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PubMed2004

Explaining fruit and vegetable consumption: the theory of planned behaviour and misconception of personal intake levels.

The influence of individuals' misconceptions in assessing fruit and vegetable consumption on the ability of the theory of planned behaviour to explain variance in the consumption of these foods was studied. Dutch women (mean age 41, n=159) completed a questionnaire assessing the theory's constructs with regard to the daily consumption of at least two pieces of fruit and 200 gram of vegetables. Consumption was assessed using a self-rated measure and more objectively with a food-frequency questionnaire. Both measures were combined to classify participants according to the accuracy of their self-assessed intake levels ('realists' vs. 'overestimators'). The model explained variation in objective fruit and vegetable intake much better among realists (R2 = 45% for fruits and 39% for vegetables) than among overestimators (R2 = 18% and 5%, respectively). Perceived behavioural control was the strongest predictor of intentions and behaviour. When plasma vitamin C and carotenoid concentrations were used as objective indicators for fruit and vegetable intake, the explanatory value of the model was lower, but again more variance was explained among realists than among overestimators. We conclude that awareness of personal behaviour should be taken into account when applying the theory of planned behaviour to explain dietary behaviours as well as to design health education interventions.

Adult↗
PubMed2005

To what extent do variabilities in hormones, metabolites and energy intake explain variability in milk yield?

The objective of the present paper is to describe the extent to which variability in milk yield can be explained by variability in plasma hormones, metabolites and DE intake. Results from a study including 317 cows and 634 lactations were used. Detailed registration of performance was carried out on these cows and 10,809 plasma samples analyzed for selected hormones and metabolites. Univariate analysis was carried out on energy-corrected milk yield and concentrations of selected plasma hormones (insulin, growth hormone (GH) and triiodothyronine (T3)), metabolites (non-esterified fatty acids (NEFA)), glucose, beta-hydroxybutyrate (BOHB) and urea nitrogen (BUN), and digestible energy intake (DE intake) to estimate between-cow variation through lactations. Partial least square (PLS) models were subsequently run to estimate the extent to which between-cow differences in energy-corrected milk yield could be explained by between-cow differences in hormone concentrations, metabolite concentration or DE intake. The between-cow variability in energy-corrected milk yield and the hormones and metabolites were generally found to be considerable and total variance changed through lactation, particularly for GH, T3, NEFA and BOHB. In this study, the total variance was highest in third lactation cows. When analyzed separately using partial least square models, hormones, metabolites and DE intake accounted for 24, 25 and 26% of the variability in ECM, respectively. Insulin and glucose were the single most important predictors among the selected hormones and metabolites. When including both the hormones and metabolites, the model explained 36% of the between-cow variability in ECM and this figure was increased to 53% if DE intake was also included. The lack of additivity in the variability explained shows that hormones, metabolites and DE intake were correlated illustrating the integration and orchestration of metabolism and intake. Perspectives of the analysis for use in prevention of diseases and reproduction are briefly discussed.

3-Hydroxybutyric Acid↗
PubMed2006

The role of conduct disorder in explaining the comorbidity between alcohol and illicit drug dependence in adolescence.

BACKGROUND: Conduct disorder (CD), alcohol dependence (AD), and illicit drug dependence (IDD) frequently co-occur. This paper describes the result of an investigation of the extent to which comorbid alcohol and illicit drug dependence in adolescents are explained by etiological factors in common with conduct disorder. METHODS: Participants were 645 MZ twin pairs, 702 DZ twin pairs, 429 biological sibling pairs, and 96 adoptive sibling pairs, aged 12-18 years, from a community based sample. Conduct disorder was measured using the Diagnostic Interview Schedule for Children-IV. Alcohol and illicit drug dependence were assessed using the Composite International Diagnostic Interview-Substance Abuse Module (CIDI-SAM). For each outcome, subjects were categorized into those with no symptoms, those with one or more symptoms but no diagnosis, and those with a diagnosis. RESULTS: The heritability estimates for CD, AD, and IDD were 58, 66, and 36%, respectively. The genetic correlation between AD and IDD was partially explained by the genetic risk they both share with conduct disorder. CONCLUSIONS: We conclude that conduct disorder in adolescents explains, in part, the co-occurrence of alcohol and illicit drug dependence. Specifically, the genetic contribution to their covariation is explained partially by the genetic contribution in common with conduct disorder.

Adolescent↗
PubMed2006

Explaining sex differences in chronic musculoskeletal pain in a general population.

Many studies report a female predominance in the prevalence of chronic musculoskeletal pain (CMP) but the mechanisms explaining these sex differences are poorly understood. Data from a random postal questionnaire survey in the Dutch general population were used to examine whether sex differences in the prevalences of CMP are due to sex differences in the distribution of known potential risk factors for CMP (exposure model) and/or to the different importance of risk factors for CMP (i.e. show different strength of association) in men and women (vulnerability model). In the present analyses, 909 men and 1178 women aged 25-65 were included. CMP was defined as pain lasting longer than 3 months and was assessed for 10 anatomical locations (neck, shoulder, higher back, elbow, wrist/hand, lower back, hip, knee, ankle, foot). Sex differences in CMP could not be explained by a different distribution of age, educational level, smoking status, overweight, physical activity, and pain catastrophizing. Having no paid job was associated with CMP, explaining part of the sex differences, but its role seems complex. Risk factors with a sex-specific association were: overweight (all pain locations) and older age (lower extremities)--both having only an effect among women--and pain catastrophizing (upper extremities), which was stronger associated with CMP among men than among women. In conclusion, sex differences in prevalence of CMP may partly be explained by sex differences in vulnerability to risk factors for CMP. Future research towards sex-specific identification of risk factors for CMP is warranted. Eventually this may lead to sex-specific prevention and management of CMP.

Adult↗
PubMed2002

Deterministic rather than stochastic factors explain most of the variation in the expression of skin telangiectasia after radiotherapy.

BACKGROUND: The large patient-to-patient variability in the grade of normal tissue injury after a standard course of radiotherapy is well established clinically. A better understanding of this individual variation may provide valuable insights into the pathogenesis of radiation damage and the prospects of predicting the outcome. PURPOSE: To estimate the relative importance of the stochastic vs. patient-related components of variability in the expression of radiation-induced normal tissue damage. METHODS AND MATERIALS: The study data were selected from the dose fractionation studies of Turesson in Gothenburg. Patients treated with bilateral internal mammary fields, who completed at least 10 years of follow-up, were included. The material included 22 different fractionation schedules (11 on each side). Telangiectasia was graded on an arbitrary 6-point scale using clinical photographs of the irradiated fields. For each field, in each patient, a curve showing the grade of telangiectasia as a function of time was constructed. A measure of radioresponsiveness was obtained from the difference between the area under the curve (AUC) for a specific field in an individual patient minus the mean AUC of fields receiving the same dose fractionation schedule. As a confirmatory procedure, the same analysis was repeated with a weighted area under the curve (WAUC) approach, in which the time spent at or above each of the 5 nonzero grades was calculated for each field in each patient. These times were used as explanatory variables in a linear regression analysis of biological equivalent dose to establish statistically the weight of each grade providing the optimal relationship between dose and effect. Using these regression coefficients, the weighted area under the grade-time curve (WAUC) was estimated. RESULTS: The AUC was significantly correlated with the isoeffective dose in 2-Gy fractions (ID2). An analysis of variance components, using the maximum likelihood method, showed that 90% (with 95% confidence limits 65% and 100%) of the variance in radioresponsiveness in the right-sided field was explained by the radioresponsiveness on the left-sided field. Through the linear regression analysis between the AUC and the ID2, it was estimated that patients with a reaction that is 1 SD from the population mean would require a dose modification of approximately 23 Gy (from the group mean of 56 Gy) to give them a level of reaction similar to the group average. Similarly, the WAUC was significantly correlated with the ID2, and 81% (with 95% confidence limits 49% and 100%) of the variance in radioresponsiveness in the right-sided field was explained by the radioresponsiveness on the left-sided field. Patients with a reaction that is 1 SD from the population mean would require a dose modification of approximately 21 Gy (from the group mean of 56 Gy) to give them a level of reaction similar to the group average. CONCLUSION: For a given fractionation schedule, patient-related factors explain 81-90% of the patient-to-patient variation in telangiectasia level seen after radiotherapy. The remaining 10-19% are explained by stochastic effects. This observation encourages further research into genetic or phenotypic assays of normal tissue radioresponsiveness.

Analysis of Variance↗
PubMed2002

Falls explain between-center differences in the incidence of limb fracture across Europe.

There is important geographic variation in the occurrence of the major osteoporotic fractures across Europe. The aim of this study was to determine whether between-center variation in limb fracture rates across Europe could be explained by variation in the incidence of falls. Men and women, aged 50-79 years, were recruited from population-based registers in 30 European centers. Subjects were followed by postal questionnaire to ascertain the occurrence of incident fractures, and were also asked about the occurrence and number of recent falls. Self-reported fractures were confirmed, where possible, by review of the radiographs, medical record, or subject interview. The age- and gender-adjusted incidence of falls was calculated by center using Poisson regression. Poisson regression was also used to assess the extent to which between-center differences in the incidence of limb fractures could be explained by differences in the age- and gender-adjusted incidence of falls at those centers. In all, 6302 men (mean age 63.9 years) and 6761 women (mean age 63.1 years) completed at least one questionnaire concerning fractures and falls. During a median follow-up time of 3 years, 3647 falls were reported by men and 4783 by women. After adjusting for age and gender, there was evidence of significant between-center differences in the occurrence of falls. There was also between-center variation in the occurrence of upper limb, lower limb, and distal forearm fractures. Variation in the age- and gender-adjusted center-specific fall rates explained 24%, 14%, and 6% of the between-center variation in incidence of distal forearm and upper and lower limb fractures, respectively. Given the constraints inherent in such an analysis, in men and women aged 50-79 years, variation in fall rates could explain a significant proportion of the between-center variation in the incidence of limb fracture across Europe.

Accidental Falls↗
PubMedDate not supplied

A temporal model for early vision that explains detection thresholds for light pulses on flickering backgrounds.

A model is presented for the early (retinal) stages of temporal processing of light inputs in the visual system. The model consists of a sequence of three adaptation processes, with two instantaneous nonlinearities in between. The three adaptation processes are, in order of processing of the light input: a divisive light adaptation, a subtractive light adaptation, and a contrast gain control. Divisive light adaptation is modeled by two gain controls. The first of these is a fast feedback loop with square-root behavior, the second a slow feedback loop with logarithm-like behavior. This can explain several aspects of the temporal behavior of photoreceptor outputs. Subtractive light adaptation is modeled by a high-pass filter equivalent to a fractional differentiation, and it can explain the attenuation of low frequencies observed in ganglion cell responses. Contrast gain control in the model is fast (Victor, 1987), and can explain the decreased detectability of test signals that are superimposed on dynamic backgrounds. We determine psychophysical detection thresholds for brief test pulses that are presented on flickering backgrounds, for a wide range of temporal modulation frequencies of these backgrounds. The model can explain the psychophysical data for the full range of modulation frequencies tested, as well as detection thresholds obtained for test pulses on backgrounds with increment and decrement steps in intensity.

Adaptation, Ocular↗
PubMed2002

How people explain actions performed by groups and individuals.

The authors explore whether people explain intentional actions performed by groups differently from actions performed by individuals, A theoretical framework is offered that distinguishes between 2 modes of explanation: the agent's reasons (beliefs or desires in light of which the agent decided to act) and causal histories of reasons (CHRs; factors that preceded and brought about the agent's reasons). The authors develop the hypothesis that people use more CHR explanations when explaining group actions than when explaining individual actions. Study 1 demonstrates this asymmetry. Studies 2 and 3 explore 2 necessary conditions for the asymmetry: that the group be perceived as an aggregate of individual actors rather thin as a jointly acting group and that explainers have general information available about the group. Discussion focuses on people's perception of groups as entities and agents.

Humans↗
PubMed2003

Which factors explain the lower prevalence of atopy amongst farmers' children?

BACKGROUND: The inverse association between farming and atopy in children has been attributed to microbial exposure, especially through livestock. Very little is known about other potential explanatory factors. OBJECTIVE: To explore potential differences in lifestyle and environmental factors between farmer and non-farmer families, and whether these factors could explain the association between farming and childhood atopy. METHODS: A cross-sectional study, including 366 farmers' and 344 non-farmers' children in eastern Finland. Information regarding exposure and background characteristics was gathered by a written questionnaire. Atopy was defined as having one or more positive skin prick test reactions (> 3 mm) against the six common aeroallergens. RESULTS: Regardless of the current farming type, atopy was less frequent among the farmers' children than the non-farmers' children (aOR 0.56, 95% CI 0.40-0.78). Remarkable differences were seen in many lifestyle factors (including diet) between the farmer and non-farmer families, but only a few of the explored factors were associated with atopy. The frequency of current livestock contacts seemed to have an inverse, dose-dependent association with atopy (aOR 0.46, 95% CI 0.22-0.97 for daily vs. no contact). Having lived on a dairy farm in infancy (aOR 0.51, 95% CI 0.28-0.93), or having had cats or dogs in infancy (aOR 0.60, 95% CI 0.42-0.85), decreased the risk of atopy at school age. The inverse association between farming and atopy was not explained by the sociodemographic factors, or by differences in conventional risk factors of atopy. Animal contacts explained partially, but not completely, the association. CONCLUSION: Higher frequency of animal contacts is one factor, but probably not the only one, explaining the inverse association of farming and atopy in children. The importance of early life exposures may have recently been over-emphasized, and current exposures discounted, when studying the risk factors of childhood atopy.

Agriculture↗
PubMed1991

Surface exclusion and molecular mobility may explain Vroman effects in protein adsorption.

Data on protein adsorption usually show that for increasing surface coverage the adsorption velocity decreases much faster than linearly. This contrasts to the classical Langmuir model with an adsorption velocity proportional to the number of unoccupied binding sites. It has been shown that this non-linearity may explain phenomena like transient adsorption of different proteins from a protein mixture or dilution-dependent changes in binding properties, collectively called Vroman effects. However, the molecular mechanisms explaining this non-linear behavior remain to be established. A Monte Carlo simulation model is presented that incorporates steric hindrance, lateral mobility and mutual interactions of adsorbed molecules. Experimental data on the adsorption kinetics of prothrombin and annexin V, a recently discovered anticoagulant protein, at phospholipid bilayers are analyzed with this model. A major conclusion is that the steep decline in adsorption rates for increasing surface coverage can be explained, without assuming repulsive forces between adsorbed molecules, as a surface exclusion effect combined with lateral mobility of adsorbed molecules. The fact that annexin V shows this effect to a much lesser degree than prothrombin is tentatively explained by clustering of adsorbed annexin V molecules. A qualitative effect of lateral mobility on the adsorption characteristics, predicted by the model, is confirmed in experiments in which the fluidity of the bilayers was manipulated.

Adsorption↗
PubMed2002

Contributions of 18 additional DNA sequence variations in the gene encoding apolipoprotein E to explaining variation in quantitative measures of lipid metabolism.

Apolipoprotein E (ApoE) is a major constituent of many lipoprotein particles. Previous genetic studies have focused on six genotypes defined by three alleles, denoted epsilon2, epsilon3, and epsilon4, encoded by two variable exonic sites that segregate in most populations. We have reported studies of the distribution of alleles of 20 biallelic variable sites in the gene encoding the ApoE molecule within and among samples, ascertained without regard to health, from each of three populations: African Americans from Jackson, Miss.; Europeans from North Karelia, Finland; and non-Hispanic European Americans from Rochester, Minn. Here we ask (1) how much variation in blood levels of ApoE (lnApoE), of total cholesterol (TC), of high-density lipoprotein cholesterol (HDL-C), and of triglyceride (lnTG) is statistically explained by variation among APOE genotypes defined by the epsilon2, epsilon3, and epsilon4 alleles; (2) how much additional variation in these traits is explained by genotypes defined by combining the two variable sites that define these three alleles with one or more additional variable sites; and (3) what are the locations and relative allele frequencies of the sites that define multisite genotypes that significantly improve the statistical explanation of variation beyond that provided by the genotypes defined by the epsilon2, epsilon3, and epsilon4 alleles, separately for each of the six gender-population strata. This study establishes that the use of only genotypes defined by the epsilon2, epsilon3, and epsilon4 alleles gives an incomplete picture of the contribution that the variation in the APOE gene makes to the statistical explanation of interindividual variation in blood measurements of lipid metabolism. The addition of variable sites to the genotype definition significantly improved the ability to explain variation in lnApoE and in TC and resulted in the explanation of variation in HDL-C and in lnTG. The combination of additional sites that explained the greatest amount of trait variation was different for different traits and varied among the six gender-population strata. The role that noncoding variable sites play in the explanation of pleiotropic effects on different measures of lipid metabolism reveals that both regulatory and structural functional variation in the APOE gene influences measures of lipid metabolism. This study demonstrates that resequencing of the complete gene in a sample of >/=20 individuals and an evaluation of all combinations of the identified variable sites, separately for each population and interacting environmental context, may be necessary to fully characterize the impact that a gene has on variation in related traits of a metabolic system.

Alleles↗
PubMed2005

The role of cognitive ability (intelligence) in explaining the association between socioeconomic position and health: evidence from the Whitehall II prospective cohort study.

Associations among cognitive ability, socioeconomic position, and health have been interpreted to imply that cognitive ability could explain social inequalities in health. The authors test this hypothesis by examining three questions: Is cognitive ability related to health? To what extent does it explain social inequalities in health? Do measures of socioeconomic position and cognitive ability have independent associations with health? Relative indices of inequality were used to estimate associations, using data from the Whitehall II study (baseline, 1985-1988), a British prospective cohort study (4,158 men and 1,680 women). Cognitive ability was significantly related to coronary heart disease, physical functioning, and self-rated health in both sexes and additionally to mental functioning in men. It explained some of the relation between socioeconomic position and health: 17% for coronary heart disease, 33% for physical functioning, 12% for mental functioning, and 39% for self-rated health. In analysis simultaneously adjusted for all measures of socioeconomic position, cognitive ability retained an independent association only with physical functioning in women. These results suggest that, although cognitive ability is related to health, it does not explain social inequalities in health.

Adult↗
PubMed2004

Can we explain why Brazilian babies are becoming lighter?

BACKGROUND: We tried to explain why a marked decrease in birthweight of 122 g occurred over a 15-year period in Ribeirão Preto, Brazil. METHODS: Factors reflecting biological, social, and health care characteristics (infant gender, parity, maternal age, marital status, type of hospital, maternal smoking, preterm birth, small for gestational age [SGA], and prenatal care) were assessed on 6711 newborns in 1978/1979 and 2838 in 1994 using multiple linear regressions. RESULTS: The birthweight distribution shifted to the left and the residual distribution of small preterm babies increased from 1.9% to 3.4%. Only marital status and preterm delivery would have decreased the difference in birthweight over time, explaining for each of them around 30 g of the 122 g. Increasing levels of attendance at antenatal care over time might have decreased the birthweight difference by 40 g. Maternal age and SGA explained little of the decreasing trend. Reductions in maternal smoking would have increased mean birthweight slightly. In stratified analysis the downward trend was more marked among mothers with high education (-202 g) and those delivered by caesarean section (-194 g). After adjusting for all those significant variables mean birthweight was still 74 g (95% CI: -97, -50 g) lower in 1994 than in 1978/1979. CONCLUSION: The trend could be explained in part by factors related to marital status that might reflect dysfunctional families in the Brazilian context and the preterm increase that might be associated with advances in medical technology. The high attendance at antenatal clinics or factors associated with it might have prevented a further decrease in birthweight. Our results may be compatible with the high economic development of Ribeirão Preto within Brazil, together with factors associated with its unfavourable lifestyle.

Adolescent↗
PubMed2000

Testing a BEIR-VI suggestion for explaining the lung cancer vs. radon relationship for U.S. counties.

The BEIR-VI Report suggests that the large discrepancy between the observed lung cancer rate vs. radon exposure relationship for U.S. counties, and the predictions of linear no-threshold theory, may be explained by a strong negative correlation between smoking intensity and radon exposure. It proposes a model for testing that suggestion. We apply that model to the detailed data for U.S. counties; analysis shows that even a perfect negative correlation explains little more than half of the discrepancy, and the largest not-implausible correlation can explain less than a quarter of the discrepancy. We then extend the BEIR-VI suggestion to include a strong negative correlation between both the prevalence of smoking and the intensity of smoking. The largest not-implausible correlations can explain no more than 30% of the discrepancy. It is concluded that the previous interpretation of these data, that linear no-threshold theory fails this test, is sustained.

Health Physics↗
PubMed2004

Behaviour partly explains educational differences in cancer incidence in the south-eastern Netherlands: the longitudinal GLOBE study.

Cancer morbidity and mortality vary among socio-economic groups. We investigated whether educational differences in behaviour could explain the variation in cancer incidence. In 1991, a postal questionnaire on socio-economic status, exposure variables, health and health-related behaviour was filled out by 18,973 participants (response rate 70.1%) of the longitudinal GLOBE study. Participants were followed and linked with the regional population-based Eindhoven Cancer Registry. Between 1991 and 1998 a total of 760 new tumours were found. The risk of cancer (all sites combined) was higher in the three quartiles of lower educational level compared with the highest educational level, odds ratios (ORs) varying from 1.25, 1.34, 1.27 to 1.00 from the lowest to the highest category, respectively (P=0.14). The relative risk (RR) for lung cancer for low versus high education was 2.7 [95% confidence interval (CI) 1.3-5.3]; adjustment for smoking, alcohol intake and physical activity decreased the risk to 1.6 (95% CI 0.8-3.3). Smoking alone explained 39% of the association, when alcohol intake and physical exercise were added to the model 61% of the effect was explained. In conclusion, a lower education is associated with increased cancer risks, which can be explained partly by behavioural factors.

Adolescent↗
PubMed2006

Explaining racial and ethnic disparities in health care.

OBJECTIVES: The substantial racial and ethnic disparities in access to and use of health services are well documented. A number of studies highlight factors such as health insurance coverage and socioeconomic differences that explain some of the differences between groups, but much remains unexplained. We build on this previous research by incorporating additional factors such as attitudes about health care and neighborhood characteristics, as well as separately analyzing different Hispanic subgroups. METHODS: We use the Oaxaca-Blinder regression-based method to decompose differences among racial and ethnic groups in 3 measures related to access, quantifying the portion explained by each of a number of underlying characteristics and the differences that remain unexplained. We use data from the 2000 and 2001 Medical Expenditure Panel Survey (MEPS), a nationally representative survey of the noninstitutionalized U.S. population. We link these data to detailed neighborhood characteristics from the Census Bureau and local provider supply data from the Health Services Resource Administration (HRSA). RESULTS: Consistent with earlier studies, we find insurance status and socioeconomic differences explain a significant part of the disparities. Additionally, neighborhood racial and ethnic composition account for a large portion of disparities in access, and language differences help explain observed disparities in the use-based access measure. However, much of the differences between racial and ethnic groups remain unexplained. We also found substantial variation in the level of disparities among different groups of Hispanics. CONCLUSIONS: Researchers and policymakers may need to broaden the scope of factors they consider as barriers to access if the goal of eliminating disparities in health care is to be achieved.

Adult↗
PubMed2006

Human development V: biochemistry unable to explain the emergence of biological form (morphogenesis) and therefore a new principle as source of biological information is needed.

Today's biomedicine builds on the conviction that biochemistry can explain the creation of the body, its anatomy and physiology. Unfortunately there are still deep mysteries strangely "fighting back" when we try to define and understand the organism and its creation in the ontogenesis as emerging from biochemistry. In analysing this from a theoretical perspective using a mathematical model focusing on the noise in complex chemical systems we argue that evolving biological structure cannot in principle be a product of chemistry. In this paper we go through the chemical gradient model and argue that this is not able to explain the ontogenesis. We discuss the used gradients as information carriers in chemical self-organizing systems and argue that by use of the "Turing structures" we are only able to modelling the mostly simple biological systems. The bio-chemical model is only able to model simple organization but not to explain the complexity of biological phenomena. We conclude that we seemingly have presented a formal proof (a NO-GO theorem) that the self-organizing chemical systems that are using chemical gradients are not able to explain complex biological matters as the ontogenesis. We need a fundamentally new, information-carrying principle to understand biological information and biological order.

Biochemical Phenomena↗
PubMed2006

Common variants of multiple genes that control reverse cholesterol transport together explain only a minor part of the variation of HDL cholesterol levels.

It is assumed that the combined effects of multiple common genetic variants explain a large part of variation of high-density lipoprotein cholesterol (HDL-C) plasma levels, but little evidence exists to corroborate this assumption. It was our objective to study the contribution of multiple common genetic variants of HDL-C-related genes to variation of HDL-C plasma levels. A well-characterized cohort of 546 Caucasian men with documented coronary artery disease was genotyped for common functional variants in genes that control reverse cholesterol transport: ATP-binding cassette transporter A1, apolipoprotein A-I and apolipoprotein-E, cholesteryl ester transfer protein, hepatic lipase, lecithin : cholesterol-acyl transferase, lipoprotein lipase, and scavenger receptor class B type 1. Multivariate linear regression showed that these variants, in conjunction, explain 12.4% (95% confidence interval: 6.9-17.9%) of variation in HDL-C plasma levels. When the covariates smoking and body mass index were taken into account, the explained variation increased to 15.3% (9.4-21.2%), and when 10 two-way interactions were incorporated, this percentage rose to 25.2% (18.9-31.5%). This study supports the hypothesis that multiple, mildly penetrant, but highly prevalent genetic variants explain part of the variation of HDL-C plasma levels, albeit to a very modest extent. Multiple environmental and genetic influences on HDL-C plasma levels still have to be elucidated.

ATP Binding Cassette Transporter 1↗