The rational for a mid-scala electrode array

Today increasing numbers of cochlear implant candidates have residual hearing that can be aided and hence is worth trying to preserve. This means that surgical technique and electrode array design must be adapted to minimize trauma. Wide opening of the round window is often preferred to reduce drill related trauma and to avoid pressure spikes during electrode array insertion. A recent meta-analysis suggested that there is no significant correlation between hearing preservation and either insertion depth or scala position. However, a slow insertion speed of at least 30seconds was associated with better hearing preservation. An electrode design is proposed that targets the middle of the scala tympani. This minimizes frictional forces from either lateral or medial wall during insertion and imposes less static pressure on cochlear structures following insertion. The flexibility to insert via the round window requires a 0.7-mm maximum dimension at the proximal end of the array. Micro-anatomical analysis by micro-CT indicated that a 420-degree insertion depth was optimal between cochlear coverage and available space within the scala tympani. Physical measurements showed that mean insertion forces remained below 10mN during insertion. A series of 20 human temporal bone insertions found a mean insertion depth of 400 degrees with no scala dislocations. Six clinical series, in total 94 cases, found postoperative hearing in 81% of cases with a mean loss of 12dB compared to preoperative levels. Speech understanding out to one year post-fitting trended better for a mid-scala design group than for a straight electrode array group; although the differences were not statistically significant. A mid-scala array design appears able to be inserted with minimal trauma, to return a predictable insertion depth across various sizes of cochleae and to support reasonable levels of speech understanding without relying on residual hearing.

The Kety-Schmidt technique for quantitative perfusion and oxygen metabolism measurements in the MR imaging environment

SUMMARY

The Kety-Schmidt technique provides quantitative measurement of whole-brain CBF. CBF is measured as the area between the arterial and venous washout curves of a diffusible tracer. Oxygen extraction and metabolism may be calculated from arterial and venous samples. In this report, we present a method for performing these measurements in an MR imaging environment. This technique could be useful for validation of MR imaging methods of hemodynamic and metabolic measurements in humans.

Is there a 'Scottish effect' for mortality? Prospective observational study of census linkage studies

BACKGROUND

Scotland's mortality rate is higher than England and Wales' and this difference cannot be explained by differences in area-level socio-economic deprivation. However, studies of this 'Scottish effect' have not adjusted for individual-level measures of socio-economic position nor accounted for country of birth; important as Scottish born living in England and Wales also have high mortality risk.

METHODS

Data sets (1991-2001 and 2001-2007) were obtained from the Scottish Longitudinal Study and the Office for National Statistics England and Wales Longitudinal Study that both link census records to subsequent mortality. Analysis was limited to those aged 35-74 at baseline with people followed to emigration, death or end of follow-up.

RESULTS

Those born in Scotland living in either England and Wales or Scotland had a higher mortality rate than the English born living in England and Wales that was not fully attenuated by adjustment for car access and housing tenure.

CONCLUSION

Adjusting for household-level differences in socio-economic deprivation does not fully explain the Scottish excess mortality that is seen for those born in Scotland whether living in England and Wales or Scotland. Taking a life course approach may reveal the cause of the 'Scottish effect'.

Absence of microorganisms in crustacean digestive tracts

Two marine and one terrestrial wood-boring isopod species and one wood-inhabiting amphipod species maintain a digestive tract free of microorganisms. Digestive tracts examined in toto with the scanning electron microscope were devoid of microorganisms. In contrast, the outer exoskeleton surfaces of these crustaceans support a dense bacterialflora. Observations of the hindgut of termites revealed a diverse gut microflora as expected.

The Scottish excess in mortality compared to the English and Welsh. Is it a country of residence or country of birth excess?

Scotland has a higher mortality rate than England and Wales, which is only partially explained by differences in socio-economic deprivation. Within Scotland those born in England and Wales have a lower mortality rate than the Scottish born. Within England and Wales, Scottish born immigrants have a higher mortality rate than those born in England and Wales. These results raise the question of whether the greater Scottish mortality is a country of birth rather than a country of residence excess. Our analysis, around the 2001 Census, suggests that country of birth is more important than country of residence, indicating that early life factors may be important for the Scottish excess.

Social mobility: evidence that it can widen health inequalities

Numerous studies consider the role of social, or occupational, mobility on health inequalities. A common conclusion is that social mobility constrains, rather than widens, social class health inequalities. It is argued that such 'gradient constraint' occurs because movers into higher social classes tend to have poorer health than those they join, while movers into lower social classes tend to have better health than those they join. This has led to the suggestion that increasing social mobility may be an effective policy to reduce health inequalities. However, this raises a paradox as many studies also show that health inequalities are widening. We compare class mobility and deprivation mobility between 1971 and 1991 with health in 1991 in England and Wales. In both cases, the health in 1991 of the 'mobile' tended to fall between that of those they left and those they joined. In comparison to the socially stable, the gradient was thus constrained. However, comparing the health in 1991 of everyone by their class/deprivation position in 1991 and 1971, the overall social class health gradient was little different, while the deprivation health gap was considerably wider in 1991. These results show that a reduction in inequalities is not a necessary consequence if the health of 'mobile' people falls between that of those they left and those they joined and this is particularly the case for deprivation mobility.

Does population mixing measure infectious exposure in children at the community level?

Epidemiological studies focusing on the etiology of childhood chronic diseases have used population mixing as a proxy for the level of infection circulating in a community. We compared different measures of population mixing (based on residential migration and commuting) and other demographic variables, derived from the United Kingdom Census, with hospital inpatient data on infections from two Government Office Regions in England (Eastern and the West Midlands) to inform the development of an infectious disease proxy for future epidemiological studies. The association between rates of infection and the population mixing measures was assessed, using incidence rate ratios across census areas, from negative binomial regression. Commuting distance demonstrated the most consistent association with admissions for infections across the two regions; areas with a higher median distance travelled by commuters leaving the area having a lower rate of hospital admissions for infections. Deprived areas and densely populated areas had a raised rate of admissions for infections. Assuming hospital admissions are a reliable indicator of common infection rates, the results from this study suggest that commuting distance is a consistent measure of population mixing in relation to infectious disease and deprivation and population density are reliable demographic proxies for infectious exposure. Areas that exhibit high levels of population mixing do not necessarily possess raised rates of hospital admissions for infectious disease.

Moving and union dissolution

This paper examines the effect of migration and residential mobility on union dissolution among married and cohabiting couples. Moving is a stressful life event, and a large, multidisciplinary literature has shown that family migration often benefits one partner (usually the man) more than the other Even so, no study to date has examined the possible impact of within-nation geographical mobility on union dissolution. We base our longitudinal analysis on retrospective event-history data from Austria. Our results show that couples who move frequently have a significantly higher risk of union dissolution, and we suggest a variety of mechanisms that may explain this.

Locality deprivation and Type 2 diabetes incidence: A local test of relative inequalities

There is increasing evidence that the socio-spatial context of the local area in which one lives can have an effect on health, but teasing out contextual influences is not a simple task. We examine whether the incidence of Type 2 diabetes in small areas in Tayside, Scotland is associated with deprivation in neighbouring areas, controlling for the deprivation of the area itself. As such, this is a genuinely 'contextual' variable situating each small area in the context of surrounding places. We test two opposing hypotheses. First, a 'psycho-social' hypothesis might suggest that negative social comparisons made by individuals in relation to those who surround them could lead to chronic low-level stress via psycho-social pathways, the physiological effects of which could promote diabetes. Thus, we would expect people living in deprived areas surrounded by less deprived areas to have an increased risk of diabetes, compared to those living in similarly deprived areas that are surrounded by equally or more deprived areas. Alternatively, a neo-materialist approach might suggest that the social, cultural and environmental resources in the surrounding environment will influence circumstances in a particular area of interest. Poorer areas surrounded by less deprived areas would benefit from the better resources in the wider locality, while less deprived areas surrounded by poorer areas may be hampered by the poorer resources available nearby. We refer to this as the 'pull-up/pull-down' hypothesis. Our results show that, as expected, area deprivation is positively related to diabetes incidence (p<0.001), whilst deprivation inequality between areas and their neighbours is negatively related (p=0.006). Type 2 diabetes is more common in deprived areas, but lower in deprived areas that are surrounded by relatively less deprived areas. On the other hand, less deprived areas that are surrounded by relatively more deprived areas have higher diabetes incidence than would be expected from the deprivation of the area alone. Our model results are consistent with a pull-up/pull-down model and lend no support to a 'psycho-social' interpretation at this local scale of analysis.

Does young adult suicide cluster geographically in Scotland?

BACKGROUND

Suicide rose dramatically among young adults in Scotland between 1980-1982 and 1999-2001, especially among those living in deprived areas.

OBJECTIVE

To determine whether there are statistically significant geographical clusters of suicide and undetermined deaths among those aged 15 to 44 years in Scotland, and whether these persist through time.

METHODS

Deaths from suicide and undetermined causes by young adults in Scotland for three periods-1980 to 1982, 1990 to 1992, and 1999 to 2001-were aggregated into 10,058 small areas for Scotland. Tests for significant (p<0.05) geographical clustering of suicide were carried out for each period separately. Methods of suicide inside the identified clusters were compared with those in the rest of Scotland.

RESULTS

A significant geographical cluster of suicide among young adults was identified in east Glasgow in all three time periods (involving 92, 159, and 245 cases). Compared with the rest of Scotland, significantly more deaths in these clusters were caused by poisoning from liquids or solids over the entire period, but this was not the case in the most recent period (1999 to 2001). All three clusters could be explained by the concentration of socioeconomic deprivation in this part of Scotland.

CONCLUSIONS

One interpretation of this large, persistent, and statistically significant cluster of suicides among young adults in east Glasgow is that suicide is geographically contagious, but the present results suggest that it is explained by the concentration of deprivation in this area. Suicide prevention strategies targeting at-risk populations living in east Glasgow are necessary to reduce the suicide burden in Scotland.

Does health-selective migration following diagnosis strengthen the relationship between Type 2 diabetes and deprivation?

Geographical health inequalities have been demonstrated for Type 2 diabetes in many developed countries, with poorer areas tending to have higher rates than wealthier areas. Previous studies have considered diabetes prevalence, relying on cross-sectional data collected from registers or hospital admissions records. However, the environment that had most influence on the development of a person's diabetes may not have been the same environment in which they are identified in a prevalence study. We therefore investigate whether health selective migration confounds the relationship between diabetes and deprivation by following a cohort of Type 2 diabetics from diagnosis until the end of the study, 8-18 years later. Our results demonstrate, first, that there is a significant relationship between material deprivation and diabetes incidence. Secondly, Type 2 diabetics in Tayside, Scotland have become more concentrated in relatively more deprived areas over time, strengthening the relationship between diabetes and material deprivation. Thirdly, and perhaps unexpectedly, this strengthening effect results primarily from selective immobility, rather than selective migration. We conclude that care should be taken when evaluating the relationship between diabetes and deprivation in cross-sectional studies.

Smoking compromises cause-specific survival in patients with operable colorectal cancer

AIMS

To assess whether active smoking compromises survival in patients with colorectal cancer.

MATERIALS AND METHODS

We studied a regionally based cohort of 284 consecutive patients referred to the Tayside Cancer Centre for consideration of adjuvant treatment after curative surgery for colorectal cancer.

RESULTS

Cause-specific survival was significantly worse (P = 0.0015) in patients who were actively smoking at the time of their first post-operative visit. The absolute difference in 5-year cause-specific survival (active smokers vs the rest) was 21%. In adjusted multi-variate analysis of patients after pathologically complete (R0) resection, the hazard ratio was 2.55 (95% confidence interval 1.40-4.64) in active smokers compared with non-smokers. T stage, number of positive nodes and co-morbidity score were also of independent prognostic influence.

CONCLUSIONS

Persistent smoking was, in this small series, an important and independent predictor of cancer-related death after surgery for cancer of the large bowel. Because smoking and deprivation are related, some of the adverse effects of deprivation upon survival in this group of patients may be explained by smoking behaviour.

Shrinking areas and mortality: an artefact of deprivation effects?

There is evidence that mortality rates are highest in areas that are experiencing population decline, and researchers have recommended that this should be accounted for in health resource allocation. This research finds a significant negative association between population change and mortality for small areas in Scotland, which remains when low social class is accounted for. However, this relation disappears when the area deprivation is accounted for. It is suggested that it is more important to account for deprivation than population change in health resource allocation.

Spatial clustering of amyotrophic lateral sclerosis in Finland at place of birth and place of death

Previous evidence for spatial clustering of amyotrophic lateral sclerosis is inconclusive. Studies that have identified apparent clusters have often been based on a small number of cases, which means the results may have occurred by chance processes. Also, most studies have used the geographic location at the time of death as the basis for cluster detection, rather than exploring clusters at other points in the life cycle. In this study, the authors examine 1,000 cases of amyotrophic lateral sclerosis distributed throughout Finland who died between June 1985 and December 1995. Using a spatial-scan statistic, the authors examine whether there are significant clusters of the disease at both time of birth and time of death. Two significant, neighboring clusters were identified in southeast and south-central Finland at the time of death. A single significant cluster was identified in southeast Finland at the time of birth, closely matching one of the clusters identified at the time of death. These results are based on a large sample of cases, and they provide convincing evidence of spatial clustering of this condition. The results demonstrate also that, if the cluster analysis is conducted at different stages of the cases' life cycle, different conclusions about where potential risk factors may exist might result.

Do area-level population change, deprivation and variations in deprivation affect individual-level self-reported limiting long-term illness?

A previous study showed that variations in deprivation within small localities in England and Wales influenced the rates of self-reported limiting long-term illness, controlling for overall levels of deprivation. These results suggest that while morbidity is related to overall levels of material deprivation, the distribution of resources within small areas have a significant effect on health outcomes. However, it is possible that these area effects become redundant once individual-level characteristics are accounted for. This analysis examines whether area-level deprivation and variations in deprivation are significant indicators of individual-level limiting long-term illness, once individual characteristics have been accounted for.

Hypoglycemia. Pathophysiology and treatment

Hypoglycemia is a common consequence of many diabetes treatments. As is true for many therapies for diseases with major pathologic consequences, the benefits and risks of treatment must be balanced. In intensified diabetes management, hypoglycemia is not an insurmountable problem but is unfortunately inevitable using the methods of glucose control currently available. Patients with type 1 diabetes seem to be at greater risk than patients with type 2 disease. The health care team must strive to help the patient maintain normoglycemia. The results of the DCCT and the United Kingdom Prospective Diabetes Study prove that near normoglycemia is clearly in the patient's best interest. Patient education has become focused on minimizing hyperglycemia; counseling on the dangers of hypoglycemia has not been given the same stature. Emphasis must be placed on minimizing even minor subclinical hypoglycemia because it will contribute to a vicious cycle of hypoglycemia begetting hypoglycemia.

The effect on morbidity of variability in deprivation and population stability in England and Wales: an investigation at small-area level

We seek to determine whether variability in deprivation at small area level, and population stability, influence standardised morbidity ratios in England and Wales. A regression analysis was conducted with data from the 1991 British Census, in order to explain variation in morbidity. Both an area deprivation score (for electoral wards) and the within-area variability of deprivation scores were examined as possible determinants of morbidity (self-reported, limiting, long-term illness). Particular attention was focused on a spatially-sensitive measure of the variability of deprivation scores within a wider 'locality'. There was a significant, positive relationship between age-standardised limiting, long-term illness and deprivation. The variation in area deprivation scores within the small areas themselves was also significant and positive. However, the variation in deprivation scores calculated for both an electoral ward and its contiguous neighbours (the locality) was slightly more significant. Areas with higher relative levels of in-migration also had significantly lower standardised morbidity ratios. Multivariate models showed that the deprivation score, the variation in deprivation scores for the broader locality, and the measure of migration, were all significant in combination. Residual analysis showed that many areas in London had lower levels of morbidity than expected, while electoral wards in the coal mining valleys of South Wales had higher levels than expected. We conclude that, for small areas (wards) in England and Wales, morbidity is related to deprivation, variation in deprivation within and surrounding each area, and the proportion of the population that are migrants. Variations in deprivation influence standardised morbidity rates, and policies which widen inequalities will influence health outcomes. Resource allocation based simply on measures of deprivation, which ignore population change within the area and variations in deprivation in the locality, may be inefficient.

Localized well-differentiated thyroid carcinoma: survival analysis of prognostic factors and (131)I therapy

BACKGROUND

Recommendations regarding therapeutic use of (131)I for patients with well-differentiated thyroid cancer remain controversial. Between 1969 and 1993, 1171 patients with papillary (including mixed) or follicular thyroid cancer were reported to the New Mexico Tumor Registry. Of these, 1075 cases (77.6% female, median age 41 years) were available for analysis of survival plots and previously recognized risk factors. Extent of operation was documented for 344 patients.

METHODS

One hundred twenty-seven (37%) patients underwent postoperative (131)I ablation. Median follow-up was 99 months. A proportional hazards model was constructed using age, gender, stage, histology, and use of radioiodine. The same variables plus extent of operation were examined in the smaller group.

RESULTS

Kaplan-Meier survival estimates at 12 years were 96.2% for patients younger than 45 years and 68.6% for those older than 45 years. Age, gender, and histology, but not stage, were important survival variables (P <.05). Adjusting for other risk factors, there was no apparent survival benefit associated with radioiodine following clinically appropriate thyroidectomy. Findings from the small group mirrored those of the large group.

CONCLUSIONS

(131)I may not be as efficacious as previously believed for patients with well-differentiated thyroid cancer confined to the neck.

Modelling inter-ward migration in Hereford and Worcester: the importance of housing growth and tenure

"In this paper, we use the 1991 Special Migration Statistics to analyse inter-ward flows in the British county of Hereford and Worcester. New modelling techniques...based on the Poisson distribution are used in this research which partially overcome the under-dispersion problem resulting from modelling zero and very small flows.... Analysis at this scale provides the potential for more detailed generalization about migration processes such as suburbanization, counterurbanization, intra-urban mobility, rural depopulation and the relationship between housing and demographic change at the local level. Unlike migration flows over long distances, which are often employment related, these flows are primarily motivated by residential requirements and housing type and growth are identified as key variables in the interpretation of these migration patterns."

Alteration in brain glucose metabolism induced by hypoglycaemia in man

Glucose is the usual fuel of brain tissue. As hypoglycaemia develops, a level of glycaemia is reached where glucose transport from the circulation is no longer sufficient to meet metabolic demands, and the brain signals for peripheral counter-regulatory responses and symptoms of hypoglycaemia ensue. The glycaemic threshold for these events can be shifted to lower glucose concentrations following a single episode of hypoglycaemia, and compensating central nervous system adaptations have been postulated in man. In nondiabetic subjects, rates of brain glucose uptake are initially impaired at a systemic glucose concentration of 3.6 mmol/l; whereas after 56 h of intermittent hypoglycaemia (3.0 mmol/l) brain uptake is preserved at normal rates even at 2.5 mmol/l. Increments in counter-regulatory hormones and symptoms are also triggered at lower glucose concentrations following recurrent hypoglycaemia. In 24 patients with insulin-dependent diabetes stratified into three equal groups by HbA1c value, those in the lowest third of HbA1c range had rates of brain glucose uptake at 3.0 mmol/l that were equivalent to rates measured at 5.3 mmol/l. Patients in the other HbA1c groups had rates of brain glucose uptake during hypoglycaemia that were reduced by 30% relative to normoglycaemia-comparable to reductions seen in non-diabetic subjects. Thus, alterations in glucose uptake occur in the brain in order to maintain normal brain metabolism following experimental and clinical hypoglycaemia. Because of this enhanced glucose uptake, the brain has no need to signal for counter-regulatory responses and hypoglycaemia unawareness occurs.

Effect of population mixing and socioeconomic status in England and Wales, 1979-85, on lymphoblastic leukaemia in children

OBJECTIVE

To examine the effects of migration, diversity of migrant origins, commuting, and socioeconomic status on the incidence of acute lymphoblastic leukaemia in childhood.

DESIGN

Poisson regression analysis of incidence rates in relation to the variables of interest.

SETTING

The 403 county districts of England and Wales during 1979-85.

SUBJECTS

Children aged under 15 years.

RESULTS

There were significant trends in the incidence of lymphoblastic leukaemia at ages 0-4 and 5-9 years with the proportion of children in a district who had recently entered the district. While there was no consistent relation between the proportion of recent incomers in the total population of a district and its incidence rate, the combination of higher migration with greater diversity of origins or distance moved was associated with higher incidence in both age groups. Incidence increased significantly at age 0-4 with the level of employment in a district and at age 5-9 with the proportion of households with access to a car. No significant trends were found with commuting.

CONCLUSIONS

The results for level of child migration and diversity of total migration provide evidence of an effect of population mixing on the incidence of childhood leukaemia which is not restricted to areas experiencing the most extreme levels of mixing.

Making tough resource decisions. A process for considering both values and costs

Effective resource management involves prospective decision making, including setting priorities. This enables healthcare facilities to provide services that are consistent with institutional commitments and, under some circumstances, to limit or deny services that are inconsistent with those commitments. The challenge is to apply explicit moral analysis to resource allocation efforts to ensure that facilities are treating patients consistently and fairly. Not only are allocation decisions unavoidable, they also can promote holistic, socially responsible medical practice. But current mechanisms, which are largely hidden from view and informal, can negatively affect important relationships with constituents. The just allocation of our precious healthcare resources rests on values that can either conflict with or complement one another. The core values in resource management include respect for persons, professional integrity, due process, informed consent, stewardship, and the common good. An interdisciplinary team of providers should oversee an ongoing review of resource management mechanisms. The group should meet regularly to look at how the mechanism works, what its goals are, what unit of care it evaluates, and what measurements are used to reach the goals. The measures might include severity of illness, effectiveness, cost, and social factors. Examining questions related to each of these areas can help the group determine whether an existing or proposed resource management mechanism is morally defensible.

Differential effects of physiological versus pathophysiological plasma concentrations of epinephrine and norepinephrine on ketone body metabolism and hepatic portal blood flow in man

Few studies that have examined the effects of catecholamines on ketogenesis have considered the effects of catecholamines on hepatic portal blood flow. Since hepatic blood flow is a major determinant of hepatic ketogenesis (via modification of free fatty acid availability), interpretation of these studies is difficult. To better define the relative contributions of these variables, we studied the effects of physiological and pathophysiological plasma concentrations of epinephrine and norepinephrine on plasma ketone body concentrations and hepatic portal blood flow in controlled paired studies in young healthy male volunteers. To assess the effects of physiological catecholamine concentrations, each of eight subjects received 60-minute sequential infusions of epinephrine (10 ng/kg/min) and norepinephrine (32.5 ng/kg/min) together with a control infusion of heparin (0.4 U/kg/min) separated by 60-minute washout periods. Similar increments in plasma nonesterified fatty acid ([NEFA] to approximately 1 mmol/L) were observed during each infusion. The ketotic ratios, calculated as the ratio of plasma ketone bodies to fatty acids integrated above baseline for 90 and 120 minutes, respectively, for epinephrine and norepinephrine infusions were both significantly greater (P < .005 for each) than for the heparin control infusion. To assess the effects of pathophysiological plasma catecholamine concentrations, each of eight subjects also received sequential 60-minute infusions of epinephrine 60 ng/kg/min, norepinephrine 80 ng/kg/min (plus heparin 0.1 U/kg/min), and a separate control infusion of heparin with or without Intralipid (KabiVitrum, Alameda, CA). Whereas integrated plasma fatty acid levels were approximately twofold greater than those observed in the physiological protocol, the absolute integrated ketone body response to the pathophysiological concentration of epinephrine was significantly lower than that observed for the physiological dose of the hormone (P < .05). In contrast, the ketotic ratio for norepinephrine was significantly greater (P < .005) than for both epinephrine and the control infusion of heparin with or without Intralipid. Significant (P < .01) increases above baseline fasting levels were observed in plasma glucose and immunoreactive insulin concentrations during infusion of pathophysiological concentrations of epinephrine. Because of the technical difficulties of simultaneously measuring portal blood and sampling blood frequently, studies were repeated in six additional subjects using noninvasive image-guided flowmetry to measure percentage changes in hepatic portal blood flow during catecholamine infusion. Norepinephrine reduced hepatic portal blood flow significantly at the low-physiological concentration by 12% (P < .05) and at the pathophysiological concentration by 18% (P < .05). In summary, (1) both epinephrine and norepinephrine were associated with significant ketotic effects at physiological plasma concentrations; and (2) when infused at pathophysiological concentrations, only norepinephrine exerted a significant additional ketotic effect. Since norepinephrine has a significant simultaneous effect of reducing hepatic portal blood flow, we conclude that previous studies may have underestimated the effect of norepinephrine on hepatic ketogenesis.

Prevalence and correlates of snoring and observed apneas in 5,201 older adults

The objectives of this study were to describe the prevalence of snoring, observed apneas, and daytime sleepiness in older men and women, and to describe the relationships of these sleep disturbances to health status and cardiovascular diseases (CVD). A cross-sectional design was employed to study sleep problems, CVD, general health, psychosocial factors, and medication use. The subjects were participants in the Cardiovascular Health Study, which included 5,201 adults, aged 65 and older, who were recruited from a random sample of Medicare enrollees in four U.S. communities. Study measures employed were sleep questions, echocardiography, carotid ultrasound, resting electrocardiogram, cognitive function, cardiopulmonary symptoms and diseases, depression, independent activities of daily living (IADLs), and benzodiazepine use. Thirty-three percent of the men and 19% of the women reported loud snoring, which was less frequent in those over age 75. Snoring was positively associated with younger age, marital status, and alcohol use in men, and obesity, diabetes, and arthritis in women. Snoring was not associated, however, with cardiovascular risk factors or clinical CVD in men or women. Observed apneas were reported much less frequently (13% of men and 4% women) than snoring, and they were associated with alcohol use, chronic bronchitis, and marital status in men. Observed apneas were associated with depression and diabetes in women. In both men and women, daytime sleepiness was associated with poor health, advanced age, and IADL limitations. The conclusions of the study were that loud snoring, observed apneas, and daytime sleepiness are not associated cross-sectionally with hypertension or prevalent CVD in elderly persons.

Insulin resistance limits glucose utilization and exercise tolerance in myophosphorylase deficiency and NIDDM

Myophosphorylase deficiency [McArdle's disease (MD)] produces a defect in muscle glycogenolysis in which muscular work is limited by delivery of external sources of substrate, primarily glucose and nonesterified fatty acids, to meet energy demands associated with exercise. In the present study, we evaluated an unusual patient with both MD and non-insulin-dependent diabetes mellitus. We hypothesized that insulin resistance would limit transport of extracellular glucose to skeletal muscle during exercise, resulting in impaired exercise performance that was reversible by insulin infusion. The effect of a hyperinsulinemic "euglycemic" clamp on exercise tolerance was evaluated by in vivo 31P-magnetic resonance spectroscopy as well as total work performed. We observed that insulin infusion significantly increased the rate of systemic glucose utilization (P < 0.01) and also significantly decreased the ratio of inorganic phosphate to phosphocreatine (P < 0.001) during forearm exercise compared with the control study. Insulin clamp was also associated with an increase in total work performed (56%) during exercise. Our findings demonstrate that resistance to the biological actions of insulin, as occurs in type II diabetes mellitus, leads to a defect in glucose transport that limits the availability of extracellular glucose to exercising muscle. In our subject with a substrate-limited skeletal muscle metabolism (MD), reversal of this defect in insulin-dependent glucose transport by a hyperinsulinemic euglycemic clamp was associated with significant improvement in magnetic resonance spectroscopy parameters of skeletal muscle metabolism as well as exercise performance.

Geographical variation in the referral of patients with chronic end stage renal failure for renal replacement therapy

The number of dialysis units per million population is low in the UK by comparison with other European countries, and this may affect the referral of patients for renal replacement therapy. We used a Poisson regression model to analyse the spatial distribution of all 539 adult patients resident in south-west Wales (Dyfed and West Glamorgan) who started chronic renal replacement therapy between April 1985 and March 1994. Controlling for patient age, population distribution, socio-economic variables and ethnic group, there was a significant negative relationship between referral rates and distance of residence from the renal unit for patients aged over 60 years, but not for younger patients. The prevalence of renal replacement therapy rose from 128 to 454 per million in Dyfed, and from 188 to 647 per million in West Glamorgan, between 1985 and 1995.

Brain glucose uptake and unawareness of hypoglycemia in patients with insulin-dependent diabetes mellitus

BACKGROUND

In patients with insulin-dependent diabetes mellitus (IDDM) whose treatment results in nearly normal mean plasma glucose concentrations, an unawareness of hypoglycemia can develop, and such patients are at increased risk for seizures and coma. We tested the hypothesis that during hypoglycemia, these patients would have normal glucose uptake in the brain and that consequently no sympathoadrenal activation would begin, resulting in an unawareness of hypoglycemia.

METHODS

We measured glucose uptake in the brain at plasma glucose concentrations of 105 and 54 mg per deciliter (5.8 and 3.0 mmol per liter) in 24 patients with IDDM, stratified into three groups according to their glycosylated hemoglobin values (mean [+/- SD] values, 7.2 +/- 0.5, 8.5 +/- 0.4, and 10.2 +/- 1.3 percent) and compared the values for brain glucose uptake with those measured in 15 normal subjects at plasma glucose concentrations of 85 and 55 mg per deciliter (4.2 and 3.1 mmol per liter). We also recorded the subjects' hypoglycemic-symptom scores and measured their plasma concentrations of counterregulatory hormones.

RESULTS

There was no significant change in the uptake of glucose in the brain (calculated as the uptake during hypoglycemia minus the uptake during normoglycemia) among the patients with IDDM who had the lowest glycosylated hemoglobin values (+0.6 +/- 2.0 mg [3.3 +/- 11.1 mumol] per 100 g of brain tissue per minute, P = 0.39). Conversely, glucose uptake in the brain fell in both the group with intermediate values (a decrease of 1.3 +/- 1.0 mg [7.2 +/- 5.6 mumol] per 100 g per minute, P = 0.009) and the group with the highest values (a decrease of 1.8 +/- 1.6 mg [10.0 +/- 9.0 mumol] per 100 g per minute, P = 0.01), as it did in the normal subjects (a decrease of 1.6 +/- 1.8 mg [9.0 +/- 10.1 mumol] per 100 g per minute, P = 0.003). The responses of plasma epinephrine and pancreatic polypeptide and the frequency of symptoms of hypoglycemia were lowest in the group with the lowest glycosylated hemoglobin values.

CONCLUSIONS

During hypoglycemia, patients with IDDM who have nearly normal glycosylated hemoglobin values have normal glucose uptake in the brain, which preserves cerebral metabolism, reduces the responses of counterregulatory hormones, and causes an unawareness of hypoglycemia.

Spirometry and maximal respiratory pressure references from healthy Minnesota 65- to 85-year-old women and men

OBJECTIVE

To obtain spirometry and maximal respiratory pressure (MRP) reference values for elderly persons.

DESIGN

Survey.

SETTING

General community.

PARTICIPANTS

Four hundred seventy-one healthy ambulatory white women and men age 65+ years.

METHODS

A stringent spirometry quality assurance program exceeded American Thoracic Society recommendations. A "healthy" subgroup of 176 women and 112 men between the ages of 65- and 85 years were identified by excluding those with conditions that negatively influenced FEV1 in a multiple regression analysis. Reference equations and normal ranges for FEV1, FVC, FEF25-75%, peak flow, and maximal inspiratory and expiratory pressures (MRPs) were determined from the healthy group with good quality maneuvers.

RESULTS

Less than 10% of the subjects were unable to perform three acceptable spirometry maneuvers and ten MRP maneuvers. When the age and height corrected FEV1s from this group were compared with other spirometry reference studies, mean values from the women were nearly identical to those from Morris, while these men had substantially lower FEV1 values (by 0.3- to 0.5L) than elderly men in Crapo's study. Mean peak flow was over 20% higher when compared with previous studies, suggesting greater initial expiratory effort by our subjects. The maximal inspiratory pressure (MIP) values were about 20% higher than those reported by the Cardiovascular Health Study, perhaps because five MIP maneuvers were always performed.

CONCLUSION

Spirometry and MRP reference values used for elderly patients should come from population studies using similar techniques and with large numbers of subjects over age 65 years.

Migration models incorporating interdependence of movers

"In this paper we describe a development of the Poisson model in which households are assumed to migrate independently, but the expected number of migrants is given by a Poisson distribution generalized by an empirically given household-size distribution.... The model is fitted to data on short-distance migration within the English county of Hereford and Worcester.... The data set used comes from the Special Migration Statistics (series II) produced as part of the 1981 British Census." The sparse nature of the data raises problems in assessing goodness of fit, because the deviance value is unusually low. This is tackled using simulation methodology.

Service class migration in England and Wales, 1980-81: identifying gender-specific mobility patterns

"Gendered patterns of service class migration were observed between the metropolitan counties and regional remainders within England and Wales using 1981 Census data. Observed flows were analysed in terms of the north-south migration divide and counterurbanization, and were compared to estimates derived from gravity models. More service class men than expected moved from metropolitan to non-metropolitan areas and between non-metropolitan areas. Women were less likely to move into non-metropolitan areas and were especially attracted to metropolitan destinations, notably London. These women were also more mobile within the South than service class men. It is suggested that these contrasting patterns reflect the differential geography of women's employment." (SUMMARY IN FRE AND GER)

Managed care in mental health: the ethical issues

Praise and blame of managed mental health care are on the rise on many fronts, including allegations that it could adversely affect quality of care, access to care, the physician/patient relationship, and informed patient choice. Given the heterogeneity among managed mental health care organizations--each with differing practices--it is difficult to sift the ethically defensible concerns from the indefensible ones. In this paper we identify and examine the different moral concerns about managed mental health care and mark which problems have been addressed or are in need of resolution. We also identify which problems are unique to managed mental health care.

Adaptation in brain glucose uptake following recurrent hypoglycemia

Brain glucose metabolism is impaired during hypoglycemia, but, if sustained, brain metabolism reverts to normal in animal models--data in man are lacking. We tested the hypothesis that adaptations occur to allow maintenance of normal rates of brain glucose uptake (BGU) following recurrent hypoglycemia in man. Twelve normal humans were studied over 4 days. On the initial day, arterial plasma glucose concentrations were decreased from 4.72 to 2.50 mmol/liter in five 0.56 mmol/liter steps. Cerebral blood flow, brain arteriovenous glucose difference, BGU, and cognitive function were quantitated at each step. BGU was initially impaired at the 3.61 mmol/liter glucose step (P = 0.04) and was antedated by increments in epinephrine that began at 4.16 mmol/liter (P = 0.03). The onset of hypoglycemic symptoms occurred during the 3.61 mmol/liter glucose step (P = 0.02), whereas tests of cognitive function generally deteriorated at the 3.05 mmol/liter step (P < 0.05). During the next 56 hr, mean glucose concentrations were kept at 2.9 +/- 0.1 mmol/liter and reached normal only during meals. The stepped clamp protocol was repeated beginning at 4.16 mmol/liter on the last day. No decrement in BGU was observed at any step; cognitive function was preserved until significantly lower glucose concentrations on the final day relative to the first (P = 0.04). Subjects remained asymptomatic of hypoglycemia until they reached a glucose concentration of 2.50 mmol/liter (P < 0.001 vs. day 1), while initial increments in all counterregulatory hormones were forestalled to lower glucose steps than on day 1. Therefore, adaptations occur that allow normal BGU and cerebral function to be maintained during recurrent systemic hypoglycemia. Counterregulatory events that should result in symptoms of hypoglycemia and increments in endogenous glucose production are prevented until extremely subnormal glucose concentrations.