Revealing causal effects from correlative data is very challenging and a contemporary problem in human life history research owing to the lack of experimental approach. Problems with causal inference arising from measurement error in independent variables, whether related either to inaccurate measurement technique or validity of measurements, seem not well-known in this field. The aim of this study is to show how structural equation modeling (SEM) with latent variables can be applied to account for measurement error in independent variables when the researcher has recorded several indicators of a hypothesized latent construct.
As a simple example of this approach, measurement error in lifetime allocation of resources to reproduction in Finnish preindustrial women is modelled in the context of the survival cost of reproduction. In humans, lifetime energetic resources allocated in reproduction are almost impossible to quantify with precision and, thus, typically used measures of lifetime reproductive effort (e.g., lifetime reproductive success and parity) are likely to be plagued by measurement error. These results are contrasted with those obtained from a traditional regression approach where the single best proxy of lifetime reproductive effort available in the data is used for inference.
As expected, the inability to account for measurement error in women's lifetime reproductive effort resulted in the underestimation of its underlying effect size on post-reproductive survival.
This article emphasizes the advantages that the SEM framework can provide in handling measurement error via multiple-indicator latent variables in human life history studies.
Sarcopenic muscular degeneration has been consistently identified as an independent risk factor for mortality in aging populations. Recent investigations have realized the quantitative potential of computed tomography (CT) image analysis to describe skeletal muscle volume and composition; however, the optimum approach to assessing these data remains debated. Current literature reports average Hounsfield unit (HU) values and/or segmented soft tissue cross-sectional areas to investigate muscle quality. However, standardized methods for CT analyses and their utility as a comorbidity index remain undefined, and no existing studies compare these methods to the assessment of entire radiodensitometric distributions. The primary aim of this study was to present a comparison of nonlinear trimodal regression analysis (NTRA) parameters of entire radiodensitometric muscle distributions against extant CT metrics and their correlation with lower extremity function (LEF) biometrics (normal/fast gait speed, timed up-and-go, and isometric leg strength) and biochemical and nutritional parameters, such as total solubilized cholesterol (SCHOL) and body mass index (BMI). Data were obtained from 3,162 subjects, aged 66-96 years, from the population-based AGES-Reykjavik Study. 1-D k-means clustering was employed to discretize each biometric and comorbidity dataset into twelve subpopulations, in accordance with Sturges' Formula for Class Selection. Dataset linear regressions were performed against eleven NTRA distribution parameters and standard CT analyses (fat/muscle cross-sectional area and average HU value). Parameters from NTRA and CT standards were analogously assembled by age and sex. Analysis of specific NTRA parameters with standard CT results showed linear correlation coefficients greater than 0.85, but multiple regression analysis of correlative NTRA parameters yielded a correlation coefficient of 0.99 (P
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Cites: J Gerontol A Biol Sci Med Sci. 1999 Apr;54(4):M172-6 PMID 10219007
Cites: J Gerontol A Biol Sci Med Sci. 2006 Oct;61(10):1059-64 PMID 17077199
Department of Public Health and Nursing, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
To ensure optimal calcium accrual in the fetal skeleton, a substantial rise occurs in 1,25-dihydroxyvitamin D (1,25(OH)2D), but is dependent on sufficient 25-hydroxyvitamin (25(OH)D). Large longitudinal studies addressing free 25(OH)D and 1,25(OH)2D during pregnancy are scarce. We aimed to assess levels of and relationship between 25(OH)D, 1,25(OH)2D, vitamin D-binding protein (DBP), parathyroid hormone (PTH), and free 25(OH)D during pregnancy; determinants of vitamin D status; and association between vitamin D indices or PTH and pregnancy outcomes (gestational diabetes mellitus and birthweight). Altogether 855 pregnant Norwegian Caucasian women from Trondheim and Stavanger (latitude 63°N and 58°N) were recruited; 94 were lost to follow-up. The study was originally a randomized controlled trial (2007-2009) with gestational diabetes as primary outcome. Data were collected in second and third trimester. In third trimester, 246 (34%) had vitamin D insufficiency and 52 (7%) deficiency (25(OH)D
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Cites: PLoS One. 2016 Mar 29;11(3):e0152198 PMID 27022948
Cites: N Engl J Med. 2007 Jul 19;357(3):266-81 PMID 17634462
Antibiotics to outpatients in Norway-Assessing effect of latitude and municipality population size using quantile regression in a cross-sectional study.
High antibiotic consumption rates are associated to high prevalence of antimicrobial resistance. Geographical differences in dispensing rates of antibiotics are frequently analysed using statistical methods addressing the central tendency of the data. Yet, examining extreme quantiles may be of equal or greater interest if the problem relates to the extremes of consumption rates, as is the case for antimicrobial resistance. The objective of this study was to investigate how geographic location (latitude) and municipality population size affect antibiotic consumption in Norway. We analysed all outpatient antibiotic prescriptions (n > 14 000 000) in Norway between 2004 and 2010 using quantile regression. Data were stratified by year, and we aggregated individual data to municipality, county, or latitudinal range. We specified the quantile regression models using directed acyclic graphs and selected the model based on Akaike information criteria. Yearly outpatient antibiotic consumption in Norway varied up to 10-fold at municipality level. We found geographical variation to depend on the number of inhabitants in a municipality and on latitude. These variables interacted, so that consumption declined with increasing latitude when municipality population sizes were small, but the effect of latitude diminished as the number of inhabitants increased. Aggregation to different levels of spatial resolution did not significantly affect our results. In Norway, outpatient antibiotic dispensing rates decreases with latitude at a rate contingent on municipality population size. Quantile regression analysis provides a flexible and powerful tool to address problems related to high, or low, dispensing rates.
Mental stress is common in the general population. Mounting evidence suggests that mental stress is associated with multimorbidity, suboptimal care and increased mortality. Delivering healthcare in a biopsychosocial context is key for general practitioners (GPs), but it remains unclear how persons with high levels of perceived stress are managed in primary care. We aimed to describe the association between perceived stress and primary care services by focusing on mental health-related activities and markers of elective/acute care while accounting for mental-physical multimorbidity.
Population-based cohort study.
Primary healthcare in Denmark.
118?410 participants from the Danish National Health Survey 2010 followed for 1?year. Information on perceived stress and lifestyle was obtained from a survey questionnaire. Information on multimorbidity was obtained from health registers.
General daytime consultations, out-of-hours services, mental health-related services and chronic care services in primary care obtained from health registers.
Perceived stress levels were associated with primary care activity in a dose-response relation when adjusted for underlying conditions, lifestyle and socioeconomic factors. In the highest stress quintile, 6.8% attended GP talk therapy (highest vs lowest quintile, adjusted incidence rate ratios (IRR): 4.96, 95%?CI 4.20 to 5.86), 3.3% consulted a psychologist (IRR: 6.49, 95%?CI 4.90 to 8.58), 21.5% redeemed an antidepressant prescription (IRR: 4.62, 95%?CI 4.03 to 5.31), 23.8% attended annual chronic care consultations (IRR: 1.22, 95%?CI 1.16 to 1.29) and 26.1% used out-of-hours services (IRR: 1.47, 95%?CI 1.51 to 1.68). For those with multimorbidity, stress was associated with more out-of-hours services, but not with more chronic care services.
Persons with high stress levels generally had higher use of primary healthcare, 4-6 times higher use of mental health-related services (most often in the form of psychotropic drug prescriptions), but less timely use of chronic care services.
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Cites: BMC Health Serv Res. 2016 Apr 27;16:154 PMID 27122051
Cites: J Health Soc Behav. 1983 Dec;24(4):385-96 PMID 6668417
Tubal ligation results in less advanced stages and lower risk of metastatic spread at diagnosis of endometrial cancer (EC) but the primary preventive effect of the procedure is unclear. In a Swedish nationwide population-based cohort study, we crosslinked registry data for tubal ligation, EC, and death for Swedish women between 1973 and 2010. All women were followed until EC, emigration, hysterectomy for non-cancerous reasons, death, or end of follow-up. Primary outcome was incidence of EC and secondary outcome overall survival. We calculated adjusted incidence rates (IR) per 100,000 person-years and hazard ratios (HR) using Cox regression models. A total of 35,711 cases of EC were identified among 5,385,186 women. The IR of EC among exposed was 17.7 (95% CI 15.7-19.9) versus 29.0 (95% CI 28.7-29.3) among unexposed (per 100,000 women years). Exposed individuals had significantly reduced risk of EC (HR 0.73, 95% CI 0.65-0.83). The mortality rate among women with EC was 72% lower in exposed compared to unexposed (IR 1,441; 95% CI 1,089-1,907 and IR 5,136; 95% CI 5,065-5,209, respectively) which following adjustment corresponded to a HR of 0.71 (95% CI 0.49-1.03). Tubal ligation was associated with lower risk of EC as well as mortality rates in women with EC. Elective tubal ligation may be adopted in future cancer preventive strategies but must be balanced against the irreversibility of the procedure, which preclude further unassisted reproduction.
The ADRA2B gene 301-303 I/D polymorphism is associated with various cardiovascular phenotypes. However, an association of genotypes with the timing structure of cardiac cycle remains unclear. The central hemodynamic parameters were assessed by pulse wave analysis in 63 residents of the Kola Peninsula (68 N) aged 27-65 yr. The genotypes were determined by PCR. The paired comparisons revealed that II genotype carriers had higher values of augmentation index ( P = 0.014), ejection duration ( P = 0.045), and lower SEVR ( P = 0.035) than DD homozygotes. Multiple regression analysis adjusted for age, body mass index, heart rate, and blood pressure confirmed these results. Further sex stratified analysis showed that the associations existed only in men ( n = 33) whereas in women ( n = 30) the differences were suggestive ( P
To explore the associations between self-rated attachment style, psychological distress and substance use among substance use disorder (SUD) outpatients in psychological treatment.
In this practice-based study, 108 outpatients were asked to fill in the Experiences in Close Relationships - Short form, the Clinical Outcomes in Routine Evaluation - Outcome Measure (CORE-OM), the Alcohol Use Disorders Identification Test (AUDIT), and the Drug Use Disorders Identification Test (DUDIT) at treatment start and end. Patients were given psychological treatments with a directive, reflective or supportive orientation.
An insecure attachment style was more common among the SUD outpatients, compared to non-clinical groups. Patients with a fearful attachment style scored higher on psychological distress than patients with a secure attachment style. The associations between the attachment dimensions and psychological distress were stronger than those between attachment and SUD. Significantly more patients had a secure attachment style at treatment end.
This study shows significant relations between patients' attachment style and their initial psychological distress. The causal relationship between attachment style and psychological distress is, however, not clear and can likely go in both directions. The psychological treatment of patients with SUD contributed significantly to changes from insecure to secure attachment style.
We found among patients with SUD a strong relation between patients' attachment style and their psychological distress. Knowledge of the patient's attachment style may help the therapist to tailor the treatment to the patient's needs. A change from insecure to secure attachment style can be an important goal for a SUD treatment, as it may prevent the patient from using defence strategies involving substance use for regulating emotions and interpersonal relationships.
Pharmacoepidemiological studies have long raised concerns on widespread use of benzodiazepines and benzodiazepine-related drugs (BZDs), in particular long-term use, among adults and the elderly. In contrast, evidence pertaining to the rates of BZD use at younger ages is still scarce, and the factors that influence BZD utilisation and shape the different prescribing patterns in youths remain largely unexplored. We examined the prevalence rates, relative changes in rates over time, and prescribing patterns for BZD dispensation in young people aged 0-24 years in Sweden during the period January 1, 2006-December 31, 2013, and explored demographic, clinical, pharmacological, and prescriber-related attributes of BZD prescribing in this group.
Through the linkage of 3 nationwide Swedish health and administrative registers, we collected data on 17,500 children (0-11 years), 15,039 adolescents (12-17 years), and 85,200 young adults (18-24 years) with at least 1 dispensed prescription for a BZD during 2006-2013, out of 3,726,818 Swedish inhabitants aged 0-24 years. Age-specific annual prevalence rates of BZD dispensations were adjusted for population growth, and relative changes in rates were calculated between 2006 and 2013. We analysed how BZD dispensation varied by sex, psychiatric morbidity and epilepsy, concurrent dispensation of psychotropic medication, type of dispensed BZD, and type of healthcare provider prescribing the BZD. Prescribing patterns were established in relation to duration (3 months, >3 to =6 months, or >6 months), dosage ( 6 months). The study limitations included lack of information on actual consumption of the dispensed BZDs and unavailability of data on the indications for BZD prescriptions.
The overall increase in prevalence rates of BZD dispensations during the study period and the unexpectedly high proportion of individuals who were prescribed a BZD on a long-term basis at a young age indicate a lack of congruence with international and national guidelines. These findings highlight the need for close monitoring of prescribing practices, particularly in non-psychiatric settings, in order to build an evidence base for safe and efficient BZD treatment in young persons.
Studies confirm that calcium inhibits iron absorption. Danish tap water comes from groundwater, which contains varying amounts of calcium depending on the subsoil. We investigated the association of calcium in drinking water with iron levels in Danish blood donors.
We used data on Danish blood donors including dietary and lifestyle habits, blood donation history, and physiologic characteristics including measures of ferritin levels along with information on area of residence from The Danish Blood Donor Study. Data on calcium levels in groundwater ("water hardness") were obtained through the Geological Survey of Denmark and Greenland. We performed multiple linear and logistic regression analyses to evaluate the effect of water hardness on ferritin levels and risk of having iron deficiency (defined as ferritin levels
