Notified occupational mental disorders: associations with health and income.

BACKGROUND: Studies indicate that workers' compensation claim processes may affect patients' health negatively. However, few studies focus on patients with mental health claims, and the claim process varies between countries. AIMS: The aims of this study were to examine whether being notified to the Danish Labour Market Insurance with an occupational mental health condition was associated with changes in visits to the general practitioner (GP), use of medicine and annual income. METHODS: Study participants were 965 patients with a mental disorder examined at a department of occupational medicine. Of these, 669 patients were notified with an occupational mental disorder, 296 were not. Health-related outcomes, including GP visits and prescriptions of psychotropic drugs, were estimated at baseline during the year of medical examination, while annual income was estimated a year before the examination. The follow-up was the year after the year of examination for all outcomes. Outcomes were collected from the Danish National Bureau of Statistics. Analyses were conducted using Poisson regression and conditional logistic regression. RESULTS: All measured outcomes decreased from baseline to follow-up in both groups. These changes were not significantly different depending on notification status at baseline. CONCLUSIONS: This study suggests that being notified with an occupational mental disorder does not significantly affect health-related outcomes. A significant decrease in annual income over time was seen in both groups, the notified and the unnotified group, highlighting the importance of providing support to all employees with a mental disorder.

Is aberrant affective cognition an endophenotype for affective disorders? - A monozygotic twin study.

BACKGROUND: Identification of endophenotypes can improve prevention, detection and development of new treatments. We therefore investigated whether aberrant affective cognition constitutes an endophenotype for affective disorders by being present in monozygotic (MZ) twins with unipolar or bipolar disorder in partial remission (i.e. affected) and their unaffected co-twins (i.e. high-risk) relative to twins with no family history of affective disorder (i.e. low-risk). METHODS: We conducted an assessor blind cross-sectional study from 2014 to 2017 of MZ twins using Danish population-based registers in recruitment. Twins attended one test session involving neurocognitive testing, clinical ratings and questionnaires. Main outcomes were attention to and recognition of emotional facial expressions, the memory of emotional self-referential words, emotion regulation and coping strategies. RESULTS: Participants were 103 affected, 44 high-risk and 36 low-risk MZ twins. Groups were demographically well-balanced and showed comparable non-affective cognitive performance. We observed no aberrant affective cognition in affected and high-risk relative to low-risk twins. However, high-risk twins displayed attentional avoidance of emotional faces (ps ⩽ 0.009) and more use of task-oriented coping strategies (p = 0.01) compared with affected twins. In contrast did affected twins show more emotion-oriented coping than high- and low-risk twins (ps ⩽ 0.004). CONCLUSIONS: Our findings provide no support of aberrant affective cognition as an endophenotype for affective disorders. High-risk twins' attentional avoidance of emotional faces and greater use of task-oriented coping strategies may reflect compensatory mechanisms.

Can doping graphite trigger room temperature superconductivity? Evidence for granular high-temperature superconductivity in water-treated graphite powder.

Granular superconductivity in powders of small graphite grains (several tens of micrometers) is demonstrated after treatment with pure water. The temperature, magnetic field and time dependence of the magnetic moment of the treated graphite powder provides evidence for the existence of superconducting vortices with some similarities to high-temperature granular superconducting oxides but even at temperatures above 300 K. Room temperature superconductivity in doped graphite or at its interfaces appears to be possible.

Explained variation in a fully specified model for data-grouped survival data.

An additive hazards model may be used to quantify the effect of genetic and environmental predictors on flowering of sugar beet plants recorded as data-grouped time-to-event data. Estimated predictor effects have an intuitive interpretation rooted in the underlying time dynamics of the flowering process. However, agricultural experiments are often designed using several plots containing a large number of plants that are subsequently being monitored. In this article, we consider an additive hazards model with an additional plot structure induced by latent shared frailty variables. This approach enables us to derive a method to assess the quality of predictors in terms of how much plot variation they explain. We apply the method to a large data set exploring flowering of sugar beet and conclude that the genetic predictor biotype, which has a strong effect, also explains a substantial amount of the plot variation. The method is also applied to a data set from medical research concerning days to virus positivity of serum samples in AIDS patients.

Fetal growth between the first and second trimesters and the risk of adverse pregnancy outcome.

OBJECTIVES: To relate growth rate of the biparietal diameter (BPD) between the first and second trimesters to the risk of perinatal death, intrauterine growth restriction (IUGR), macrosomia, preterm/post-term delivery and pre-eclampsia. METHODS: In this retrospective study, we analyzed sonographic BPD measurements at 11-14 and 17-21 weeks from 8215 singleton pregnancies in the Copenhagen First Trimester Study. Growth rate was defined as millimeters of growth per day between the two measurements and was dichotomized into growth rates < 2.5(th) vs. 2.5(th)-97.5(th) centiles, and > 97.5(th) vs. 2.5(th)-97.5(th) centiles. Odds ratios (OR) and 95% CIs for adverse outcome were calculated. RESULTS: Fetuses with growth rates < 2.5(th) centile had an OR of 4.79 (95% CI, 1.43-15.99) for perinatal death and an OR of 2.64 (95% CI, 1.51-4.62) for birth weight < sonographically estimated mean fetal weight (adjusted for gestational age) - 2 SD. Fetuses with growth rates > 97.5(th) centile had an OR of 2.83 (95% CI, 1.58-5.06) for birth weight > mean + 2 SD and an OR of 2.30 (95% CI, 1.15-4.59) for delivery in weeks 34-36. Growth rate showed no association with pre-eclampsia. CONCLUSIONS: There is a significant relationship between the growth rate of BPD from the first to the second trimester and adverse pregnancy outcome. Low growth rates are associated with an increased OR for perinatal death and IUGR, while high growth rates are associated with an increased OR for macrosomia and preterm delivery.

Ambient air pollution triggers wheezing symptoms in infants.

BACKGROUND: There is limited evidence for the role of air pollution in the development and triggering of wheezing symptoms in young children. A study was undertaken to examine the effect of exposure to air pollution on wheezing symptoms in children under the age of 3 years with genetic susceptibility to asthma. METHODS: Daily recordings of symptoms were obtained for 205 children participating in the birth cohort study Copenhagen Prospective Study on Asthma in Children and living in Copenhagen for the first 3 years of life. Daily air pollution levels for particulate matter <10 microm in diameter (PM(10)) and the concentrations of ultrafine particles, nitrogen dioxide (NO(2)), nitrogen oxide (NO(x)) and carbon monoxide (CO) were available from a central background monitoring station in Copenhagen. The association between incident wheezing symptoms and air pollution on the concurrent and previous 4 days was estimated by a logistic regression model (generalised estimating equation) controlling for temperature, season, gender, age, exposure to smoking and paternal history of asthma. RESULTS: Significant positive associations were found between concentrations of PM(10), NO(2), NO(x), CO and wheezing symptoms in infants (aged 0-1 year) with a delay of 3-4 days. Only the traffic-related gases (NO(2), NO(x)) showed significant effects throughout the 3 years of life, albeit attenuating after the age of 1 year. CONCLUSIONS: Air pollution related to traffic is significantly associated with triggering of wheezing symptoms in the first 3 years of life.

Size distribution and total number concentration of ultrafine and accumulation mode particles and hospital admissions in children and the elderly in Copenhagen, Denmark.

OBJECTIVES: To study the association between short-term exposure to ultrafine particles and morbidity in Copenhagen, Denmark. METHODS: We studied the association between urban background levels of the total number concentration of particles (NC(tot), 6-700 nm in diameter) measured at a single site (15 May 2001 to 31 December 2004) and hospital admissions due to cardiovascular (CVD) and respiratory disease (RD) in the elderly (age >or=65 years), and due to asthma in children (age 5-18 years). We examined these associations in the presence of PM(10), PM(2.5) (particulate matter <10 and 2.5 microm in diameter, respectively) and ambient gasses. We utilised data on size distribution to calculate NC(tot) for four modes with median diameters 12, 23, 57 and 212 nm, and NC(100) (number concentration of particles <100 nm in diameter) and examined their associations with health outcomes. We used a time series Poisson generalised additive model adjusted for overdispersion, season, day of the week, public holidays, school holidays, influenza, pollen and meteorology, with up to 5 days' lagged exposure. RESULTS AND CONCLUSIONS: The adverse health effects of particulate matter on CVD and RD hospital admissions in the elderly were mainly mediated by PM(10) and accumulation mode particles with lack of effects for NC(100). For paediatric asthma, accumulation mode particles, NC(100) and nitrogen oxides (mainly from traffic related sources) were relevant, whereas PM(10) appeared to have little effect. Our results suggest that particle volume/mass from long-range transported air pollution is relevant for CVD and RD admissions in the elderly, and possibly particle numbers from traffic sources for paediatric asthma.

Early exposure to smoking and future fecundity among Danish twins.

Several studies have examined the effect of in utero exposure to smoking and fecundity among the offspring but the findings are contradictory. We therefore studied the waiting time to first pregnancy (TTP) and exposure to smoking in utero and childhood among Danish twins born between 1931 and 1952. Information about TTP, exposure to mothers smoking in pregnancy, exposure to smoking in childhood and current smoking among the male twins and smoking in their own pregnancy among female twins was collected by interview. Fecundability odds ratio (FOR) estimating the odds of conception in a cycle among exposed compared to the unexposed were calculated separately for female and male twins. A total of 1653 female and 1598 male twins reported a TTP. Female twins, exposed in utero, had reduced fecundability after control for confounders (FOR = 0.81; 95% CI 0.67-0.99). A nonsignificant increase in fecundity among male twins exposed to smoking in utero was found (FOR = 1.12; 95% CI 0.89-1.40). Among dizygotic twins of opposite sex sharing the same in utero exposures, the future fecundity of the male twin was unaffected by in utero exposure (FOR = 0.97; 95% CI 0.60-1.55) whereas the female twin had reduced fecundity (FOR = 0.65; 95% CI 0.47-0.91). This study supports that smoking is hazardous to the female fetus not only in the short term but also affects her future ability to conceive and makes it even more important to advise pregnant women to stop smoking.

Pubertal development in Danish children: comparison of recent European and US data.

Two recent epidemiological studies (PROS and NHANES III) from the USA noted earlier sexual maturation in girls, leading to increased attention internationally to the age at onset of puberty. We studied the timing of puberty in a large cohort of healthy Danish children in order to evaluate differences between USA and Denmark, as well as to look for possible secular trends in pubertal development. Healthy Caucasian children from public schools in Denmark participated in the study which was carried out in 1991-1993. A total number of 826 boys and 1,100 girls (aged 6.0-19.9 years) were included, and pubertal stages were assessed by clinical examination according to methods of Tanner. In boys testicular volume was determined using an orchidometer. We found that age at breast development 2 (B2) was 10.88 years, and mean menarcheal age was 13.42 years. Girls with body mass index (BMI) above the median had significantly earlier puberty (age at B2 10.42 years) compared with girls with BMI below the median (age at B2 11.24 years, p < 0.0001). Similarly, menarcheal age was significantly lower in girls with BMI above the median compared with girls with BMI below the median (13.12 vs. 13.70 years, p = 0.0012). In Danish boys we found that age at genital stage 2 (G2) was 11.83 years. Both sexes were significantly taller compared with data from 1964, but timing of pubertal maturation seemed unaltered. Finally, puberty occurred much later in Denmark compared with recent data from USA. We could not detect any downwards secular trend in the timing of puberty in Denmark between 1964 and 1991-1993 as seen in the US. Obesity certainly plays a role in the timing of puberty, but the marked differences between Denmark and USA cannot be attributed exclusively to differences in BMI. A possible role of other factors like genetic polymorphisms, nutrition, physical activity or endocrine disrupting chemicals must therefore also be considered. Therefore, we believe it is crucial to monitor the pubertal development closely in Denmark in the coming decades.

A longitudinal study of intrauterine growth and the placental growth hormone (GH)-insulin-like growth factor I axis in maternal circulation: association between placental GH and fetal growth.

The aim of the study was 1) to evaluate the association of maternal serum levels of placental GH and IGF-I with fetal growth, and 2) to establish reference data for placental GH, IGF-I, and IGF-binding protein-3 (IGFBP-3) in normal pregnancies based on longitudinal measurements. A prospective longitudinal study of 89 normal pregnant women was conducted. The women had, on the average, seven blood samples taken and three ultrasound examinations performed. All had normal umbilical artery pulsatility indexes during pregnancy and gave birth to singletons between 37 and 42 wk gestation with birth weights above -2 SD. Placental GH levels were detectable in all samples from as early as 5 wk gestation and increased significantly throughout pregnancy to approximately 37 wk when peak levels of 22 ng/ml (range, 4.64-69.22 ng/ml) were reached. Subsequently, placental GH levels decreased until birth. The change in placental GH during 24.5-37.5 wk gestation was positively associated with fetal growth rate (P = 0.027) and birth weight (P = 0.027). Gestational age at peak placental GH values (P = 0.007) was associated with pregnancy length. A positive association between the change in placental GH and the change in IGF-I levels throughout gestation was found in a multivariate analysis (r(2) = 0.42; P < 0.001). There was no association between placental GH and IGFBP-3 levels. The change in IGF-I throughout gestation (P = 0.039), but not placental GH, was significantly positively associated with placental weight at birth. We found a significant association between placental GH and fetal growth. In addition, we found a highly significant association between the increase in placental GH and the increase in IGF-I. The gestational age at peak placental GH levels was associated with pregnancy length.

Selection bias in determining the age dependence of waiting time to pregnancy.

Many studies have found decreased fecundability, that is, the ability to conceive in a menstrual cycle, with increasing female age. To evaluate the effect of maternal age on waiting time to pregnancy, the authors reviewed hospital charts of all pregnant women attending prophylactic antenatal care at Odense University Hospital, Denmark, during 1972-1987. Only the first pregnancy of each woman and only planned pregnancies were included (n = 14,754). The fecundability odds ratio (FR) was calculated as the odds of a conception in a menstrual cycle among the older women divided by the odds among women aged 15-24 years. The FR for women aged 25-29 years was 1.12 (95% confidence interval (CI): 1.04, 1.20), for women aged 30-34 years it was 1.15 (95% CI: 1.01, 1.30), and for women above 34 years the FR was 2.44 (95% CI: 1.84, 3.22) after adjustment for confounders. The increased fecundability with age is contrary to previous studies and may be explained by selection bias, as sterile women were not included. In addition, some very fertile young women who became pregnant by accident before efficient birth control methods were available and therefore were excluded from time to pregnancy studies may now use oral contraceptives until they plan a pregnancy later in life and are included.

Computer-assisted semen analysis parameters as predictors for fertility of men from the general population. The Danish First Pregnancy Planner Study Team.

The predictive value of sperm motility parameters obtained by computer-assisted semen analysis (CASA) was evaluated for the fertility of men from general population. In a prospective study with couples stopping use of contraception in order to try to conceive, CASA was performed on semen samples from 358 men. A recently developed CASA system, Copenhagen Rigshospitalet Image house sperm Motility Analysis System (CRISMAS) was used for assessment of motility parameters. This system has an editing function which allows correction of tracks made by the computer. Probably due to this function, the concentration assessment made by CRISMAS was very close to that made by the technician (median difference <5%) in all concentration ranges. Correlation between CASA parameters and fertility of normal couples (measured as probability of achieving pregnancy) was examined by the Cox regression model. In univariate models ln(sperm concentration) [beta = 0.331, risk ratio (RR) = 1.392, P = 0.0001], ln(total sperm count) (beta = 0.252, RR = 1.286, P = 0.0007) and percentage motile spermatozoa (beta = 0.014, RR = 1.014, P = 0.0004) were most significant predictors for fertility. In a multivariate analysis ln(sperm concentration) (beta = 0.268, RR = 1.307, P = 0.0016) and percentage motile spermatozoa (beta = 0.010, RR = 1.010, P = 0.011) but even more significantly the combined parameter, ln(concentration of motile spermatozoa) (beta = 0.329, RR = 1.389, P = 0.0001), were the only parameters of predictive value for fertility of men in the general population. In conclusion, these parameters obtained by CASA measurements can be used for prediction of fertility potential in normal men. This appears to be the first study showing the value of CASA in prediction of fertility in the general male population.

Serum levels of growth hormone binding protein in children with normal and precocious puberty: relation to age, gender, body composition and gonadal steroids.

AIM: To study the regulation of GHBP serum levels by gonadal steroids in normal and precocious puberty. STUDY PROTOCOL: We studied GHBP levels in relation to age, sex, pubertal maturation, body composition as well as to circulating IGF-I and gonadal steroid levels in 320 healthy children. Furthermore, we studied the regulation of circulating GHBP in 33 girls with central precocious puberty before and during gonadal suppression with GnRH agonist. METHODS: GHBP was determined by a time-resolved fluoroimmunoassay (GHBP TR-FIA) based on a commercially available immunoassay for GH, the DELFIA GH assay. RESULTS: In healthy children GHBP levels were significantly higher in normal girls compared with boys, and there was no significant increase in GHBP in puberty in both sexes. GHBP levels did not correlate with height (SDS), age, pubertal stage, IGF-I or testosterone/oestradiol levels in boys and girls, respectively. There were significant correlations between BMI and GHBP in boys and girls (R 2 = 0.14 and R 2 = 0.12, both P < 0.0001). Furthermore, GHBP correlated highly significantly with the percentage body fat, determined by BIA in 43 healthy girls (R 2 = 0. 40, P < 0.0001). GHBP levels were significantly higher in girls with central precocious puberty (CPP) (1.31 SDS (1.26), mean (SD)) compared to prepubertal controls (P < 0.0001), and above + 2 SD in 10 out of 33 patients. In girls with CPP, GHBP correlated inversely with oestradiol before treatment (R 2 = 0.26, P < 0.01) and there was a tendency towards a positive correlation with BMI (R 2 = 0.13, P = 0.078). By contrast, there were no signficant correlations between GHBP and IGF-I or height SDS. Gonadal suppression with GnRH agonist treatment caused a transient significant increase of 0.57 SD after 2 months of treatment (P < 0.001), but decreased to baseline levels hereafter. CONCLUSION: We conclude that in children, as in adults, body fat is the primary determinant for the circulating level of GHBP, and that the difference in body fat is probably the main factor for the higher levels of serum GHBP in girls compared with boys, as well as for the negative influence of testosterone levels in boys and of oestrogen levels in girls. The elevation in GHBP levels observed in girls with central precocious puberty is probably due their higher body fat content.

Declining human fertility?

PIP: This article comments on the conclusion reached by Akre et al. in their study on human fertility. Akre et al. concluded that subfertility (measured as a waiting time to pregnancy of 1 year) decreased from 1983 to 1993 in Sweden and that the decline followed a birth cohort pattern. In addition, they speculated that the decrease in subfertility during the 1980s is mainly due to the eradication of gonorrhea. However, the data they presented does not seem to justify their conclusion. The researchers did not study the consequences of truncation of the waiting-time distribution in 1993 and 1983, the association between smoking and infertility, and declining semen quality in order to further support their conclusion.^ieng

Semen quality among Danish and Finnish men attempting to conceive. The Danish First Pregnancy Planner Study Team.

OBJECTIVE: To assess differences in semen quality between similar populations from Denmark and Finland. DESIGN: Comparison of semen quality between 221 Finnish men (of whom 115 had no proven fertility) and 411 Danish men with no proven fertility in two follow-up studies among normal couples trying to conceive. METHODS: In Finland male partners of couples without experienced infertility attempting to conceive were recruited through advertisements in local newspapers from 1984 to 1986. From 1992 to 1995 Danish men who lived with a partner and who had not attempted to achieve a pregnancy previously were recruited through their union when they discontinued birth control. All semen analyses were performed in accordance with the World Health Organization guidelines. RESULTS: Median sperm concentration, total sperm count and the percentage of morphologically normal spermatozoa were significantly higher among the Finnish men without proven fertility (104.0 million/ml, 304.0 million and 58% respectively) compared with the Danish men (53.0 million/ml, 140.8 million, and 41% respectively). Sperm concentration was 105.7% (95% confidence interval (CI) 58.1%-167.6%) and total sperm count was 127.4% (95% CI 71.4%-201.6%) higher among Finnish men without proven fertility than among Danish men after control for confounders. CONCLUSIONS: Some, but hardly all, of the observed difference in semen quality may be explained by differences in recruitment procedures, selection of the men and by methodological differences in semen analysis between the two countries. Also a birth cohort effect may explain some of the differences between countries as the Finnish men were recruited 11 years before the Danish men. Therefore, follow-up studies with identical recruitment and selection of men from the two countries are needed.

The epidemiology of febrile malaria episodes in an area of unstable and seasonal transmission.

This study investigated the epidemiology of uncomplicated falciparum malaria in an area of unstable and seasonal transmission in eastern Sudan. About 90% of malaria morbidity in this region occurs in the months of September to November, and very few malaria cases occur during the intensely arid Sudanese dry season and during years of drought. The malaria situation in the study site, the village of Daraweesh, was analysed during 3 consecutive malaria seasons in 1993-95 during which the 457 inhabitants suffered at total of 436 episodes of falciparum malaria. Using an Andersen-Gill proportional hazard model for recurrent events stratified by family, we have calculated the relative hazard for clinical malaria episodes by age, sex, haemoglobin genotype, blood type and infection in the previous season. The malaria risk was significantly lower in individuals aged 20-88 years than in the 5-19 years age-group. The relative protection due to adulthood varied between seasons (relative risk, RR, 0x34 to 0x67). Serological data were not consistent with the hypothesis that the age difference in incidence was due to differences in exposure. During the 1993 season the malaria incidence in males was lower than in females (RR = 0x75), during the 1994 season the incidences were comparable, whereas males had an increased risk of malaria in 1995 (RR = 1x87). The relative risk in individuals carrying the haemoglobin AS genotype compared to homozygous AA individuals was 0x57.

Fecundability in relation to body mass and menstrual cycle patterns.

Few studies have investigated the association between body mass index and fecundability, that is, the ability to conceive in a menstrual cycle, among fertile women with normal menstrual cycle pattern. We examined the independent and combined effects of duration and regularity of the menstrual cycle, body mass index, and fecundability from records on pregnant women attending antenatal care at Odense University Hospital, Denmark, between 1972 and 1987. We included only the first birth of each woman who had planned pregnancies and no pre-pregnancy disease (N = 10,903). We estimated the fecundability odds ratio (FR) as the odds of conception in a menstrual cycle. After adjusting for confounders, the fecundability for women with a body mass index >25 kg/m2 was lower than for women with a body mass index of 20-25 kg/m2 [FR = 0.77; 95% confidence interval (CI) = 0.70-0.84]. FR was lower for women with long (>35 days) (FR = 0.74; 95% CI = 0.63-0.87) or irregular cycles (FR = 0.78; 95% CI = 0.70-0.87), even when their body mass index was within the normal range (20-25 kg/m2) and/or their cycles were regular.

[Semen quality and fertility in a population-based follow-up study]. / Saedkvalitet og fertilitet i en populationsbaseret followup-undersøgelse.

Little is known about the importance of semen quality in male infertility. We followed 430 first pregnancy planners with no previous reproductive experience recruited among more than 50,000 cohabiting trade-union members. The couples were consecutively enrolled into the study as they discontinued contraception and were followed up for six month menstrual cycles or until a pregnancy was verified. Each man provided a semen sample at enrollment. Women kept daily record of vaginal bleeding and sexual activity. The probability of conception increased with increasing sperm concentration up to 40 x 10(6)/ml, but any higher sperm density was not associated with additional likelihood of pregnancy. The proportion of sperm with normal morphology was strongly related to likelihood of pregnancy, independently of sperm concentration. In conclusion, sperm concentration and morphology are valuable biological markers of male fecundity. Reference values for semen quality based on biological knowledge can be established.

The acid-labile subunit of human ternary insulin-like growth factor binding protein complex in serum: hepatosplanchnic release, diurnal variation, circulating concentrations in healthy subjects, and diagnostic use in patients with growth hormone deficiency.

Circulating insulin-like growth factor-I (IGF-I) is predominantly bound in the trimeric complex comprised of IGF binding protein-3 (IGFBP-3) and acid-labile subunit (ALS). Circulating concentrations of IGF-I, IGFBP-3 and ALS are believed to reflect the GH secretory status, but the clinical use of ALS determination is not known. We therefore, determined the: 1) hepatosplanchnic release of ALS by liver vein catheterization (n=30); 2) 24-h diurnal variation of ALS (n=8); 3) normal age-related ranges of circulating ALS (n=1158); 4) diagnostic value of ALS in 108 patients with childhood-onset GH deficiency (GHD). We found: 1) no significant arteriovenous gradient over the liver ofALS, IGF-I, and IGFBP-3; 2) the diurnal variation of ALS was 12% (mean coefficient of variation percent); 3) ALS levels increased throughout childhood with maximal levels in puberty, with a subsequent decrease with age in adults; and 4) ALS levels were below -2 SD in 57 of 79 GHD patients (sensitivity 72%) and above 2 SD in 22 of 29 patients with normal GH response (specificity 76%), which was similar, compared with the diagnostic utility of IGF-I and IGFBP-3. Finally, our findings indicate that hepatic ALS production is not measurable by this approach or, alternatively, that the liver is not the primary source of circulating ALS, IGF-I, or IGFBP-3 in humans. In conclusion, we have provided extensive normal data for a novel ALS assay and found that circulating ALS levels exhibit minor diurnal variation. We suggest that ALS determination may be used in future classification of adults suspected of GHD.

Year of birth and sperm count in 10 Danish occupational studies.

OBJECTIVES: Several reports indicate a secular decline of human sperm counts. It is still not known if these findings are artifacts related to shortcomings in the data and applied methodologies. Even less is known about possible mechanisms, but it has been proposed that potential changes may be related to disruption of the hormonal regulation of testicular development in prenatal life. The objective of this study was to examine whether sperm count was related to year of birth. METHODS: An analysis was made of the sperm count of 1196 men participating in 10 cross-sectional occupational sperm studies in 3 regions of Denmark from 1986 through 1995. RESULTS: The median sperm concentration was 63 million per milliliter for men born in 1937-1949 and 52 million per milliliter for men born in 1970 or later, and the median total sperm was 206 million and 117 million, respectively. The inverse relationship between sperm concentration and year of birth was statistically significant even after adjustment for duration of sexual abstinence, season of the year, and study population. However, bias because of differential participation related to age and fertility or lack of comparability across the populations cannot be ruled out. CONCLUSIONS: The apparent decline of sperm count with increasing year of birth is compatible with the hypothesis of a common risk factor for male reproductive health operating in prenatal life or early childhood, but the evidence is circumstantial. Age-related selection bias is an alternative and perhaps not a less likely explanation.