years, average 3.9 years. Periods of driving disqualification were identified and, for each driver, the total amount of time during restricted and unrestricted driving was computed; the numbers of events, i.e. crashes and traffic offences, recorded during these periods were counted. Rates under disqualification and during legal driving, expressed per thousand person-years were derived by dividing total numbers of events by total time during which they could occur. Three categories of traffic violation were considered: drink driving offences; traffic offences unassociated with drink driving, and any offence involving driving. Since only 12% of the offenders and 9% of the reoffenders were female, detailed analyses are presented for men only; results for women were little different. Statistical inference assumed a Poisson model for crashes and a negative binomial model for offences, and analyses were performed after stratification by number of drink driving offences. Calculated rates during periods of disqualification were about one third of the rates during legal driving for crashes and all three categories of traffic offence, ranging from 25% in the case of unassociated offences to 35% for any driving offence. There were differences, some statistically significant, by age and between metropolitan, provincial city and rural regions of the State, but most were relatively minor. Drivers were apprehended more frequently earlier in the disqualification period than later. It is impossible from these data to distinguish between reduced driving levels and more cautious traffic behaviour during periods of license restriction. It is nonetheless clear that while such penalties are in operation, they substantially reduce the negative impact of convicted drink-drivers on the road. Unfortunately the data do not permit one to say whether or for how long the effect persists.

Accidents, Traffic↗