Environmental mismatch and obesity in humans: The Jerusalem Perinatal Family Follow-Up Study.

BACKGROUND: According to the hypothesis of Gluckman and Hanson, mismatch between the developmental and postdevelopmental environments may lead to detrimental health impacts such as obesity. While several animal studies support the mismatch theory, there is a scarcity of evidence from human-based studies. OBJECTIVES: Our study aims to examine whether a mismatch between the developmental and young-adult environments affect obesity in young adults of the Jerusalem Perinatal Family Follow-Up Study. METHODS: Data from The Jerusalem Perinatal Family Follow-Up Study birth cohort was used to characterize early and late environments using offspring and parental sociodemographic and lifestyle information at birth, age 32 (n = 1140) and 42 (n = 404). Scores characterizing the early and late environments were constructed using factor analysis. To assess associations of mismatch with obesity, regression models were fitted using the first factor of each environment and adiposity measures at age 32 and 42. RESULTS: Having a stable non-beneficial environment at birth and young-adulthood was most strongly associated with increased adiposity, while a stable beneficial environment was most favorable. The transition from a beneficial environment at birth to a less beneficial environment at young-adulthood was associated with higher obesity measures, including higher BMI (ß = 0.979; 95% CI: 0.029, 1.929), waist circumference (ß = 2.729; 95% CI: 0.317, 5.140) and waist-hip ratio (ß = 0.017; 95% CI: 0.004, 0.029) compared with those experiencing a beneficial environment at both time points. Transition from a less beneficial environment at birth to a beneficial environment at adulthood was also associated with higher obesity measurements (BMI -ß = 1.116; 95% CI: 0.085, 2.148; waist circumference -ß = 2.736; 95% CI: 0.215, 5.256). CONCLUSIONS: This study provides some support for the mismatch hypothesis. While there is indication that an accumulation of the effects of the non-beneficial environment has the strongest detrimental impact on obesity outcomes, our results also indicate that a mismatch between the developmental and later environments may result in maladaptation of the individual leading to obesity.

Habitual sleep duration and sleep duration variation are independently associated with body mass index.

BACKGROUND: Sleep plays a vital role in maintaining homeostasis and promoting health. Previous studies show that shorter sleep duration is associated with elevated body mass index (BMI) and other cardiovascular risk factors. The goal of this study was to investigate the effects of habitual sleep duration and nightly sleep duration variation based on daily device-recorded data on BMI and obesity-related biomarkers. METHODS: In all, 748 individuals (50.6% females, 85.4% European-Americans, average age: 49.7 years old) participated in a commercial lifestyle coaching program beginning in July 2015. Daily sleep data were recorded by Fitbit Charge HR wristbands. Clinical laboratory blood tests were measured up to three times over a 12-month period. Linear regression models were used for cross-sectional analyses, and generalized estimating equations for longitudinal analyses. All models were adjusted for age, sex, geographic location, season, genetic ancestry inferred from whole genome sequencing data, and BMI (if applicable). Multiple testing issues were corrected by false discovery rate. RESULTS: We calculated habitual sleep duration and nightly sleep duration variation. In general, females slept 15-min longer on average than males. A negative correlation was found between habitual sleep duration and BMI (ß=-1.12, standard error=0.25, P<0.001). Moreover, we identified a positive correlation between sleep duration variation and BMI (ß=2.97, standard error=0.79, P<0.001) while controlling for sleep duration, indicating that larger sleep duration variation is significantly and independently associated with increased BMI. CONCLUSIONS: We explored the impact of habitual sleep duration and sleep duration variation, and identified that shorter habitual sleep duration and larger duration variation were independently associated with increased BMI.

Live birth sex ratios and father's geographic origins in Jerusalem, 1964-1976.

OBJECTIVE: To examine whether ancestry influenced sex ratios of offspring in a birth cohort before parental antenatal sex selection influenced offspring sex. METHODS: We measured the sex ratio as the percent of males according to countries of birth of paternal and maternal grandfathers in 91,459 live births from 1964 to 1976 in the Jerusalem Perinatal Study. Confidence limits (CI) were computed based on an expected sex ratio of 1.05, which is 51.4% male. RESULTS: Of all live births recorded, 51.4% were male. Relative to Jewish ancestry (51.4% males), significantly more males (1,761) were born to Muslim ancestry (54.5, 95% CI = 52.1-56.8, P = 0.01). Among the former, sex ratios were not significantly associated with paternal or maternal age, education, or offspring's birth order. Consistent with a preference for male offspring, the sex ratio decreased despite increasing numbers of births over the 13-year period. Sex ratios were not affected by maternal or paternal origins in North Africa or Europe. However, the offspring whose paternal grandfathers were born in Western Asia included fewer males than expected (50.7, 50.1-51.3, P = 0.02), whether the father was born abroad (50.7) or in Israel (50.8). This was observed for descendents of paternal grandfathers born in Lebanon (47.6), Turkey (49.9), Yemen & Aden (50.2), Iraq (50.5), Afghanistan (50.5), Syria (50.6), and Cyprus (50.7); but not for those from India (51.5) or Iran (51.9). The West Asian group showed the strongest decline in sex ratios with increasing paternal family size. CONCLUSIONS: A decreased sex ratio associated with ancestry in Western Asia is consistent with reduced ability to bear sons by a subset of Jewish men in the Jerusalem cohort. Lower sex ratios may be because of pregnancy stress, which may be higher in this subgroup. Alternatively, a degrading Y chromosome haplogroup or other genetic or epigenetic differences on male germ lines could affect birth ratios, such as differential exposure to an environmental agent, dietary differences, or stress. Differential stopping behaviors that favor additional pregnancies following the birth of a daughter might exacerbate these lower sex ratios.

Long-term efficacy of Paula method as compared with pelvic floor muscle training for stress urinary incontinence in women: a 6-month follow-up.

PURPOSE: The purpose of this study was to examine the long-term efficacy of an exercise regimen based on circular muscle strengthening (Paula method) as opposed to pelvic floor muscle training (PFMT) on stress urinary incontinence symptoms at 6 months postintervention. SUBJECTS AND SETTING: Of 240 women who had initially participated in a randomized clinical trial, 143 women suffering from stress urinary incontinence participated in this follow-up study. METHODS: Subjects participated in a randomized controlled clinical trial comparing 2 exercise programs (12 private Paula lessons vs 6 group PFMT lessons) over a 12-week period. Of these, 143 women took part in the follow-up study: 64 from the Paula group and 79 from the PFMT group. Six-month follow-up data were gathered via telephone interviews. RESULTS: No significant deterioration in stress urinary incontinence symptoms occurred 6 months after completion of the interventions in either group. We found a statistically significant difference between the groups with regard to reported frequency of urinary leakage; 25 of subjects (39.7%) allocated to the Paula method reported a low frequency rate of incontinence episodes upon completion of the study as compared to 18 (22.8%) in the PFMT group (P = .03). Forty-nine of the 64 women in the Paula group (76.6%) and 62 of the 79 women in the PFMT group (78.5%) reported that they continued exercising 6 months after completion of the trial (P = .8). CONCLUSIONS: Both intervention methods reduced frequency of urinary incontinence over a 6-month period. Long-term adherence was similar in both groups. Pelvic floor muscle training was associated with fewer sessions and decreased cost and fewer lessons needed as compared with the Paula method. Nevertheless, results also suggest that the Paula method achieves a lower frequency of urinary leakage than PFMT.

Cancer risk after exposure to treatments for ovulation induction.

Uncertainty continues as to whether treatments for ovulation induction are associated with increased risk of cancer. The authors conducted a long-term population-based historical cohort study of parous women. A total of 15,030 women in the Jerusalem Perinatal Study who gave birth in 1974-1976 participated in a postpartum survey. Cancer incidence through 2004 was analyzed using Cox's proportional hazards models, controlling for age and other covariates. Women who used drugs to induce ovulation (n = 567) had increased risks of cancer at any site (multivariate hazard ratio (HR) = 1.36, 95% confidence interval (CI): 1.06, 1.74). An increased risk of uterine cancer was found among women treated with ovulation-inducing agents (HR = 3.39, 95% CI: 1.28, 8.97), specifically clomiphene (HR = 4.56, 95% CI: 1.56, 13.34). No association was noted between use of ovulation-inducing agents and ovarian cancer (age-adjusted HR = 0.61, 95% CI: 0.08, 4.42). Ovulation induction was associated with a borderline-significant increased risk of breast cancer (multivariate HR = 1.42, 95% CI: 0.99, 2.05). Increased risks were also observed for malignant melanoma and non-Hodgkin lymphoma. These associations appeared stronger among women who waited more than 1 year to conceive. Additional follow-up studies assessing these associations by drug type, dosage, and duration are needed.

Consanguinity and birth defects in the jerusalem perinatal study cohort.

BACKGROUND: While parental consanguinity is known to increase the risk of birth defects in offspring, it is hard to quantify this risk in populations where consanguinity is prevalent. METHODS: To support ongoing studies of cancer and of psychiatric disease, we studied relationships of consanguinity to 1,053 major birth defects in 29,815 offspring, born in 1964-1976. To adjust for confounding variables (geographic origin, social class and hospital), we constructed logistic regression models, using GEE to take into account correlations between sibs. Odds ratios (ORs) and 95% confidence limits were estimated in comparison to a reference group of offspring with grandfathers born in different countries. RESULTS: With 10.1% of offspring having consanguineous parents, the adjusted OR for major birth defect was 1.41 (1.12-1.74). Offspring of marriages between uncles-nieces, first cousins and more distant relatives showed adjusted ORs of 2.36 (0.98-5.68), 1.59 (1.22-2.07) and 1.20 (0.89-1.59) respectively. For descendents of grandfathers born in the same country, but not known to be related, the OR was 1.05 (0.91-1.21); these showed increased risk associated with ancestries in Western Asia (1.27, 1.04-1.55, p < 0.02) or Europe (1.13, 0.79-1.80). CONCLUSIONS: A strong association of consanguinity with poverty and low education points to the need to avoid exposure to environmental hazards in these families.

Twin pregnancy and the risk of schizophrenia.

BACKGROUND: Twins are exposed to intrauterine environments that differ significantly from those of singletons. These diverse environments might alter the risk for schizophrenia in twins and make it difficult to generalize from findings in twins when studying the risk of schizophrenia in the general population. Previous studies report contradictory findings on the risk for schizophrenia in twins. METHODS: We studied the incidence of schizophrenia spectrum disorders, ascertained from Israel's National Psychiatric Registry, in a cohort of 2124 twins and 87,955 singletons. These offspring were followed from their birth in 1964-76 in the Jerusalem Perinatal study. Cox proportional hazards methods were used to compare outcomes over 28-41 years, adjusting for ages of parents. RESULTS: Twins showed a relative risk [RR] of .84 relative to singletons, with a 95% confidence interval [CI] of (.51-1.4). RRs and CIs for males and females were .68 [.34-1.4] and 1.1 [.55-2.2] respectively. Twins in male-male, female-female or opposite-sex sets showed no significant variation in RRs; furthermore, first- or second-born twins did not differ significantly from each other. Siblings of twins had the same risk of schizophrenia as siblings of singletons. CONCLUSION: Twins have the same risk for schizophrenia as the general population.

Television viewing and obesity: a prospective study in the 1958 British birth cohort.

OBJECTIVE: To assess whether frequency of television viewing in adolescence (11 and 16 years) or early adulthood (23 years) affected subsequent changes in body mass index (BMI) through to mid-adulthood life, and waist-hip ratio in mid-adulthood. SUBJECTS: The 1958 British birth cohort includes all births in 1 week in March 1958 in England, Scotland and Wales. The main analyses included at least 11 301 participants. Outcome measures included BMI at 16, 23, 33 and 45 years and waist-hip ratio at 45 years. RESULTS: Watching television 'often' at 16 years (but not 11 years) was associated with a faster gain in BMI between 16 and 45 years in males (0.011 kg m(-2) per year, 95% confidence interval (CI) 0.003, 0.019) and females (0.013 kg m(-2) per year, 95%CI 0.003, 0.023). More frequent television viewing at 11, 16 and 23 years was associated with a faster gain in BMI between 23 and 45 years in females, but not in males. Television viewing at 23 years was associated with waist-hip ratio at 45 years: participants watching > or = 5 times per week had a waist-hip ratio 0.01 higher than those watching less often. At 45 years, those watching television for > or = 4 h day(-1) had a waist-hip ratio 0.03-0.04 higher than those watching for <1 h day(-1). CONCLUSIONS: More frequent television viewing in adolescence and early adulthood is associated with greater BMI gains through to mid-adulthood and with central adiposity in mid-life. Television viewing may be a useful behaviour to target in strategies to prevent obesity.

Effect of non-homogeneous surface viscosity on the Marangoni migration of a droplet in viscous fluid.

Marangoni migration of a single droplet in an unbounded viscous fluid under the additional effect of variable surface viscosity is studied. The surface tension and the surface viscosity depend on concentration of dissolved species. Cases of the motion induced by the presence of a point source and by a given constant concentration gradient are considered. The dependence of the migration velocity on the governing parameters is computed under quasi-stationary approximation. The effect of weak advective transport is studied making use of singular perturbations in the Peclet number, Pe. It is shown that, when the source is time dependent a Basset-type history term appears in the expansion of the concentration and, as a result, the leading order correction to the flow and to the migration velocity is of O(Pe(1/2)). If the source of active substance driving the flow is steady, the effect of convective transport on the migration is weaker.

A prospective, randomised study comparing the percutaneous compression plate and the compression hip screw for the treatment of intertrochanteric fractures of the hip.

Limited access surgery is thought to reduce post-operative morbidity and provide faster recovery of function. The percutaneous compression plate (PCCP) is a recently introduced device for the fixation of intertrochanteric fractures with minimal exposure. It has several potential mechanical advantages over the conventional compression hip screw (CHS). Our aim in this prospective, randomised, controlled study was to compare the outcome of patients operated on using these two devices. We randomised 104 patients with intertrochanteric fractures (AO/OTA 31.A1-A2) to surgical treatment with either the PCCP or CHS and followed them for one year postoperatively. The mean operating blood loss was 161.0 ml (8 to 450) in the PCCP group and 374.0 ml (11 to 980) in the CHS group (Student's t-test, p < 0.0001). The pain score and ability to bear weight were significantly better in the PCCP group at six weeks post-operatively. Analysis of the radiographs in a proportion of the patients revealed a reduced amount of medial displacement in the PCCP group (two patients, 4%) compared with the CHS group (10 patients, 18.9%); Fisher's exact test, p < 0.02. The PCCP device was associated with reduced intra-operative blood loss, less postoperative pain and a reduced incidence of collapse of the fracture.

Associations of socioeconomic position in childhood and young adulthood with cardiometabolic risk factors: the Jerusalem Perinatal Family Follow-Up Study.

BACKGROUND: Several stages in the life course have been identified as important to the development of cardiovascular disease. This study aimed to assess the associations of childhood and adulthood socioeconomic position (SEP) and social mobility with cardiometabolic risk factors (CMRs) later in life. METHODS: We conducted follow-up examinations of 1132 offspring, aged 32, within a population-based cohort of all births in Jerusalem from 1974 to 1976. SEP was indicated by parents' occupation and education, and adulthood SEP was based on offspring's occupation and education recorded at age 32. Linear regression models were used to investigate the associations of SEP and social mobility with CMRs. RESULTS: Childhood-occupational SEP was negatively associated with body mass index (BMI; ß=-0.29, p=0.031), fat percentage (fat%; ß=-0.58, p=0.005), insulin (ß=-0.01, p=0.031), triglycerides (ß=-0.02, p=0.024) and low-density lipoprotein cholesterol (LDL-C; ß=-1.91, p=0.015), independent of adulthood SEP. Adulthood-occupational SEP was negatively associated with waist-to-hip ratio (WHR; ß=-0.01, p=0.002), and positively with high-density lipoprotein cholesterol (HDL-C; ß=0.87, p=0.030). Results remained similar after adjustment for smoking and inactivity. Childhood-educational SEP was associated with decreased WHR and LDL-C level (p=0.0002), and adulthood-educational SEP was inversely associated with BMI (p=0.001), waist circumference (p=0.008), WHR (p=0.001) and fat% (p=0.0002) and positively associated with HDL-C (p=0.030). Additionally, social mobility (mainly upward) was shown to have adverse cardiometabolic outcomes. CONCLUSIONS: Both childhood and adulthood SEP contribute independently to CMR. The match-mismatch hypothesis may explain the elevated CMRs among participants experiencing social mobility. Identification of life-course SEP-related aspects that translate into social inequality in cardiovascular risk may facilitate efforts for improving health and for reducing disparities in cardiovascular disease.

Does one's own and one's spouse's education affect overall and cause-specific mortality in the elderly?

OBJECTIVES: To examine educational gradients in overall and cause-specific mortality among elderly married men and women and their spouses. METHODS: Using the census-based Israel Longitudinal Mortality Study (1983-92), 13 573 married men and 6563 married women were identified who were aged 70-89 years at baseline. Cox proportional hazard models were used to assess the strength of the association between education and overall and cause-specific mortality. RESULTS: Educational gradients for own and spouse's mortality varied by gender and cause of death. In particular, in relation to cardiovascular disease, men married to uneducated wives experienced elevated mortality risks [hazard ratio (HR) = 1.30; 95% confidence interval (95% CI) 1.11-1.52]. Women were generally unaffected by their husband's education, except for those who died from non-breast cancer, for whom husband's low education had a harmful effect (HR = 1.98; 95% CI 1.26-3.11). CONCLUSIONS: Mortality among elderly married persons is associated with one's own and one's spouse's educational achievement. Research using partner's education as a proxy for one's own attainment may be omitting valuable information regarding these and other health risks.

Adolescent drinking level and adult binge drinking in a national birth cohort.

AIMS: To assess (i) continuities in binge drinking across adulthood and (ii) the association between adolescent drinking level and adult binge drinking. DESIGN: Population-based prospective birth cohort. SETTING: England, Scotland and Wales. PARTICIPANTS: All births during one week in March 1958 (n = 8520 in analysis). MEASUREMENTS: Alcohol consumption reported at 16, 23, 33 and 42 years. Binge drinkers were identified by dividing number of units of alcohol consumed in the last week by usual drinking frequency, with limits of >/=10 units/occasion for men and >/=7 for women. FINDINGS: Four in five cohort members drank alcohol at least twice a month. Prevalences of binge drinking at 23, 33 and 42 years among men were 37%, 28% and 31% and among women 18%, 13% and 14%. Most binge drinkers in adulthood changed drinking status during this period. Nevertheless, binge drinking at age 23 increased the odds of binge drinking at 42 years: odds ratio (OR) 2.10 (95% CI 1.85, 2.39) for men; OR 1.56 (95% CI 1.29,1.89) for women. Women who rarely or never drank aged 16 were less likely than light drinkers (0-2 units/week) to binge drink as adults, OR at 23 years 0.65 (95% CI 0.55, 0.77). Men who were heavier drinkers (>/=7 units/week) at 16 years were more likely than light drinkers to binge drink throughout adulthood; at 42 years, OR 1.64 (95% CI 1.33, 2.08). CONCLUSIONS: Binge drinking is common in British men and women throughout adulthood with continuities between the 20s and 40s. Adolescent drinking has a modest although important association with adult binge drinking.

Changes in diet and physical activity in the 1990s in a large British sample (1958 birth cohort).

OBJECTIVES: To investigate whether adults studied in 1991 and 1999 (at ages 33 and 42 y) improved their diet and their physical activity level, in the direction of recommendations issued during the same period. DESIGN: Longitudinal 1958 British birth cohort study. SETTING: England, Scotland and Wales. PARTICIPANTS: All births, 3rd-9th March, 1958. A minimum of 11 341 participants provided data at 33 y, 11 361 at 42 y. MAIN OUTCOME MEASURES: Frequency of leisure time activity and consumption of (i) fried food, (ii) chips, (iii) wholemeal bread and (iv) fruit and salad/raw vegetables, at 33 and 42 y. RESULTS: Most people changed their physical activity and dietary habits over the 8-y period. About a third of men and women increased, and a third decreased their activity frequency. Findings for fried food consumption were similar. A significantly greater proportion of cohort members decreased their chips consumption (32%), rather than increased it (17%) and increased their fruit and salad consumption (30%), rather than decreased it (25%). In all, 26% of men and 33% of women consistently ate, or switched to eating mostly wholemeal bread, while 56% of men and 48% of women consistently ate less or switched to eating less. Social gradients were seen for activity and diet in 1991, but associations between social factors or body mass index and change in activity or diet were inconsistent. CONCLUSIONS: Lifestyle habits such as dietary intake and physical activity are slow to change. Current health promotion strategies may need to be supplemented with additional methods to affect the desired change in these habits.

Stability of red blood cell membrane fatty acid composition after acute myocardial infarction.

Questionnaire-based assessment of dietary intake may be invalidated in case-control studies by biases of recall, reporting or interviewing. Biomarkers, free of such biases, can be useful adjunct measures if they themselves are not affected by the event under investigation. Consequently, we studied the stability of the fatty acid composition of the red blood cell (RBC) membrane during a 1-week period, in 20 patients aged 40-74 years after an acute myocardial infarction (MI). Statistical analysis that accounted for a repeated measures design with missing data was undertaken for five fatty acids: C16:0, C18:1, C18:2, C20:5 and C22:6. All fatty acids showed change over the 7 day period. Individuals tended to maintain their relative ranking over time as reflected by correlations between time points of between 0.85 to 0.90, with the exception of C16:0 in which correlations were lower and inconsistent. Over the first 24 hr from admission all fatty acids except C20:5 showed evidence of a statistically significant change. However over the first 7 hr C18:1, C18:2, C20:5 and C22:6 exhibited stability whereas C16:0 altered. We conclude that the fatty acid composition of the RBC membrane appears to change soon after an acute MI. Consequently, case-control studies may be biased towards positive associations for C16:0 and inverse associations for C18:2 and C20:5, i.e. consistent with conventional predictions. However, if blood samples are drawn within 6 hr of admission, bias in estimation of C18:1, C18:2, C20:5 and C22:6 may be unimportant.

A prospective study of limiting longstanding illness in early adulthood.

BACKGROUND: Chronic illness and disability are of increasing public health importance but little is known about the lifetime influences involved in their onset and progression. We aim to (i) establish whether an individual's rating of limiting illness is stable over a 10-year period from age 23 to 33; (ii) assess the relationship between childhood and adult disability; and (iii) identify lifecourse influences on limiting illness in early adulthood. METHODS: Data were from the 1958 British birth cohort, including the original birth survey and follow-ups at ages 7, 11, 16, 23 and 33 years. Limiting longstanding illness was the outcome at both ages 23 and 33. Potential predictors included childhood health and physical development, socioeconomic conditions in early life and adulthood, and behavioural factors. We estimated the effect of potential explanatory factors using logistic regression, in both univariate and multivariate analyses, separately for limiting illness at 23 and 33 years. RESULTS: Prevalence of limiting illness increased from 5.1% (men) and 4.1% (women) at age 23 to 6% for both sexes at age 33. Risk of limiting illness at age 33 was greater for those reporting an illness at age 23 (29.4%, compared with 4.7% of those without illness), though the majority (66%) of 33-year limiting illnesses had no previous record at age 23 or for childhood. Multivariate analysis of limiting illness at age 23 confirmed the high risk for those with childhood disability and also established two further major predictors, namely, injury (adjusted odds ratio [OR] = 1.42, 95% CI: 1.09-1.86) and intermediate socio-emotional status (adjusted OR = 1.73, 95% CI: 1.29-2.31). Additional risks were identified for limiting illness at age 33, including: (i) injury in the preceding 10 years (adjusted OR = 1.55, 95% CI : 1.18-2.04); (ii) body mass index (BMI), for which the relationship was non-linear, with elevated risks for the underweight (adjusted OR = 1.53, 95% CI: 1.03-2.26) and overweight (OR = 1.28, 95% CI: 0.87-1.89); (iii) childhood disadvantage at either or both ages 7 and 11 (adjusted OR = 1.53, 95% CI : 1.07-2.17); and (iv) height at age 7, with a significant non-linear relationship (the adjusted OR for height less than 15th percentile was 1.43 and for height more than the 85th percentile, 1.30). CONCLUSIONS: Both childhood and adult factors predict limiting illness in early adulthood. Childhood is important because some adult illnesses originate in early life, and also because childhood environment influences the risk of adult limiting illness several years later. Our findings suggest that studies seeking to understand the causes of limiting illness, that currently tend to focus exclusively on contemporary factors, need also to consider the contribution of environment in early life.

Dichotomous or categorical response? Analysing self-rated health and lifetime social class.

BACKGROUND: Self-rated health is a commonly used measure of health status, usually having three to five categories. The measure is often collapsed into a dichotomous variable of good versus less than good health. This categorization has not yet been justified. METHODS: Using data from the 1958 British birth cohort, we examined the relationship between socioeconomic conditions, indicated by occupational class at four ages, and self-rated health. Results obtained for a dichotomous variable using logistic regression were compared with alternative methods for ordered categorical variables including polytomous regression, cumulative odds, continuation ratio and adjacent categories models. RESULTS AND CONCLUSIONS: Findings concerning the relationship between socioeconomic position and self-rated health yielded by a logistic regression model were confirmed by alternative statistical methods which incorporate the ordered nature of self-rated health. Similarity of results was found regarding size and significance of main effects, type of association and interactive effects.

Self-rated health and limiting longstanding illness: inter-relationships with morbidity in early adulthood.

BACKGROUND: Self-rated health and limiting longstanding illness are both widely used global measures of health, but understanding is poor of their meaning and validity at younger ages. METHODS: We examined the association between self-rated health and limiting longstanding illness and specific health problems at two ages (23 and 33 years), and assessed change over the 10-year period for each health measure relative to another. Longitudinal data were taken from the nationally representative British birth cohort for which health measures were obtained at ages 23 and 33. RESULTS: Self-rated health and limiting longstanding illness were strongly associated with each other as well as with specific health problems, particularly with serious conditions (e.g. epilepsy, cancer, diabetes) and more weakly with less serious conditions (e.g. eczema and hay fever). Rating of overall health and limiting longstanding illness was highly stable during the 10-year period with most, but not all, health change reflecting a deterioration in health status. Deterioration in limiting illness corresponded to an even greater health decline in specific conditions. CONCLUSIONS: Self-rated health and limiting longstanding illness are valid health measures appropriate for use in general health surveys.

Probabilistic reasoning and clinical decision-making: do doctors overestimate diagnostic probabilities?

BACKGROUND: The "threshold approach" is based on a physician's assessment of the likelihood of a disease expressed as a probability. The use of Bayes' theorem to calculate disease probability in patients with and without a particular characteristic, may be hampered by the presence of subadditivity (i.e. the sum of probabilities concerning a single case scenario exceeding 100%). AIM: To assess the presence of subadditivity in physicians' estimations of probabilities and the degree of concordance among doctors in their probability assessments. DESIGN: Prospective questionnaire. METHODS: Residents and trained physicians in Family Medicine, Internal Medicine and Cardiology (n = 84) were asked to estimate the probability of each component of the differential diagnosis in a case scenario describing a patient with chest pain. RESULTS: Subadditivity was exhibited in 65% of the participants. The total sum of probabilities given by each participant ranged from 44% to 290% (mean 137%). There was wide variability in the assignment of probabilities for each diagnostic possibility (SD 16-21%). DISCUSSION: The finding of substantial subadditivity, coupled with the marked discordance in probability estimates, questions the applicability of the threshold approach. Physicians need guidance, explicit tools and formal training in probability estimation to optimize the use of this approach in clinical practice.

Do spermatozoa secrete motility enhancing factor?

OBJECTIVES: To determine whether medium conditioned with human spermatozoa was capable of enhancing sperm motility and penetration ability. DESIGN: Paired aliquots of washed spermatozoa were allowed to incubate for nine different incubation periods, ranging from 15 to 240 minutes in 37 degrees C in humidified atmosphere with 5% CO2. After this, they were centrifuged at 600 x g for 6 minutes. The conditioned medium was removed from one tube of each pair and replaced with fresh medium. In the other tube of the same pair the sperm pellet was resuspended in the same medium. In a second set of experiments, conditioned medium was removed from tubes containing samples of spermatozoa after different predefined incubation periods. This was used to replace medium that had been removed from sperm cells that had been incubated for 120 minutes. Motility and penetration of zona-free hamster eggs were assessed. RESULTS: Removal of the incubation medium at times between 15 to 240 minutes resulted in sperm that showed a gradual decrease in motility and penetration ability followed by a gradual increase in motility and penetration ability, i.e., an inverted bell-shaped effect. The addition of conditioned medium obtained after different periods of incubation to spermatozoa where medium was removed after 120 minutes of incubation resulted in an increase in sperm motility and penetration ability. The longer the medium was conditioned with spermatozoa the more prominent the effect on sperm motility and penetration ability, with maximal effect observed with medium conditioned for 120 minutes. CONCLUSIONS: Medium conditioned with human spermatozoa enhances sperm motility and penetration ability.