Associations between variability of risk factors and health outcomes in longitudinal studies

Many statistical methods have been developed that treat within‐subject correlation that accompanies the clustering of subjects in longitudinal data settings as a nuisance parameter, with the focus of analytic interest being on mean outcome or profiles over time. However, there is evidence that in certain settings, underlying variability in subject measures may also be important in predicting future health outcomes of interest. Here, we develop a method for combining information from mean profiles and residual variance to assess associations with categorical outcomes in a joint modeling framework. We consider an application to relating word recall measures obtained over time to dementia onset from the Health and Retirement Survey. Copyright © 2012 John Wiley & Sons, Ltd.     

Associations between positive changes in perceived work characteristics and changes in fatigue

Little is known about the natural course of fatigue among employees. An adequate understanding of its development and risk factors is important to prevent chronic health complaints and absenteeism. This longitudinal study investigated associations between positive changes in perceived work characteristics (ie, a decrease in job demands, an increase in decision latitude, and an increase in social support) and changes in fatigue by performing hierarchical regression analyses. The work characteristics of the demand-control-support model were selected as predictors. The outcome measures emotional exhaustion and psychologic distress were investigated as secondary outcomes. The results showed that, compared with a stable work situation, positive changes in perceived social support, decision latitude, and psychologic job demands went together with a decrease in fatigue. Similar results were found for the secondary outcomes emotional exhaustion and psychologic distress.     

Plasma testosterone,serum FSH,and serum LH levels in transvestism

Plasma testosterone, serum FSH, and serum LH levels of 26 members of a club established for heterosexual transvestites were assayed. Mean plasma testosterone, serum FSH, and serum LH levels of the transvestite subjects were not significantly different from the normal range. The implications of these findings are discussed.This work was supported by the National Health and Medical Research Council of Australia.     

剖析雌激素替代治疗前后血清ApoA-I、B及其他血脂的变化

目前我国对绝经后妇女用ERT防治冠心病的工作尚未普及.为此,我们检测了部分更年期妇女及雌激素替代治疗后的血清载脂蛋白、血脂、雌激素、FSH水平,以探讨更年期妇女血清载脂蛋白及血脂水平与雌激素变化的关系,进一步说明雌激素替代治疗的临床意义.     

Associations between anxious-depressed symptoms and cardiovascular risk factors in a longitudinal childhood study

Objective

To examine the influence of anxious/depressed scores on cardiovascular risk factors throughout childhood.

Methods

Data from the Western Australian Pregnancy Cohort (Raine) Study, a study of 2900 pregnancies recruited between 1989 and 1991, were used. Anxious-depressed scores (derived from the Childhood Behavior Checklist), body mass index (BMI) and blood pressure were measured at 5 (n = 1681), 8 (n = 1697), 10 (n = 1575) and 14 (n = 1386) years. At age 14 depressive symptom scores (Beck Depression Inventory for Youth), anxious-depressed scores (Youth Self-Report (YSR) and Teacher Report Form (TRF)) and fasting lipid, glucose and insulin were also available. Cross sectional and longitudinal analyses were conducted.

Results

At age 14, girls with higher anxious-depressed scores had higher BMI (p ≤ 0.005) and homeostasis model assessment-estimated insulin resistance (p ≤ 0.0001). This equated to a difference of 0.6 kg/m² and 0.3 units in predicted BMI and HOMA-IR respectively (top 5% vs. score of zero). Boys with higher anxious-depressed scores had lower systolic blood pressure trajectories (p = 0.024).

Conclusion

Depressive scores appear to have differing influences on BMI, homeostasis model assessment-estimated insulin resistance and systolic blood pressure in boys and girls. Paradoxically boys with higher anxious-depressed scores had lower blood pressure throughout childhood.     

Associations between relationship stability,relationship quality,and weight loss outcomes among bariatric surgery patients

After weight loss surgery (WLS), psychosocial functioning, including the quality of social relationships, generally improves, but for a minority, relationships worsen. We examined how changes in relationship stability and quality from pre- to post-WLS relate to long-term weight loss outcomes. Postoperative patients (N = 361) completed surveys which queried relationship changes and weight loss. The sample was 95.9% Caucasian, 80.1% female, averaged 7.7 years post-WLS, with a mean age at surgery of 47.7 years (range 21–72); 87.3% had a Roux-en-Y gastric bypass. Four relationship status groups were created: Not in a relationship at surgery or follow-up (No-Rel, n = 66; 18.2%); Post-WLS relationship only (New-Rel, n = 23; 6%); Pre-WLS relationship only (Lost-Rel, n = 17; 5%); and Pre–Post Relationship (Maintainer, n = 255; 70.6%). Current BMI was 34.5 for No-Rel; 40.5 for New-Rel; 37.4 for Lost-Rel; 33.3 for Maintainers (p < .05 for Maintainers and No-Rel vs. New-Rel). These same group differences were significant for weight loss, which was not associated with gender, time since surgery, or age at time of surgery, but was associated with pre-WLS BMI (lower pre-WLS BMI was associated with greater %EWL). Analyses were repeated with pre-WLS BMI as a covariate; group differences remained significant [F (3, 355) = 3.09, p = .03], as did pre-WLS BMI, [F (1, 355) = 9.12, p = .003]. Among Maintainers, relationship quality was associated with weight loss outcomes: those with improved relationships post-WLS had significantly greater %EWL [F (2, 234) = 15.82, p < 0.000; p < .05 for Improved > (Stayed Same = Got Worse)]. Findings support the importance of assessing relationship stability and quality in pre-WLS candidates, as healthy and stable relationships may support improved long-term outcomes. Interventions to improve relationships pre-and post-WLS may increase both quality of life and weight loss outcomes.     

Associations between obesity and serum lipid-soluble micronutrients among premenopausal women

Elucidating potential pathways that micronutrients may reduce/promote chronic disease may contribute to our understanding of the underlying etiology of disease and their utility as markers of risk. In the current study, we examined associations of serum lipid-soluble micronutrients with body mass index (BMI). We hypothesized that obesity may differentially influence serum micronutrient levels, thereby affecting risk for chronic disease incidence and mortality. Baseline serum samples from 180 premenopausal women from a nutritional trial were analyzed for leptin, C-reactive protein, 25-hydroxyvitamin D, carotenoids, and tocopherols. Participants were stratified into normal-weight (18.5-24.9), overweight (25-29.9), and obese (≥30) subgroups by BMI (in kilograms per square meter). Differences in serum biomarkers among BMI subgroups were adjusted for Asian ethnicity and smoking status. As expected, obese individuals had significantly higher serum levels of leptin and C-reactive protein (Ps < .05) compared with normal-weight women. γ-Tocopherol levels were significantly higher in obese individuals (P < .05), whereas α-tocopherol levels did not differ among BMI subgroups. Serum levels of 25-hydroxyvitamin D and carotenoids (except lycopene) were significantly lower in obese than in normal-weight women (Ps < .05). The associations between BMI and carotenoids were independent of dietary intake. The obesity-associated reduction for total provitamin A carotenoids (45%) was approximately 3-fold greater than that observed for non–provitamin A carotenoids (16%). Our results indicate potential influences of obesity on serum levels of lipid-soluble micronutrients and suggest that metabolism of provitamin A carotenoids may contribute to the differences observed.     

Associations between short-term changes in nitrogen dioxide and mortality in Canadian cities

The association between daily variations in ambient concentrations of nitrogen dioxide (NO2) and mortality was examined in 12 of Canada's largest cities, using a 19-yr time-series analysis (from 1981-1999). The authors employed parametric statistical methods that are not subject to the recently discovered convergence and error estimation problems of generalized additive models. An increase in the 3-d moving average of NO2 concentrations equivalent to the population-weighted study mean of 22.4 ppb was associated with a 2.25% (t = 4.45) increase in the daily nonaccidental mortality rate and was insensitive to adjustment for ozone, sulfur dioxide, carbon monoxide, coefficient of haze, size-fractionated particulate mass, and the sulfate ion measured on an every-6th-day sampling schedule. The 3-d moving average of NO2 was sensitive to adjustment for fine particulate matter measured daily during the 1998-2000 time period.     

Associations between serum calcium,phosphorus and mortality among patients with coronary heart disease

Purpose

Serum calcium and phosphorus abnormalities are associated with cardiovascular disorders in general population, but evidence among patients with established coronary heart disease (CHD) is limited and controversial. This study aimed to investigate the associations of baseline serum calcium and phosphorus levels with long-term mortality risk among patients with CHD.

Methods

We conducted a prospective cohort study among 3187 patients with CHD from October 2008 and December 2011 in China. Cox proportional hazards model was used to assess the associations of serum calcium and phosphorus at baseline with the risk of death.

Results

During follow-up (mean, 4.9 years), 295 patients died, 193 of which resulted from cardiovascular causes. Multivariable-adjusted hazard ratios (HR) for each 1 mmol/L increase in serum calcium at baseline were 0.27 (95% confidence interval (CI) 0.14–0.51) for all-cause mortality and 0.26 (95% CI 0.12–0.54) for cardiovascular mortality. Patients in the highest compared to the lowest quartile of serum calcium were at lower risk of all-cause mortality (HR, 95% CI 0.57, 0.40–0.82) and cardiovascular mortality (0.50, 0.32–0.79) (both P _trend < 0.001). This inverse association between serum calcium and the risk of mortality did not change when participants were stratified by sex, age groups, level of overweight, types of CHD, and history of diabetes. We also observed a graded positive association between baseline serum phosphorus and the risks of mortality.

Conclusions

The present study is the first to report that lower serum calcium at baseline is associated with an increased risk of all-cause and cardiovascular mortality in a Chinese coronary heart disease cohort. Further studies are required to investigate the causal relationship and actual mechanisms.

     

A longitudinal analysis of the relationship between changes in socio-economic status and changes in health

In this paper we contribute to discussion on the relationship between different aspects of socio-economic status (SES) and health. Separating different aspects of SES facilitates the specification of a structural relationship between SES indicators and morbidity. Longitudinal data and the utilization of growth curve modelling enable an empirical analysis of the direct relationship between changes over time in SES indicators and changes in morbidity. Our empirical analysis is based on panel data (N = 2976) derived from the annual Swedish Survey of Living Conditions. The panel, which consists of respondents that at the first panel wave were between 31 and 47 years old, is followed for 16 years, starting in 1979. Data are gathered at three points of time. A growth curve model is set up using structural equation modelling. The structural relationship and changes over time are simultaneously estimated. It is shown that in relation to health occupational position is crucial, canalising the effects of class of origin and education. More prestigious jobs are related to initially good health and to a less rapid deterioration in health. At the same time initial health affects occupational mobility, confirming a health selection into less prestigious jobs. It is also shown that change of occupation and income are related to change in health. The analysis confirms a strong relationship between SES and morbidity and shows that initial SES affects later changes in morbidity, i.e., a causal relationship exists between SES and morbidity. But, the analysis also demonstrates the existence of selection effects, meaning that initial morbidity causes less favourable changes in SES. It is finally revealed that changes in occupational prestige and income changes co-vary with changes in morbidity. Hence, the analysis provides basic information necessary to make any assumption about causality and selection in relation to SES and health.     

Nonlinear association between serum testosterone levels and coronary artery disease in Iranian men

Previous studies have shown controversial results about the role of androgens in coronary artery disease (CAD). We performed this study to examine and compare the relationship between androgenic hormones and CAD using conventional linear statistical techniques as well as novel non-linear approaches. The study was conducted on 502 consecutive men who were referred for selective coronary angiography at Tehran Heart Center due to different indications. We studied the relationship between androgenic hormones and CAD by using the generalized linear models, generalized additive models, and neural networks. Free testosterone (fT), total testosterone (tT) and dehydroepiandrosterone sulfate levels in patients with significant CAD versus normal individuals were 6.69 ± 3.20 pg/ml, 16.60 ± 6.66 nm/l, and 113.38 ± 72.9 μg/dl versus 7.12 ± 3.58 pg/ml, 15.82 ± 7.26 nm/l, and 109.03 ± 68.19 μg/dl, respectively (P > 0.05). The Generalized linear models was unable to show any significant relationship between androgenic hormones and CAD, while generalized additive model and neural networks supported the significant effect of androgenic hormones on CAD. This finding suggests a nonlinear association of tT levels with CAD: lower levels have a preventive effect on CAD, whereas higher values increase the risk of CAD. Emphasizing the non-linearity of the variables may provide new insight into the possible explanation of the effect of androgenic hormones on CAD.     

Influence of DDT,DDVP and malathion on FSH,LH and testosterone serum levels and testosterone concentration in testis

Summary Groups of adult male rats were treated with DDT, DDVP or malathion orally for two or three weeks. Body weight and testis weight did not change. FSH and LH levels in serum also remained unchanged, whereas that of testosterone was decreased by DDT. This substance also diminished the concentration of testosterone in the testis. Therefore, the previously observed damage to spermatogenesis by DDT are assumed to be caused by a lack of androgens. Those following treatment with DDVP or malathion seem to be due to a direct cytotoxic effect.     

Associations between changes in physical fitness and psychological difficulties status among Norwegian adolescents

ObjectivesTo investigate the associations for one-year changes in cardiorespiratory fitness, muscular strength and body mass index, with psychological difficulties status in adolescents.MethodsNorwegian 14-15-year-olds (n = 925) participated in data collection at two time points separated by one year. Psychological difficulties were assessed via the Strengths and Difficulties questionnaire and data from follow-up serve as the dependent variable. Cardiorespiratory fitness (the Andersen-test), muscular strength (Eurofit) and body mass index were measured. Change scores were calculated from the physical fitness variables and serve as independent variables in linear mixed effects models.ResultsThere was no association between change in body mass index and psychological difficulties. Sex and socioeconomic status moderated the association between cardiorespiratory fitness and psychological difficulties. Immigrant status moderated the association between muscular strength and psychological difficulties. Subgroup results indicated inverse associations between change in cardiorespiratory fitness and psychological difficulties among boys (b = −0.009; 95% CI = −0.015 to −0.003; p = .006); change in muscular strength and psychological difficulties among immigrants (b = −1.97; 95% CI = −4.03 to 0.09; p = .061). Subgroup results also indicated an association between change in cardiorespiratory fitness and psychological difficulties among girls in the highest socioeconomic group (b = 0.014; 95% CI = 0.003 to 0.025; p = .014).ConclusionsThe associations for different fitness components were dependent on different moderators. Possibly, this indicates that associations in different subgroups are mediated by different mechanisms. Moderated associations should be addressed in future investigations.     

A longitudinal examination of factors related to changes in serum polychlorinated biphenyl levels

Consumption of sport-caught fish from the Great Lakes is a recognized source of human exposure to polychlorinated biphenyls (PCBs). Understanding temporal changes in PCB body burden is crucial for evaluating exposure levels and augmenting validity of studies investigating their relationship to adverse health effects. Using data collected from 1980 to 1995, we evaluated longitudinal changes in serum PCB levels among 179 fisheaters and non-fisheaters of the Michigan Fisheater Cohort. Participants identified as fisheaters in 1980 ate 26 lb or more of sport-caught fish per year, whereas non-fisheaters ate less than 6 lb per year. We found a monotonic decline in serum PCB levels among all participants from a mean value of 24 ppb in 1980 to 12 ppb in 1994. This was paralleled by an 83% decrease in mean fish consumption among all participants over the same period. We combined demographic, lifestyle, and fish consumption information with PCB data and evaluated the data using regression models to identify predictors of PCB body burden over a 16-year period. Results of the mixed-effects linear regression model suggest that consumption of Lake Michigan fish before 1980, amount of sport-caught fish eaten in the past year, age, and year of data collection were significant determinants of current PCB body burden over the 16-year study period. PCB levels were particularly elevated for males who were classified as fisheaters in 1980, which may reflect higher levels of sport-caught fish consumption compared with female fisheaters.     

Interactive effects between polymorphisms in the beta-adrenergic receptors and longitudinal changes in obesity

We assessed interactions between polymorphisms in the beta-adrenergic receptor genes and longitudinal changes in obesity from childhood to adulthood using longitudinal data collected over a 24-year period from 1973 to 1996. Sex- and age-stratified analyses using random coefficients models were used to examine gene-gene interaction effects on obesity measures in 1179 African-American and white men and women (71% white, 57% women). Suggestive evidence for an interaction (p = 0.022) between the beta1- and beta2-adrenergic receptors was observed in men for longitudinal change in BMI. Men with Gly/Gly genotypes for both the beta1 and beta2 receptors showed significant increases (approximately 0.6%/yr) in BMI from childhood to adulthood. Women showed suggestive evidence for an interaction (p = 0.035) between the beta1- and beta3-adrenergic receptors for change over time in BMI. Women with Gly/Gly genotypes at the beta1-receptor and carrying at least one beta3-Arg allele showed notable increases in BMI. The regulation of lipolysis and development of obesity differ markedly between men and women and may be influenced by genetic polymorphisms, which contribute to the efficiency of the beta-adrenergic receptors, and hormonal effects on adrenergic receptor activity.