The Relation Between Cognitive Performance and Symptom Factors Following Concussion

Purpose

The purpose of this study was to explore if symptom factors are related to cognitive outcomes. Prior studies have examined the relationship of individual symptoms to cognition. However, the relation between empirically-derived symptom factors and cognitive outcomes has yet to be explored.

Methods

Data were extracted via retrospective chart review of 691 patients (aged 10–24, mean: 14.99±2.63). Participants completed ImPACT and the PCSS within 14 days of injury (mean: 9.27±3.37). Predictors were PCSS factor scores of Cognitive-Fatigue-Migraine (CFM), Affective (AFF), Somatic (SOM), and Sleep (SLP) (Kontos et al., 2012). Outcomes examined were ImPACT composite scores. Univariate analyses were performed and values with p < 0.10 were entered into stepwise linear regression (LR) models. Retained predictors in each LR model had p values <.05.

Results

Verbal memory was predicted by CFM, SOM, age, and gender. Visual memory was predicted by CFM and SOM. Visual motor speed was predicted by age, gender, CFM, SOM, and AFF. Reaction time was best predicted by SOM, CFM, and age. The variance explained was fairly small (0.08 to 0.21). SLP was not a significant predictor in any LR.

Conclusion

CFM and SOM factors were most predictive of lower cognitive performance, similar to prior studies linking dizziness to longer recovery and post-traumatic migraine to worse cognitive performance. These findings underscore the clinical importance of diverse symptom assessment and injury education. Higher CFM and SOM scores may also serve as proxy for injury severity, which we would expect to be associated with worse cognitive performance.

Influence of maternal and paternal IQ on offspring health and health behaviours: evidence for some trans-generational associations using the 1958 British birth cohort study

PURPOSE

Individuals scoring poorly on tests of intelligence (IQ) have been reported as having increased risk of morbidity, premature mortality, and risk factors such as obesity, high blood pressure, poor diet, alcohol and cigarette consumption. Very little is known about the impact of parental IQ on the health and health behaviours of their offspring.

METHODS

We explored associations of maternal and paternal IQ scores with offspring television viewing, injuries, hospitalisations, long standing illness, height and BMI at ages 4 to 18 using data from the National Child Development Study (1958 birth cohort).

RESULTS

Data were available for 1446 mother-offspring and 822 father-offspring pairs. After adjusting for potential confounding/mediating factors, the children of higher IQ parents were less likely to watch TV (odds ratio (95% confidence interval) for watching 3+ vs. less than 3hours per week associated with a standard deviation increase in maternal or paternal IQ: 0.75 (0.64, 0.88) or 0.78 (0.64, 0.95) respectively) and less likely to have one or more injuries requiring hospitalisation (0.77 (0.66, 0.90) or 0.72 (0.56, 0.91) respectively for maternal or paternal IQ).

CONCLUSIONS

Children whose parents have low IQ scores may have poorer selected health and health behaviours. Health education might usefully be targeted at these families.

Associations between types of dietary fat and fish intake and risk of stroke in the Caerphilly Prospective Study (CaPS)

BACKGROUND

Few population-based longitudinal studies on diet and stroke have been conducted, and associations between dietary fat and fish intake and risk of stroke are unclear.

OBJECTIVES

To prospectively examine relationships between intakes of total fat, saturated fat, unsaturated fat, white fish and oily fish and risk of stroke in a well-defined population of 2710 middle-aged men.

STUDY DESIGN

Prospective cohort study.

METHODS

Detailed information on health and lifestyle factors was collected via interview, and diet was assessed on three occasions using a food frequency questionnaire. Stroke ascertainment was by self-report and inspection of clinical records. Extracted data were assessed by two independent experts.

RESULTS

During a median follow-up of 18 years, 225 strokes (209 ischaemic and 19 haemorrhagic) were eligible for inclusion in the analyses. For most recent diet (i.e. food frequency questionnaire data collected immediately prior to the stroke event), there was a slightly lower risk of stroke with higher intakes of unsaturated fat and oily fish. Multiple adjusted hazard ratios (HRs) for the lowest vs highest quintiles of unsaturated fat and oily fish intakes were 0.66 [95% confidence interval (CI) 0.41-1.05, P trend = 0.13] and 0.66 (95% CI 0.41-1.05, P trend = 0.09), respectively. Baseline and cumulative diets showed a slightly higher risk of stroke with higher intake of white fish; HRs for the lowest vs highest quintiles were 1.16 (95% CI 0.76-1.77, P trend = 0.22) and 1.28 (95% CI 0.77-2.13, P trend = 0.48), respectively.

CONCLUSIONS

Overall, strong associations were not found between intakes of different types of fat and fish and risk of stroke in middle-aged men. The inverse associations between unsaturated fat and oily fish intakes and risk of stroke were weak, but the direction of association was broadly consistent with other studies; however, these relatively weak associations were not conventionally statistically significant.

The association of childhood height, leg length and other measures of skeletal growth with adult cardiovascular disease: the Boyd-Orr cohort

BACKGROUND

Taller adults have a reduced risk of cardiovascular disease, and there is some evidence that pre-adolescent exposures, indexed by leg length, underlie this association. Associations with other aspects of skeletal size in childhood have not previously been investigated.

METHODS

We have examined associations of cardiovascular mortality and morbidity with childhood height, shoulder breadth, leg, trunk and foot length using a cohort of children whose families participated in a 1937-9 survey of diet and health followed up for 59 years.

RESULTS

Altogether 2642 traced participants had at least one anthropometric measurement; a subsample (n=1043), completed the Rose angina questionnaire and provided information about doctor-diagnosed ischaemic heart disease (IHD) in 1997-8. Childhood stature was weakly inversely associated with cardiovascular mortality, and leg length was the component with the strongest associations. There was evidence from secondary analyses that childhood anthropometric measurements were inversely related to early (age <65 years) rather than late cardiovascular mortality. Childhood stature was inversely associated with self-reported IHD and associations with leg length were strongest. Associations were somewhat attenuated in models including terms for having been breastfed and socioeconomic position.

CONCLUSION

Pre-adult exposures are more strongly associated with cardiovascular morbidity than mortality, and they affect premature cardiovascular mortality more than later mortality.

Intelligence in early adulthood and subsequent risk of unintentional injury over two decades: cohort study of 1 109 475 Swedish men

BACKGROUND

There is growing evidence of an inverse association between intelligence (IQ) and unintentional injuries.

METHODS

Analyses are based on a cohort of 1 109 475 Swedish men with IQ measured in early adulthood. Men were followed up for an average 24 years, and hospital admissions for unintentional injury were recorded.

RESULTS

198 133 (17.9%) men had at least one hospital admission for any unintentional injury during follow-up. The most common cause of unintentional injury was falling, followed by road accidents, poisoning, fire and drowning. In addition, 14 637 (1.3%) men had at least one admission for complications of medical care. After adjusting for confounding variables, lower IQ scores were associated with an elevated risk of any unintentional injury (HR (95% CI) per SD decrease in IQ: 1.15 (1.14 to 1.15)) and of cause-specific injuries other than drowning (poisoning (1.53 (1.49 to 1.57)), fire (1.36 (1.31 to 1.41)), road traffic accidents (1.25 (1.23 to 1.26)), medical complications (1.20 (1.18 to 1.22)) and falling (1.17 (1.16 to 1.18))). These gradients were stepwise across the full IQ range.

CONCLUSIONS

Low IQ scores in early adulthood were associated with a subsequently increased risk of unintentional injury. A greater understanding of mechanisms underlying these associations may provide opportunities and strategies for prevention.

Collarless polished tapered stem: clinical and radiological results at a minimum of ten years' follow-up

We retrospectively reviewed 175 patients (191 hips) who had undergone primary cemented total hip replacement between November 1992 and November 1995 using a collarless polished double-tapered femoral component after a minimum of ten years (mean 11.08; 10 to 12.8). All stems were implanted using contemporary cementing techniques with a distal cement restrictor, pressurised lavage, retrograde cementing with a gun and proximal pressurisation. Clinical outcome was assessed using the Harris Hip score. Radiological analysis was performed on calibrated plain radiographs taken in two planes. Complete radiological data on 110 patients (120 hips) and clinical follow-up on all the surviving 111 patients (122 hips) was available. The fate of all the hips was known. At final follow-up, the mean Harris Hip score was 86 (47 to 100), and 87 of 116 patients (75%) had good or excellent scores. Survival with revision of the stem for aseptic loosening as the endpoint was 100%; and survival with revision of the stem for any reason was 95.9% (95% confidence interval 87.8 to 96.8) at ten years. All the stems subsided vertically at the stem-cement interface in a predictable pattern, at an overall mean rate of 0.18 mm per year (0.02 to 2.16), but with a mean rate of 0.80 mm (0.02 to 2.5) during the first year. The mean total subsidence was 1.95 mm (0.21 to 24). Only three stems loosened at the cement-bone interface. There was excellent preservation of proximal femoral bone stock. There was a high incidence of Brooker III and IV heterotopic ossification affecting 25 patients (22%). The collarless polished tapered stem has an excellent clinical and radiological outcome at a minimum of ten years' follow-up. The pattern and magnitude of subsidence of the stem within the cement mantle occurred in a predictable pattern, consistent with the design philosophy.

Ten-year life expectancy after primary total hip replacement

We determined the ten-year life expectancy of 5831 patients who had undergone 6653 elective primary total hip replacements at a regional orthopaedic centre between April 1993 and October 2004. Using hospital, general practitioner and the local health authority records, we recorded the dates of death for those who died following surgery. The mean age at operation was 67 years (13 to 96) with a male:female ratio of 2:3. Of 1154 patients with a ten-year follow-up 340 (29.5%) had died a mean of 5.6 years (0 to 10) after surgery. Using Kaplan-Meier curves, the ten-year survival was 89% in patients under 65 years at surgery, 75% in patients aged between 65 and 74 years, and 51% in patients over 75. The standardised mortality rates were considerably higher for patients under 45 years, 20% higher for those between 45 and 64 years, and steadily reduced in patients aged 65 and over. The survival of cemented hip replacement derived from the Swedish Hip Arthroplasty Register Annual Report 2004 exceeds the life expectancy of patients over the age of 60 in our area, suggesting that cemented hip replacement is the procedure of choice in this population.

Determinants of outcome in critically ill octogenarians after surgery: an observational study

BACKGROUND

The population in the UK is growing older and the number of elderly patients cared for on intensive care units (ICU) is increasing. This study was designed to identify risk factors for mortality in critically ill patients of >80 yr of age after surgery.

METHODS

We identified 275 patients, aged 80 yr or greater, admitted to the ICU after surgery. After exclusions, 255 were selected for further analysis. Multivariate analysis was then performed to determine the covariates associated with hospital mortality.

RESULTS

The overall ICU and hospital mortality was 20.4% and 33.3%, respectively. Patients who received i.v. vasoactive drugs on days 1 and 2 had hospital mortality of 54.4% and 60.5%, respectively. Multivariate analysis showed that requirement for i.v. vasoactive drugs within the first 24 h on ICU [odds ratio (OR) 4.29; 95% CI, 2.35-7.84, P<0.001] and requirement for i.v. vasoactive drugs for a further 24 h (OR 3.63; 95% CI, 1.58-8.37, P<0.01) were associated with hospital mortality. The requirement for i.v. vasoactive drugs was also strongly associated with hospital mortality in all the subgroups studied (elective surgery, emergency surgery, and emergency laparotomy).

CONCLUSIONS

For patients aged 80 yr and more, admitted to ICU after surgery, the requirement for i.v. vasoactive drugs in the first and second 24 h was the strongest predictor of hospital mortality.

The Exeter Universal stem: a minimum ten-year review from an independent centre

We reviewed 142 consecutive primary total hip replacements implanted into 123 patients between 1988 and 1993 using the Exeter Universal femoral stem. A total of 74 patients (88 hips) had survived for ten years or more and were reviewed at a mean of 12.7 years (10 to 17). There was no loss to follow-up. The rate of revision of the femoral component for aseptic loosening and osteolysis was 1.1% (1 stem), that for revision for any cause was 2.2% (2 stems), and for re-operation for any cause was 21.6% (19 hips). Re-operation was because of failure of the acetabular component in all but two hips. All but one femoral component subsided within the cement mantle to a mean of 1.52 mm (0 to 8.3) at the final follow-up. One further stem had subsided excessively (8 mm) and had lucent lines at the cement-stem and cement-bone interfaces. This was classified as a radiological failure and is awaiting revision. One stem was revised for deep infection and one for excessive peri-articular osteolysis. Defects of the cement mantle (Barrack grade C and D) were found in 28% of stems (25 hips), associated with increased subsidence (p = 0.01), but were not associated with endosteal lysis or failure. Peri-articular osteolysis was significantly related to the degree of polyethylene wear (p < 0.001), which was in turn associated with a younger age (p = 0.01) and male gender (p < 0.001). The use of the Exeter metal-backed acetabular component was a notable failure with 12 of 32 hips (37.5%) revised for loosening. The Harris-Galante components failed with excessive wear, osteolysis and dislocation with 15% revised (5 of 33 hips). Only one of 23 hips with a cemented Elite component (4%) was revised for loosening and osteolysis. Our findings show that the Exeter Universal stem implanted outside the originating centre has excellent medium-term results.

The association of fetal and childhood growth with risk of schizophrenia. Cohort study of 720,000 Swedish men and women

Previous investigations of the association of schizophrenia with patterns of pre- and post-natal growth have been based on small numbers of cases or have not taken account of the effects of prematurity on birthweight. We investigated the association of fetal growth with schizophrenia in a large cohort of Swedish males and females. We linked data from the Swedish Medical Birth Register (1973-1980), Inpatient and Discharge Register (1988-2002), Military Service Conscription Register (1990-1997), and the Population and Housing Censuses (1970 and 1990). Altogether 719,476 males and females were followed up from the age of 16 for a mean of 9.9 years. There were 736 incident cases of schizophrenia. Even in models that did not control for gestational age there was little evidence of an association between birthweight and schizophrenia (hazard ratio per kg increase in birthweight: 0.90 (95% CI 0.78 to 1.03); the hazard ratio in babies weighing <2.5 kg compared to 3.5-4.0 kg was 1.29 (95% CI 0.85 to 1.96). There was an inverse association of birth length with schizophrenia across the range of birth lengths. Short babies were at an increased risk (hazard ratio per 10 cm increase in birth length: 0.53, 95% CI 0.31 to 0.89 (fully adjusted model)). All associations were little changed when analyses were restricted to term (>36 week gestation) babies. In males, low body mass index and short height at age 18 were associated with increased risk. There is some evidence that patterns of risk in relation to fetal growth differ depending on post-natal growth patterns: the increased risk associated with low body mass index was restricted to long babies who became light adults. The exposures underlying these associations and the biological mechanisms mediating them require clarification.

Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies

OBJECTIVE

To determine the risk of lung cancer associated with exposure at home to the radioactive disintegration products of naturally occurring radon gas.

DESIGN

Collaborative analysis of individual data from 13 case-control studies of residential radon and lung cancer.

SETTING

Nine European countries.

SUBJECTS

7148 cases of lung cancer and 14,208 controls.

MAIN OUTCOME MEASURES

Relative risks of lung cancer and radon gas concentrations in homes inhabited during the previous 5-34 years measured in becquerels (radon disintegrations per second) per cubic metre (Bq/m3) of household air.

RESULTS

The mean measured radon concentration in homes of people in the control group was 97 Bq/m3, with 11% measuring > 200 and 4% measuring > 400 Bq/m3. For cases of lung cancer the mean concentration was 104 Bq/m3. The risk of lung cancer increased by 8.4% (95% confidence interval 3.0% to 15.8%) per 100 Bq/m3 increase in measured radon (P = 0.0007). This corresponds to an increase of 16% (5% to 31%) per 100 Bq/m3 increase in usual radon--that is, after correction for the dilution caused by random uncertainties in measuring radon concentrations. The dose-response relation seemed to be linear with no threshold and remained significant (P = 0.04) in analyses limited to individuals from homes with measured radon < 200 Bq/m3. The proportionate excess risk did not differ significantly with study, age, sex, or smoking. In the absence of other causes of death, the absolute risks of lung cancer by age 75 years at usual radon concentrations of 0, 100, and 400 Bq/m3 would be about 0.4%, 0.5%, and 0.7%, respectively, for lifelong non-smokers, and about 25 times greater (10%, 12%, and 16%) for cigarette smokers.

CONCLUSIONS

Collectively, though not separately, these studies show appreciable hazards from residential radon, particularly for smokers and recent ex-smokers, and indicate that it is responsible for about 2% of all deaths from cancer in Europe.

35 PRODUCTION OF CLONED MINIATURE CALVES USING CYTOPLASTS FROM COWS OF STANDARD SIZE

Numerous genetically similar cattle for use in research or teaching can be produced with chromatin transfer technology (Sullivan et al. 2004 Biol. Reprod. 70, 146–153). Miniature cattle can provide advantageous biotechnological models for teaching and study of human and animal diseases. Miniature cattle are approximately one fourth the size of standard cattle and, therefore, represent a potentially less expensive, safer, and more easily managed animal model. Our limited attempts to reproduce miniature cattle via in vivo and in vitro production of embryos resulted in poor response to superovulation and logistical challenges in recovering embryos or oocytes due to the small size of the animals. Thus, the purpose of this study was to evaluate the potential of embryos derived by chromatin transfer from fibroblasts of a miniature cow and cytoplasts from cows of standard size to produce viable offspring after transfer into recipient cows of standard size. The donor of somatic cells was a heifer that weighed 7.7 kg at birth. Chromatin transfer resulted in 19% (82/428) blastocyst formation. A total of 66 cloned blastocysts (65 excellent/good quality, 1 fair quality) were transferred into 26 synchronized recipients. While ultrasound revealed 13 pregnancies prior to 67 days of gestation, only 4 pregnancies of 5 fetuses were maintained beyond 100 days. Parturition was induced with dexamethasone and prostaglandin on Day 286 of gestation. One singleton (12.3 kg) and a set of twins (10.2 and 11.1 kg) were healthy at birth and normal at 1 week of age. Two fully developed singletons, weighing 21.4 and 13.6 kg, died in utero. The latter fetus exhibited a fixed dorsolateral deviation of the neck that complicated delivery despite a caudal obstetrical presentation. No abnormalities were noted in the size or structure of any placenta. Our results indicate that healthy miniature calves can be gestated by recipient cows of standard size after transfer of embryos derived by chromatin transfer. Unfortunately, the fetal wastage, fetal anomalies, and stillbirths observed with standard sized cattle also may occur.

Associations of height, leg length, and lung function with cardiovascular risk factors in the Midspan Family Study

BACKGROUND

Taller people and those with better lung function are at reduced risk of coronary heart disease (CHD). Biological mechanisms for these associations are not well understood, but both measures may be markers for early life exposures. Some studies have shown that leg length, an indicator of pre-pubertal nutritional status, is the component of height most strongly associated with CHD risk. Other studies show that height-CHD associations are greatly attenuated when lung function is controlled for. This study examines (1) the association of height and the components of height (leg length and trunk length) with CHD risk factors and (2) the relative strength of the association of height and forced expiratory volume in one second (FEV(1)) with risk factors for CHD.

SUBJECTS AND METHODS

Cross sectional analysis of data collected at detailed cardiovascular screening examinations of 1040 men and 1298 women aged 30-59 whose parents were screened in 1972-76. Subjects come from 1477 families and are members of the Midspan Family Study.

SETTING

The towns of Renfrew and Paisley in the West of Scotland.

RESULTS

Taller subjects and those with better lung function had more favourable cardiovascular risk factor profiles, associations were strongest in relation to FEV(1). Higher FEV(1) was associated with lower blood pressure, cholesterol, glucose, fibrinogen, white blood cell count, and body mass index. Similar, but generally weaker, associations were seen with height. These associations were not attenuated in models controlling for parental height. Longer leg length, but not trunk length, was associated with lower systolic and diastolic blood pressure. Longer leg length was also associated with more favourable levels of cholesterol and body mass index than trunk length.

CONCLUSIONS

These findings provide indirect evidence that measures of lung development and pre-pubertal growth act as biomarkers for childhood exposures that may modify an individual's risk of developing CHD. Genetic influences do not seem to underlie height-CHD associations.

The long-term effect of dietary advice in men with coronary disease: follow-up of the Diet and Reinfarction trial (DART)

OBJECTIVE

To assess the long-term effect of dietary advice on diet and mortality after a randomised trial of men with a recent history of myocardial infarction.

DESIGN

Questionnaire survey and mortality follow-up after a trial of dietary advice.

SETTING

Twenty-one hospitals in south Wales and south-west England.

SUBJECTS

Former participants in the Diet and Reinfarction Trial.

MAIN OUTCOME MEASURES

Current fish intake and cereal fibre intake. All-cause mortality, stroke mortality and coronary mortality.

RESULTS

By February 2000, after 21147 person years of follow-up, 1083 (53%) of the men had died. Completed questionnaires were obtained from 879 (85%) of the 1030 men alive at the beginning of 1999. Relative increases in fish and fibre intake were still present at 10 y but were much smaller. The early reduction in all-cause mortality observed in those given fish advice (unadjusted hazard 0.70 (95% CI 0.54, 0.92)) was followed by an increased risk over the next 3 y (unadjusted hazard 1.31 (95% CI 1.01, 1.70). Fat and fibre advice had no clear effect on coronary or all-cause mortality. The risk of stroke death was increased in the fat advice group-the overall unadjusted hazard was 2.03 (95% CI 1.14, 3.63).

CONCLUSIONS

In this follow-up of a trial of intensive dietary advice following myocardial infarction we did not observe any substantial long-term survival benefit. Further trials of fish and fibre advice are feasible and necessary to clarify the role of these foods in coronary disease.

Subgroup analyses in randomised controlled trials: quantifying the risks of false-positives and false-negatives

BACKGROUND

Subgroup analyses are common in randomised controlled trials (RCTs). There are many easily accessible guidelines on the selection and analysis of subgroups but the key messages do not seem to be universally accepted and inappropriate analyses continue to appear in the literature. This has potentially serious implications because erroneous identification of differential subgroup effects may lead to inappropriate provision or withholding of treatment.

OBJECTIVES

(1) To quantify the extent to which subgroup analyses may be misleading. (2) To compare the relative merits and weaknesses of the two most common approaches to subgroup analysis: separate (subgroup-specific) analyses of treatment effect and formal statistical tests of interaction. (3) To establish what factors affect the performance of the two approaches. (4) To provide estimates of the increase in sample size required to detect differential subgroup effects. (5) To provide recommendations on the analysis and interpretation of subgroup analyses.

METHODS

The performances of subgroup-specific and formal interaction tests were assessed by simulating data with no differential subgroup effects and determining the extent to which the two approaches (incorrectly) identified such an effect, and simulating data with a differential subgroup effect and determining the extent to which the two approaches were able to (correctly) identify it. Initially, data were simulated to represent the 'simplest case' of two equal-sized treatment groups and two equal-sized subgroups. Data were first simulated with no differential subgroup effect and then with a range of types and magnitudes of subgroup effect with the sample size determined by the nominal power (50-95%) for the overall treatment effect. Additional simulations were conducted to explore the individual impact of the sample size, the magnitude of the overall treatment effect, the size and number of treatment groups and subgroups and, in the case of continuous data, the variability of the data. The simulated data covered the types of outcomes most commonly used in RCTs, namely continuous (Gaussian) variables, binary outcomes and survival times. All analyses were carried out using appropriate regression models, and subgroup effects were identified on the basis of statistical significance at the 5% level.

RESULTS

While there was some variation for smaller sample sizes, the results for the three types of outcome were very similar for simulations with a total sample size of greater than or equal to 200. With simulated simplest case data with no differential subgroup effects, the formal tests of interaction were significant in 5% of cases as expected, while subgroup-specific tests were less reliable and identified effects in 7-66% of cases depending on whether there was an overall treatment effect. The most common type of subgroup effect identified in this way was where the treatment effect was seen to be significant in one subgroup only. When a simulated differential subgroup effect was included, the results were dependent on the nominal power of the simulated data and the type and magnitude of the subgroup effect. However, the performance of the formal interaction test was generally superior to that of the subgroup-specific analyses, with more differential effects correctly identified. In addition, the subgroup-specific analyses often suggested the wrong type of differential effect. The ability of formal interaction tests to (correctly) identify subgroup effects improved as the size of the interaction increased relative to the overall treatment effect. When the size of the interaction was twice the overall effect or greater, the interaction tests had at least the same power as the overall treatment effect. However, power was considerably reduced for smaller interactions, which are much more likely in practice. The inflation factor required to increase the sample size to enable detection of the interaction with the same power as the overall effect varied with the size of the interaction. For an interaction of the same magnitude as the overall effect, the inflation factor was 4, and this increased dramatically to of greater than or equal to 100 for more subtle interactions of < 20% of the overall effect. Formal interaction tests were generally robust to alterations in the number and size of the treatment and subgroups and, for continuous data, the variance in the treatment groups, with the only exception being a change in the variance in one of the subgroups. In contrast, the performance of the subgroup-specific tests was affected by almost all of these factors with only a change in the number of treatment groups having no impact at all.

CONCLUSIONS

While it is generally recognised that subgroup analyses can produce spurious results, the extent of the problem is almost certainly under-estimated. This is particularly true when subgroup-specific analyses are used. In addition, the increase in sample size required to identify differential subgroup effects may be substantial and the commonly used 'rule of four' may not always be sufficient, especially when interactions are relatively subtle, as is often the case. CONCLUSIONS--RECOMMENDATIONS FOR SUBGROUP ANALYSES AND THEIR INTERPRETATION: (1) Subgroup analyses should, as far as possible, be restricted to those proposed before data collection. Any subgroups chosen after this time should be clearly identified. (2) Trials should ideally be powered with subgroup analyses in mind. However, for modest interactions, this may not be feasible. (3) Subgroup-specific analyses are particularly unreliable and are affected by many factors. Subgroup analyses should always be based on formal tests of interaction although even these should be interpreted with caution. (4) The results from any subgroup analyses should not be over-interpreted. Unless there is strong supporting evidence, they are best viewed as a hypothesis-generation exercise. In particular, one should be wary of evidence suggesting that treatment is effective in one subgroup only. (5) Any apparent lack of differential effect should be regarded with caution unless the study was specifically powered with interactions in mind. CONCLUSIONS--RECOMMENDATIONS FOR RESEARCH: (1) The implications of considering confidence intervals rather than p-values could be considered. (2) The same approach as in this study could be applied to contexts other than RCTs, such as observational studies and meta-analyses. (3) The scenarios used in this study could be examined more comprehensively using other statistical methods, incorporating clustering effects, considering other types of outcome variable and using other approaches, such as Bootstrapping or Bayesian methods.

Secular trends in antidepressant prescribing in the UK, 1975-1998

BACKGROUND

We have examined secular trends in age- and sex-specific prescribing of antidepressants to determine whether these mirror changes in other population measures of mental health.

METHOD

An analysis was carried out of age- and sex-specific rates of antidepressant prescribing by a representative sample or panel of UK general practitioners (GPs) in the period 1975-1998.

RESULTS

The number of antidepressant prescriptions issued increased more than twofold in the period 1975-1998 and, in 1998, a total of 23.4 million antidepressant prescriptions were issued by GPs in the United Kingdom. Rates of antidepressant prescribing increased markedly in all age and sex groups with as much as a threefold increase in the older age groups. With the exception of 12-19-year-olds, these increases have been more marked in males, although absolute levels of prescribing are still at least two times higher in females.

CONCLUSIONS

Antidepressant prescribing has increased in all age and sex groups. This indicates either that there have been changes in the presentation, recognition and management of depression in general practice or that the prevalence of depression has increased, or a combination of these two phenomena. The higher prescribing rate in females is in keeping with evidence from psychiatric morbidity surveys suggesting that women experience higher levels of psychiatric morbidity than men. Decreases in the ratio of female to male prescribing, however, support other data indicating that, relative to females, the mental health of young males has declined in recent years. Changes in patterns of help-seeking may also contribute to the observed trends.

Urinary incontinence in older people in the community: a neglected problem?

BACKGROUND

The prevalence and impact of urinary incontinence has been investigated much less in older men than in older women. It is suggested that those who perceive that their daily lives are affected should have priority for services. However, many people do not seek medical help, even though they may be severely affected.

AIM

To investigate unmet need in relation to the prevalence and impact on everyday life of urinary incontinence in men and women over the age of 65 years.

DESIGN OF STUDY

Cross-sectional survey to measure prevalence of urinary incontinence, the impact on people's lives, use of protection, and health services.

SETTING

Stratified random sample of 2000 community-living elderly (equal numbers of men and women, aged 65 to 74 years and over 75 years) in 11 general practices in a British city.

RESULTS

The response rate was 79%. The overall prevalence of incontinence in the previous month was 31% for women and 23% for men. Women generally had more severe frequency of incontinence and a greater degree of wetness than men. Protection use was greater in women than in men. Only 40% of men and 45% of women with incontinence had accessed health services. Significant predictors of the use of health services were: incontinence reported as a problem, increased frequency of incontinence, and greater degree of wetness. About one-third of people who leaked with severe frequency or who reported that it was a problem had not accessed NHS services for incontinence.

CONCLUSIONS

Urinary incontinence is a common problem for older men and women living in the community and can have a deleterious effect on their lives. There is the opportunity to improve the lives of many older people with urinary incontinence, probably by a combination of increased public, patient, and professional awareness that should lead to earlier presentation and initiation of effective care.

Lung cancer and cigarette smoking in Europe: an update of risk estimates and an assessment of inter-country heterogeneity

Ten case-control studies have been carried out in 6 European countries to investigate the major risk factors for lung cancer. Carcinogenic effect from cigarette smoke was the most relevant interest in our study, which has included 7,609 cases of lung cancer and 10,431 controls, mainly population based. The results indicate elevated odds ratios (ORs; 23.9 among men and 8.7 among women) with attributable risks exceeding 90% for men and close to 60% for women. A large, and statistically significant, variability of the results across countries was detected after adjusting for the most common confounding variables, and after controlling, at least in part, for the instability of the ORs due to the small number of non-smokers in some of the study subsets. This pattern of lung cancer risk associated with cigarettes smoke, across different European regions, reflects inherent characteristics of the studies as well as differences in smoking habits, particularly calendar periods of starting, and it is likely to have been influenced by effect modifiers like indoor radon exposure, occupation, air pollution and dietary habits.

Diet, smoking and lung cancer: a case-control study of 1000 cases and 1500 controls in South-West England

We have examined the relationship between diet and lung cancer in a case-control study of 982 cases of lung cancer and 1486 population controls in south-west England in which subjects were interviewed personally about their smoking habits and their consumption of foods and supplements rich in retinol or carotene. Analyses were performed for 15 dietary variables, including intake of pre-formed retinol and carotene. There were significant associations (P< 0.01) with lung cancer risk for 13 of the variables, eight of which remained after adjustment for smoking. When the 15 variables were considered simultaneously, independent significant associations remained for 5: pre-formed retinol (increased risk), and fish liver oil, vitamin pills, carrots and tomato sauce (decreased risk). It is unlikely that all five associations represent biological effects, or that they can all be explained by residual confounding by smoking, or by biases. We conclude that there is at least one as yet unidentified factor that is causally related to lung cancer risk and of considerable importance in terms of attributable risk in this population.

Birth dimensions of offspring, premature birth, and the mortality of mothers

A person's birthweight is inversely related to their cardiovascular disease (CVD) mortality risk, and preliminary data suggest that the birthweights of offspring are also inversely related to parental CVD mortality risk. In a cohort of pregnant Finnish women, we assessed the relation between birth dimensions of the offspring and maternal characteristics, and subsequent mortality. Maternal CVD mortality was inversely related to the birthweight of offspring and women having premature deliveries were also at increased CVD risk. Breast-cancer mortality was positively associated with ponderal index of offspring.

Lung cancer and cigarette smoking in women: a multicenter case-control study in Europe

The association between cigarette smoking and lung cancer risk in women was investigated within the framework of a case-control study in 9 centres from 6 European countries. Cases were 1,556 women up to 75 years of age with histologically confirmed primary lung cancer; 2, 450 controls with age distribution similar to cases were selected. The predominant cell type was adenocarcinoma (33.5%), with similar proportions for squamous-cell type (26.4%) and small-cell carcinoma (22.3%). Overall, smoking cigarettes at any time was associated with a 5-fold increase in lung cancer risk (odds ratio 5.21, 95% confidence interval 4.49-6.04); corresponding figures for current smoking habits were 8.94, 7.54-10.6. The association showed a dose-response relationship with duration of the habit and daily and cumulative lifetime smoking. A significant excess risk of 70% was associated with every 10 pack-years smoked. After 10 years of smoking cessation, the relative risk decreased to 20% compared to current smokers. The following characteristics were associated with a higher relative risk: inhalation of smoke, smoking non-filter cigarettes, smoking dark-type cigarettes and starting at young age. The association was observed for all major histological types, being the strongest for small-cell type carcinoma, followed by squamous-cell type and the lowest for adenocarcinoma. The proportion of lung-cancer cases in the population attributable to cigarette smoking ranged from 14% to 85%. We concluded that women share most features of the association between cigarette smoking and lung cancer observed in men.

Occupational risks for lung cancer among nonsmokers

We conducted a case-control study in 12 European study centers to evaluate the role of occupational risk factors among nonsmokers. We obtained detailed occupational histories from 650 nonsmoking cases (509 females/141 males) and 1,542 nonsmoking controls (1,011 females/531 males). On the basis of an a priori definition of occupations and industries that are known (list A) or suspected (list B) to be associated with lung carcinogenesis, we calculated odds ratios (ORs) for these occupations, using unconditional logistic regression models and adjusting for sex, age, and center effects. Among nonsmoking men, an excess relative risk was observed among those who had worked in list-A occupations [OR = 1.52; 95% confidence interval (C) = 0.78-2.97] but not in list-B occupations (OR = 1.05; 95%), CI = 0.60-1.83). Among nonsmoking women, there was an elevation of risk for list-A occupations (OR = 1.50; 95% CI = 0.49-4.53), although this estimate was imprecise, given that less than 1% of cases and controls were exposed. Exposure to list-B occupations was associated with an increase in relative risk (OR = 1.69; 95% CI = 1.09-2.63) in females, but not in males. Women who had been laundry workers or dry cleaners had an OR of 1.83 (95% CI = 0.98-3.40). Our findings confirm that certain occupational exposures are associated with an increased risk for lung cancer among both female and male nonsmokers; however, knowledge on occupational lung carcinogens is biased toward agents to which mainly men are exposed.

Smoking, smoking cessation, and lung cancer in the UK since 1950: combination of national statistics with two case-control studies

OBJECTIVE AND DESIGN

To relate UK national trends since 1950 in smoking, in smoking cessation, and in lung cancer to the contrasting results from two large case-control studies centred around 1950 and 1990.

SETTING

United Kingdom.

PARTICIPANTS

Hospital patients under 75 years of age with and without lung cancer in 1950 and 1990, plus, in 1990, a matched sample of the local population: 1465 case-control pairs in the 1950 study, and 982 cases plus 3185 controls in the 1990 study.

MAIN OUTCOME MEASURES

Smoking prevalence and lung cancer.

RESULTS

For men in early middle age in the United Kingdom the prevalence of smoking halved between 1950 and 1990 but the death rate from lung cancer at ages 35-54 fell even more rapidly, indicating some reduction in the risk among continuing smokers. In contrast, women and older men who were still current smokers in 1990 were more likely than those in 1950 to have been persistent cigarette smokers throughout adult life and so had higher lung cancer rates than current smokers in 1950. The cumulative risk of death from lung cancer by age 75 (in the absence of other causes of death) rose from 6% at 1950 rates to 16% at 1990 rates in male cigarette smokers, and from 1% to 10% in female cigarette smokers. Among both men and women in 1990, however, the former smokers had only a fraction of the lung cancer rate of continuing smokers, and this fraction fell steeply with time since stopping. By 1990 cessation had almost halved the number of lung cancers that would have been expected if the former smokers had continued. For men who stopped at ages 60, 50, 40, and 30 the cumulative risks of lung cancer by age 75 were 10%, 6%, 3%, and 2%.

CONCLUSIONS

People who stop smoking, even well into middle age, avoid most of their subsequent risk of lung cancer, and stopping before middle age avoids more than 90% of the risk attributable to tobacco. Mortality in the near future and throughout the first half of the 21st century could be substantially reduced by current smokers giving up the habit. In contrast, the extent to which young people henceforth become persistent smokers will affect mortality rates chiefly in the middle or second half of the 21st century.

The growth of Listeria monocytogenes in cheese packed under a modified atmosphere

The effect of modified atmosphere Packaging (MAP) on the growth of Listeria monocytogenes in mould ripened cheeses was studied at refrigeration temperatures (2-8.3 degrees C) over a storage period of 6 weeks. Control experiments in cling film with no atmospheric modification produced a lag time before growth of up to 1 week and rapid subsequent growth. MAP with a CO2 concentration of less than 20% allowed growth to occur but when O2 was incorporated; the lag time was reduced from 3 to 2 weeks and subsequent growth was also faster, producing an increase in cell numbers of 1.4 log cycles over the incubation period. N2-MAP in the absence of O2 increased the lag time to 3 weeks and slowed growth, while the inclusion of CO2 extended the lag to 3 weeks and slowed subsequent growth even more. In MAP with 80:10:10 (v/v/v) N2:CO2:O2, there was a lag period of 2-3 weeks before growth of L. monocytogenes occurred, while the total viable aerobic count (TVAC) decreased by 2-3 log cycles and the total Lactobacillus count showed little change. It was concluded that MAP was not suitable for preventing the growth of L. monocytogenes in such cheeses.

Gender differences in lung cancer risk by smoking: a multicentre case-control study in Germany and Italy

Several studies in the past have shown appreciably higher lung cancer risk estimates associated with smoking exposure among men than among women, while more recent studies in the USA report just the opposite. To evaluate this topic in a European population we conducted a case-control study of lung cancer in three German and three Italian centres. Personal interviews and standardized questionnaires were used to obtain detailed life-long smoking and occupational histories from 3723 male and 900 female cases and 4075 male and 1094 female controls. Lung cancer risk comparing ever-smokers with never-smokers was higher among men (odds ratios (OR) adjusted for age and centre = 16.1, 95% confidence interval (CI) 12.8-20.3) than among women (OR = 4.2, CI 3.5-5.1). Because the smoking habits of women were different from men, we conducted more detailed analyses using comparable levels of smoking exposure. After restriction to smokers and adjustment for other smoking variables, risk estimates did not differ appreciably between genders. The analysis of duration of smoking (0-19, 20-39, 40+ years) adjusted for cigarette consumption and time since quitting smoking revealed similar risk estimates in men (OR = 1.0, 3.3 [CI 2.6-4.2], 4.1 [CI 3.1-5.6]) and women (OR = 1.0, 2.7 [CI 1.7-4.1], 3.3 [CI 1.9-5.8]). The same was true of the analysis of average or cumulative smoking consumption, and also of analyses stratified by different histological types. We conclude that for comparable exposure to tobacco smoke, the risk of lung cancer is comparable in women and men.

The long-term effect of advice to eat more fish on blood pressure in men with coronary disease: results from the diet and reinfarction trial

BACKGROUND

Systematic reviews of fish and fish oil supplements have reported modest reductions in blood pressure (BP). Many of the trials included in these reviews used high doses of fish oil and most were of short duration.

METHOD

Between 1983 and 1987 2033 men under the age of 70, who had recently suffered a myocardial infarction, were enrolled in a 2-year trial of dietary advice-the Diet and Reinfarction Trial (DART). Participants were randomised in a factorial design to receive intensive advice to eat more fish, less fat or more fibre. Those men randomised to receive fish advice were encouraged to eat two portions of fatty fish each week. Intake of eicosapentaenoic acid was 0.33 g per day in the fish advice arm and 0.10 g per day in men not given fish advice.

RESULTS

The difference in systolic BP in the fish advice arm, adjusted for age and BP at baseline, was -0.61 mm Hg (95% CI -2.15, 0.92) at 6 months and 0.40 mm Hg (95% CI -1.33, 2.13) at 2 years. The difference in diastolic BP in the fish advice arm, adjusted for age and BP at baseline, was -0.50 mm Hg (95% CI -1.47, 0.46) at 6 months and 0.19 mm Hg (95% CI -0.88, 1.26) at 2 years.

CONCLUSIONS

Advice to eat modest amounts of fish has little effect on BP in men with coronary disease.

The effect of reproductive history on future pregnancy outcomes

The aim of this study was to examine the separate and joint effects of previous pregnancy history, year of pregnancy outcome, maternal age, height, smoking and fertility on risk of fetal death. Data were available from a study of female radiographers. Analyses were carried out on 3053 women with a total of 6993 pregnancies. Women reporting problems with conception or previous fetal losses had an increased risk of a pregnancy ending in a fetal death. In particular, women with primary or secondary infertility had an approximately fourfold increase in risk compared with women who reported no difficulties [odds ratio (OR): 3.92; 95% confidence interval (CI): (3.02, 5.07)]. This relationship was independent of pregnancy order and pregnancy history and was more marked in older maternal ages. The effect of pregnancy history was cumulative and possibly multiplicative in effect, with a threefold increase in the risk of losing a third pregnancy following two previous losses [OR: 3.19; 95% CI: (1.60, 6.35)]. There were no consistent patterns of risk associated with year of pregnancy outcome, maternal age, height or smoking status. These results suggest that previous pregnancy outcomes and problems with conception may be the strongest determinants of fetal loss in subsequent pregnancies.

Ecological study of social fragmentation, poverty, and suicide

OBJECTIVES

To investigate the association between suicide and area based measures of deprivation and social fragmentation.

DESIGN

Ecological study.

SETTING

633 parliamentary constituencies of Great Britain as defined in 1991.

MAIN OUTCOME MEASURES

Age and sex specific mortality rates for suicide and all other causes for 1981-92.

RESULTS

Mortality from suicide and all other causes increased with increasing Townsend deprivation score, social fragmentation score, and abstention from voting in all age and sex groups. Suicide mortality was most strongly related to social fragmentation, whereas deaths from other causes were more closely associated with Townsend score. Constituencies with absolute increases in social fragmentation and Townsend scores between 1981 and 1991 tended to have greater increases in suicide rates over the same period. The relation between change in social fragmentation and suicide was largely independent of Townsend score, whereas the association with Townsend score was generally reduced after adjustment for social fragmentation.

CONCLUSIONS

Suicide rates are more strongly associated with measures of social fragmentation than with poverty at a constituency level.

Graphical trees: the simultaneous display of risk of fetal death by pregnancy history and maternal age

Many epidemiological studies consider sequences of events over time where the outcome of interest is determined, at least in part, by similar outcomes that have occurred in the past, e.g. risk of fetal death in successive pregnancies. In this situation, a probability tree can provide useful insights into the relationship between successive events. However, probability trees are usually limited to the display of a single variable, whereas the majority of studies also include other risk factors. Analyses involving other factors, particularly those that consider interactions, can produce an abundance of results that make identification of potentially interesting patterns difficult. A new graphical approach is described for simultaneously presenting the effects of two risk factors where one relates to a sequence of events over time. The graphical tree highlights patterns in the raw data and is therefore proposed for use in exploratory analyses and hypothesis generation. The approach is introduced and illustrated in the context of risk factors for fetal death, and an interaction between pregnancy history and maternal age is explored.

Some aspects of measurement error in explanatory variables for continuous and binary regression models

A simple form of measurement error model for explanatory variables is studied incorporating classical and Berkson cases as particular forms, and allowing for either additive or multiplicative errors. The work is motivated by epidemiological problems, and therefore consideration is given not only to continuous response variables but also to logistic regression models. The possibility that different individuals in a study have errors of different types is also considered. The relatively simple estimation procedures proposed for use with cohort data and case-control data are checked by simulation, under the assumption of various error structures. The results show that even in situations where conventional analysis yields slope estimates that are on average attenuated by a factor of approximately 50 per cent, estimates obtained using the proposed amended likelihood functions are within 5 per cent of their true values. The work was carried out to provide a method for the analysis of lung cancer risk following residential radon exposure, but it should be applicable to a wide variety of situations.