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Biomedical subjects

A H Smith

Publications and source records attributed to A H Smith.

At least 109 records · Page 6Linked to original sources
PubMed1988

Cancer case-control studies with other cancers as controls.

Theoretical considerations concerning the use of other cancer patients as controls in cancer case-control studies are reviewed. Selection bias may be a problem in that some other cancers may be caused by the exposure under study biasing the odds ratio towards unity. Such bias is noted to be greatest with low prevalence exposures associated with high attributable risks for other cancers. However, it may be possible to identify selection bias with other cancer controls using census or other general population data. In addition, using other cancers as controls has important advantages with regard to recall and interviewer bias, which may be of unknown magnitude and direction when using general population controls. A further disadvantage of general population controls is that separate selection of decreased controls should usually be made for deceased cases, whereas a mixture of live and deceased controls can be expected when selecting other cancer patients as controls. Since there are also logistical and cost advantages in using other cancer patients as controls, this study design is likely to be used increasingly in the future, particularly in cancer registry settings.

Epidemiologic Methods↗
PubMed1988

Blood pressure and blood lead concentration in bus drivers.

San Francisco bus drivers have an increased prevalence of hypertension. This study examined relationships between blood lead concentration and blood pressure in 342 drivers. The analysis reported in this study was limited to subjects not on treatment for hypertension (n = 288). Systolic and diastolic pressures varied from 102 to 173 mm Hg and from 61 to 105 mm Hg, respectively. The blood lead concentration varied from 2 to 15 micrograms/dL. The relationship between blood pressure and the logarithm of blood lead concentration was examined using multiple regression analysis. Covariates included age, body mass index, sex, race, and caffeine intake. The largest regression coefficient relating systolic blood pressure and blood lead concentration was 1.8 mm Hg/ln (micrograms/dL) [90% C. I., -1.6, 5.3]. The coefficient for diastolic blood pressure was 2.5 mm Hg/ln (micrograms/dL) [90% C. I., 0.1, 4.9]. These findings suggest effects of lead exposure at lower blood lead concentrations than those concentrations that have previously been linked with increases in blood pressure.

Adult↗
PubMed1987

Breast cancer diagnosis under the age of forty years.

The authors report on a multicentric consecutive series of 382 cases of primary breast cancer detected before the age of 40 years. Physical examination (PE) was always performed, whereas other diagnostic tests were performed in selected cases, namely mammography (M) in 334, fine needle aspiration cytology (CYT) in 188 and thermography (TH) in 123 cases. Single tests showed a high rate of false-negative/benign cases (PE, 0.23; M, 0.26; CYT, 0.37 and TH, 0.50), especially when the T1 subgroup was considered (PE, 0.34; M, 0.38; CYT, 0.42 and TH, 0.78). The poor results recorded for TH make its current diagnostic use highly questionable. The policy of extensive biopsy of all "dubious" benign lesions on PE allowed for the detection of 41 of 382 cancers and reduced the PE false-negative/benign rate to 0.12 for the total or 0.15 for T1 cancers, although about 80 unnecessary biopsies for each cancer detected were performed in this way. The association of PE to one or more tests resulted in even lower false-negative rates (0.06 for the total, 0.10 for T1 cancers). The authors criticize the aggressive policy of extensive biopsy recommendation based only on a dubious report on PE alone and stress the opportunity of the routine association of M and CYT to PE, since this combination seems to achieve a higher breast cancer detection rate even in this age group.

Adult↗
PubMed1987

Non-Hodgkin's lymphoma and farming: an expanded case-control study.

A previously published case-control study of agricultural risk factors involved male cases of non-Hodgkin's lymphoma registered under code 202 of the International Classification of Diseases (ICD). This study has been expanded with the inclusion of cases registered under ICD code 200, and additional controls. The expanded study comprises 100 ICD 200 cases and 83 ICD 202 cases registered during the period 1977-81, together with 338 controls selected from other cancer registrations during the same period. The largest relative risk for specific farming types was for orchard workers (odds ratio = 3.7, 90% confidence limits 1.1-12.1). No elevated risks were observed for exposure to farm animals, nor for potential exposure to phenoxy herbicides (odds ratio = 1.0, 90% confidence limits 0.7-1.5), or chlorophenols (odds ratio = 1.4, 90% confidence limits 0.8-2.3). The previous finding of an excess risk associated with fencing work was weakly supported by the expanded study (odds ratio = 1.4, 90% confidence limits 1.0-2.0). However, the previous finding of an excess risk associated with meat works employment was more strongly supported (odds ratio = 1.8, 90% confidence limits 1.2-2.6). One relevant risk factor is 2,4,6-TCP which is used in the treatment of pelts, but the excess risks do not appear to be confined to pelt department workers. An alternative hypothesis is that meat workers may be exposed to oncogenic viruses.

Agricultural Workers' Diseases↗
PubMed1987

A controlled trial of methylene blue in severe depressive illness.

Methylene blue, 15 mg/day, was compared with placebo in treatment of severe depressive illness. The 3-week trial was designed to avoid bias by placebo response and also to avoid observer bias. Improvement in patients receiving methylene blue was significantly greater than in those receiving placebo. Methylene blue at a dose of 15 mg/day appears to be a potent antidepressant, and further clinical evaluation is essential.

Adult↗
PubMed1987

Hormone profiles and psychological symptoms in peri-menopausal women.

Hormone profiles for oestradiol, progesterone, follicle-stimulating hormone, luteinizing hormone, testosterone, androstenedione, prolactin, cortisol, thyroid-stimulating hormone (TSH) and triiodothyronine are presented for 85 peri-menopausal women. All subjects completed the 60-item General Health Questionnaire (GHQ) and 48 were interviewed using a standardized psychiatric interview. Some alterations in endocrine function were detected prior to the cessation of menstrual periods and there were changes in prolactin, cortisol, TSH and triiodothyronine in relation to menopausal status as well as in ovarian steroids and gonadotrophins. In comparison with other subjects, women with menorrhagia had higher circulating levels of oestradiol in the last week of the menstrual cycle and elevated prolactin levels. Women with high scores on the GHQ in the early post-menopausal years had significantly higher circulating levels of oestradiol than other subjects of the same menopausal status. No other significant difference in levels of reproductive hormones between high scorers and low scorers on the GHQ was detected. Women in the late pre-menopausal group who were clinically depressed had significantly higher levels of TSH and triiodothyronine than other subjects. These changes in thyroid function in the late pre-menopausal group may be related to the increase in psychiatric morbidity in the immediately pre-menopausal years reported in previous studies.

Adult↗
PubMed1987

Looking backwards from outcome to exposure to assess cancer latency.

Assessing time relationships in cancer epidemiology involves linking exposure and cancer incidence or mortality on a time scale. The traditional approach is to make some exposure criterion the referent point, such as date of first exposure. However, the time relationships between exposure and cancer may also be usefully explored using the date of diagnosis (or death) as the referent point in time. This has been accomplished to date in industry-based case-control studies by estimating the etiologic fraction among ever exposed cases for years prior to death from cancer, and in the serially additive expected dose (SAED) model by estimating excess case exposure dose for each year prior to cancer death. Each of these measures assesses exposure in time windows (of arbitrary width) prior to cancer death or diagnosis. Both measures are mathematically related (by constants) to a measure of the fraction of excess case exposure dose achieved in each time window, where "excess" means beyond that expected on the basis of non-cases or controls. This particular measure, the retrospective excess exposure fraction (REEF) in time windows, may be valuable in exploring time relationships between exposure and cancer. It is concluded that retrospective measures between cancer occurrence and exposure warrant further attention to maximize the informativeness of cancer epidemiology studies.

Epidemiologic Methods↗
PubMed1987

Infant exposure assessment for breast milk dioxins and furans derived from waste incineration emissions.

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) have been detected in human milk samples obtained in several countries. Possible sources include emissions from incineration of municipal waste in resource recovery facilities. A formula is presented for calculating the infant daily dose of dioxin equivalents from breast milk on the basis of the maternal daily intake. Application of the formula suggests that an infant breast-fed for 12 months would receive around 10% of the cumulative exposure dose per body weight that would be received by an adult with 50 years of exposure. Further analysis indicated that the contribution of dioxin equivalents from breast milk to an infant's body concentration at the end of 12 months of breast feeding would amount to 1.7 times the concentration in the mother. However, dioxin and furan emissions from a source calculated to result in worst-case lifetime cancer risks of the order of 1 in 100,000 are only likely to increase breast milk concentrations by around 1%-10% of the levels that have been detected in several countries. This finding suggests that there are major sources of dioxins and furans other than from municipal solid waste incineration that need to be identified.

Adult↗
PubMed1987

Further studies of vanadium in depressive psychosis.

Three studies are reported. In study 1, vanadium concentration was estimated by neutron activation analysis in hair, whole blood, serum and urine from 13 patients suffering from depressive psychosis and then when on recovery. Vanadium concentration of hair, whole blood and serum decreased significantly with recovery, but there was no significant change in 24-h urinary excretion or in renal clearance of vanadium. In study 2, vanadium concentration was estimated by neutron activation analysis in serum and urine of 31 patients with depressive psychosis and of 27 normal controls. Mean renal clearance of vanadium was significantly lower and mean serum vanadium concentration significantly higher in depressed patients than in controls. Mean 24-h excretion of vanadium did not differ between the two groups. Vanadium excretion did not correlate with urine volume, with serum concentration or with age. In study 3, erythrocyte Na-K ATPase activity and serum vanadium concentrations were estimated in 58 patients. There was a strong negative correlation between the two, supporting the suggestion that changes in tissue vanadium concentration may explain the changes in sodium transport which occur in depressive psychosis.

Adult↗
PubMed1986

De-functioning stomas: a prospective controlled trial comparing loop ileostomy with loop transverse colostomy.

Patients undergoing colorectal surgery who required a defunctioning stoma were randomly allocated to receive either a loop ileostomy (n = 23) or transverse loop colostomy (n = 24). Assessment was made during construction, immediately postoperatively, during the period of outpatient supervision and before and after stoma closure. The ileostomy was associated with significantly less odour than the colostomy (P less than 0.01) and required significantly less appliance changes (P less than 0.05). Furthermore eleven patients (58 per cent) with a colostomy experienced three or more problems with stoma management compared with only three patients (18 per cent) with an ileostomy (P less than 0.05). Wound infection was also significantly more common after closure of the colostomy compared with the ileostomy. Both types of stoma were demonstrated objectively to defunction the distal bowel almost completely. These results indicate that a loop ileostomy is the procedure of first choice when a stoma is needed to defunction the distal colorectum.

Adult↗
PubMed1986

Risk factors in the prevalence of anencephalus and spina bifida in New Zealand.

This paper presents results from an epidemiological study on the 51 anencephalus and 53 spina bifida cases in the 1978 New Zealand birth cohort. Multiple sources were used in the ascertainment, and the prevalence rates were 0.98 and 1.02 per 1,000 total births, respectively. No association was found with the traditional indicators of the effect of environmental factors: maternal age, social class, nuptiality, month of birth, or estimated month of conception. Males comprised 41% of anencephalus and 36% of spina bifida cases; the prevalence was higher in the non-Maori than in the Maori population. New Zealand-born mothers appear to have a much lower risk of spina bifida, but not anencephaly, than those born in England/Scotland. The rate for the latter population was within the range of a number of UK-based studies. As the bloodstock of New Zealand whites has been predominantly derived from the UK population, and as New Zealand is a low prevalence area, this suggests that the higher risk for these women is likely to be attributable to factors present in their birthplace but absent in New Zealand. These findings provide further evidence that the epidemiologic patterns of anencephalus and spina bifida in low-prevalence areas are at variance with those in high-prevalence areas, such as the United Kingdom. They also support the hypothesis that the contrast in rates between high- and low-prevalence areas is a reflection of the impact of environmental factors in high-prevalence areas on the "background" or baseline frequency of anencephalus and spina bifida found in low-prevalence areas.

Adult↗
PubMed1986

Are scintigrams of the spine useful in vertebral osteoporosis?

To determine whether technetium diphosphonate scintigraphy could be used to date vertebral crush fractures, serial scintigrams and radiographs were obtained on two groups of 27 osteoporotic patients. Although radiologically crushed vertebrae were significantly associated with areas of increased isotope uptake on the scintigrams (p less than 0.001), this did not depend on the age of the crush fracture. Some radiologically uncrushed vertebrae, particularly in the lumbar spine, also showed increased isotope uptake.

Adult↗
PubMed1986

Case-control study of multiple myeloma and farming.

A previous case-control study which utilised the occupational information available on the New Zealand Cancer Registry found an increased risk of multiple myeloma in agricultural workers consistent with previous findings in the United States. The findings are now presented for the second phase of the study which involved interviewing 76 cases of multiple myeloma (who had been included in the previous study) together with 315 controls with other types of cancer. The previous finding on an excess of farmers in the case group was confirmed by the interview data (odds ratio = 1.7, 95% confidence limits 1.0-2.9, P = 0.04). There were no significant differences between cases and controls regarding potential exposure to phenoxy herbicides or chlorophenols. There were also no significant differences regarding activities involving potential exposure to other agricultural chemicals, although the odds ratio for fencing work, which may involve exposure to arsenic and sodium pentachlorophenate, was 1.6 (95% confidence limits 0.9-2.7, P = 0.11). The odds ratios were significantly elevated for sheep farming (odds ratio = 1.9, 95% confidence limits 1.0-3.6, P = 0.04) and exposure to beef cattle (odds ratio = 1.7, 95% confidence limits 1.0-2.9, P = 0.05). The odds ratio was also elevated for persons reporting a history of hay fever (odds ratio = 1.9, 95% confidence limits 1.0-3.5, P = 0.05). Overall, these findings suggest that the search for the causes of elevated mortality in farmers from multiple myeloma should be directed to potential causes other than pesticide exposure.

Aged↗
PubMed1986

Non-Hodgkin's lymphoma and exposure to phenoxyherbicides, chlorophenols, fencing work, and meat works employment: a case-control study.

A previous case-control study which used the occupational information available on the New Zealand Cancer Registry found that agricultural workers were at increased risk of developing non-Hodgkin's lymphoma. The findings are now presented for the second phase of the study which entailed interviewing 83 cases of non-Hodgkin's lymphoma registered under code 202 of the International Classification of Diseases together with 168 controls with other types of cancer and 228 general population controls. The findings for the two control groups were similar, and there were no significant differences between cases and controls regarding potential exposure to phenoxy-herbicides (odds ratio = 1.4, 90% confidence limits 0.7-2.5, p = 0.26) or chlorophenols (odds ratio = 1.3, 90% confidence limits 0.6-2.7, p = 0.39). The odds ratio for fencing work, necessitating exposure to several potential risk factors including arsenic and sodium pentachlorophenate was 2.0 (90% confidence limits 1.3-3.0, p = 0.01). The odds ratio for employment in a meat works, necessitating potential exposure to 2, 4, 6-trichlorophenol and zoonotic viruses, was 1.8 (90% confidence limits 1.1-3.1, p = 0.04). There was a significant statistical interaction between the risks associated with these two activities, the odds ratio for involvement in both activities compared with involvement in neither being 5.7 (90% confidence limits 2.3-14.3, p = 0.03).

2,4,5-Trichlorophenoxyacetic Acid↗