admission. This proportion could already be greater in some parts of the country and may increase if referrals of cases of self-poisoning increase faster than the facilities for their assessment and management. The provision of social work and psychiatric expertise in casualty departments may be one means of preventing unnecessary medical admissions without risk to the patients. Dr Blake's and Dr Bramble's figures do not demonstrate, however, that any advantage would attach to medical teams taking over assessment from psychiatrists except that, by implication, assessments would be completed sooner by staff working on the ward full time. What the figures actually suggest is that if assessment of overdoses were left to house doctors there would be an increase in admissions to psychiatric units (by 19°U), outpatients (by 5O°'), and referrals to social services (by 140o). So for house doctors to assess overdoses would provide no economy for the psychiatric or social services. The study does not tell us what the consequences would have been for the six patients who the psychiatrists would have admitted but to whom the house doctors would have offered outpatient appointments. E J SALTER

Vitamin D deficiency.

Objective: To determine the ability of measurements of bone density in women to predict later fractures. Design: Meta-analysis of prospective cohort studies published between 1985 and end of 1994 with a baseline measurement of bone density in women and subsequent follow up for fractures. For comparative purposes, we also reviewed case control studies of hip fractures published between 1990 and 1994. Subjects: Eleven separate study populations with about 90000 person years of observation time and over 2000 fractures. Main outcome measures: Relative risk of fracture for a decrease in bone mineral density of one standard deviation below age adjusted mean. Results: All measuring sites had similar predictive abilities (relative risk 1.5 (95% confidence interval 1.4 to 1.6)) for decrease in bone mineral density except for measurement at spine for predicting vertebral fractures (relative risk 2.3 (1.9 to 2.8)) and measurement at hip for hip fractures (2.6 (2.0 to 3.5)). These results are in accordance with results of case-control studies. Predictive ability of decrease in bone mass was roughly similar to (or, for hip or spine measurements, better than) that of a 1 SD increase in blood pressure for stroke and better than a 1 SD increase in serum cholesterol concentration for cardiovascular disease. Conclusions: Measurements of bone mineral density can predict fracture risk but cannot identify individuals who will have a fracture. We do not recommend a programme of screening menopausal women for osteoporosis by measuring bone density. Key messages Measuring bone mineral density has been suggested as a method of identifying individuals at high risk of fracture in a preventive context Our meta-analysis of prospective studies showed that all studies measuring bone density at any site had similar predictive ability for a decrease of 1 SD in bone density except for measurements at hip and spine, which have better predictive ability for fractures in hip and spine respectively Predictive ability of decrease in bone mass was roughly similar to (or, for hip or spine measurements, better than) that of a 1 SD increase in blood pressure for stroke and better than a 1 SD increase in serum cholesterol concentration for cardiovascular disease Although bone mineral density measurements can predict fracture risk, they cannot identify individuals who will have a fracture, and a screening programme for osteoporosis cannot be recommended

Meta-analysis of how well measures of bone mineral density predict occurrence of osteoporotic fractures

Assessment of fracture risk and its application to screening for postmenopausal osteoporos

The criteria required for an effective screening strategy for osteoporosis are largely met in Caucasian women. The disease is common and readily diagnosed by the measurement of bone mineral with single- or dual-energy absorptiometry. Such measurements have high specificity but lower sensitivity, so that the value of the technique is greater for those identified as being at higher risk. Against this background there is little evidence that osteoporosis can usefully be tackled by a public health policy to influence risk factors such as smoking, exercise and nutrition. This suggests that it is appropriate to consider targetting of treatment with agents affecting bone metabolism to susceptible individuals. Since the main benefits of the use of hormone replacement therapy (HRT) are probably on cardiovascular morbidity, the major role for selective screening is to direct non-HRT interventions. An appropriate time to consider screening and intervention is at the menopause, but screening at later ages is also worthy of consideration. Since the cost of screening is low and that of bone-active drugs is high, the selective use of screening techniques will improve the cost-benefit ratio of intervention.

Assessment of fracture risk and its application to screening for postmenopausal osteoporosis: synopsis of a WHO report. WHO Study Group.

Context: Altered vitamin D and calcium homeostasis may play a role in the development of type 2 diabetes mellitus (type 2 DM). Evidence Acquisition and Analyses: MEDLINE review was conducted through January 2007 for observational studies and clinical trials in adults with outcomes related to glucose homeostasis. When data were available to combine, meta-analyses were performed, and summary odds ratios (OR) are presented. Evidence Synthesis: Observational studies show a relatively consistent association between low vitamin D status, calcium or dairy intake, and prevalent type 2 DM or metabolic syndrome [OR (95% confidence interval): type 2 DM prevalence, 0.36 (0.16–0.80) among nonblacks for highest vs. lowest 25-hydroxyvitamin D; metabolic syndrome prevalence, 0.71 (0.57–0.89) for highest vs. lowest dairy intake]. There are also inverse associations with incident type 2 DM or metabolic syndrome [OR (95% confidence interval): type 2 DM incidence, 0.82 (0.72–0.93) for highest vs. lowest combined vitamin D an...

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The Role of Vitamin D and Calcium in Type 2 Diabetes. A Systematic Review and Meta-Analysis

Calcium and osteoporosis

Contrary to frequent claims, vitamin D insufficiency does not generally cause malabsorption of calcium because serum 1,25(OH)(2)D, which is the major determinant of calcium absorption, is maintained by secondary hyperparathyroidism. Nevertheless, because malabsorption of calcium has been described in osteomalacia, there must be a 25(OH)D level below which the serum 1,25(OH)(2)D can no longer be sustained, although it has never been defined. This paper seeks to define it. We examined the records of 3661 patients and found 319 with a serum 25(OH)D < or = 40 nM, in whom calcium absorption, serum calcium, PTH, bone markers, and vitamin D metabolites had been measured. They were grouped according to their serum 25(OH)D into four categories, 0-10, 11-20, 21-30, and 31-40 nM, and differences between the groups were tested by ANOVA. Correlations between the variables were also examined. Serum calcium, 1,25(OH)(2)D, and calcium absorption were significantly decreased and serum PTH and alkaline phosphatase (ALP) and urine hydroxyproline were increased in those with 25(OH)D < or = 10 nM. Serum ALP and urine hydroxyproline were more strongly related, inversely, to calcium absorption than to the vitamin D metabolites. We conclude that vitamin D deficiency does not reduce serum 1,25(OH)(2)D, and therefore calcium absorption, until the serum 25(OH)D falls to approximately 10 nM. At this level, the substrate concentration seems to be insufficient to maintain the level of the dihydroxy metabolite despite secondary hyperparathyroidism. Further studies are needed to see how these changes correlate with the histological changes of osteomalacia.

Vitamin D Metabolites and Calcium Absorption in Severe Vitamin D Deficiency

OBJECTIVE: Because it has been reported that vitamin D, given to mother or infant, can prevent type I diabetes in children, that diabetes is more common in adults with low serum vitamin D and that insulin secretion and action are related to vitamin D levels in healthy young adults we examined the relationship between serum vitamin D metabolites and fasting serum glucose in patients attending our outpatient clinics. DESIGN: Retrospective examination of convenience sample of postmenopausal women attending our osteoporosis clinics. PATIENTS: A total of 753 postmenopausal women attending a university hospital outpatient clinic and not on any treatment known to affect glucose metabolism. MEASUREMENTS: Body weight and height, serum 25-hydroxyvitamin D [25(OH)D], serum 1,25-dihydroxyvitamin D [1,25(OH)2D], serum PTH and fasting serum glucose. RESULTS: On simple correlation fasting serum glucose was a positive function of age (P < 0.05), weight (P < 0.001) and body mass index (BMI) (P < 0.001) and a negative function of serum 25(OH)D (P < 0.001), but it was not significantly related to either serum 1,25(OH)2D, PTH or creatinine. When fasting serum glucose was regressed simultaneously on age, BMI and 25(OH)D, glucose was still an inverse function of 25(OH)D (P = 0.006). CONCLUSIONS: Fasting serum glucose increased as 25(OH)D levels fell throughout the range of serum 25(OH)D measured but the greatest increase was observed in those with 25(OH)D below 40 nmol/l.

Relationship between fasting serum glucose, age, body mass index and serum 25 hydroxyvitamin D in postmenopausal women

Effect of age on calcium absorption in postmenopausal women

It has been known for many years that serum PTH rises with age, and it has been suggested that this rise may contribute to bone loss in postmenopausal women. It has been variously attributed to declining renal function, declining calcium absorption efficiency, and declining serum 25-hydroxyvitamin D [25(OH)D] levels. We studied the effects of age, weight, renal function, radiocalcium absorption, serum ionized calcium, and serum 25(OH)D on serum PTH levels in 918 postmenopausal women attending an osteoporosis center. On simple linear regression, serum PTH was a positive function of age (P = 0.003) and weight (P < 0.001) and an inverse function of serum 25(OH)D (P < 0.001) and serum ionized calcium (P = 0.002). On stepwise regression, serum 25(OH)D was the most significant (negative) determinant of serum PTH, followed in decreasing order of significance by serum ionized calcium (negative) and body weight and age (positive). Serum PTH was not related to radiocalcium absorption. The reciprocal relation between serum PTH and serum 25(OH)D could not be explained by the serum concentration of 1,25-dihydroxyvitamin D, which did not change with age. After adjustment for serum ionized calcium, body weight, and age, the rise in serum PTH appeared to start when serum 25(OH)D fell less than 80 nmol/liter.

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B. E. Christopher Nordin

Papers

Calcium and osteoporosis

Vitamin D Metabolites and Calcium Absorption in Severe Vitamin D Deficiency

Relationship between fasting serum glucose, age, body mass index and serum 25 hydroxyvitamin D in postmenopausal women

Effect of age on calcium absorption in postmenopausal women

The Effects of Age and Other Variables on Serum Parathyroid Hormone in Postmenopausal Women Attending an Osteoporosis Center