Social position and functional somatic disorders: The DanFunD study

Is reduced heart rate variability associated with functional somatic disorders? A cross-sectional population-based study; DanFunD

OBJECTIVES

It has been hypothesised that functional somatic disorders (FSD) could be initiated by sympathetic predominance in the autonomic nervous system as measured by low heart rate variability (HRV). Earlier studies on the association between HRV and FSD are small case-control studies hampered by selection bias and do not consider the great overlap between the various FSDs. The aim of the present study is to assess any associations between HRV and various FSDs and whether chronic stress confounds such an association.

DESIGN

A cross-sectional general population-based study.

SETTING

The Danish Study of Functional Somatic Disorders conducted 2013-2015 in 10 municipalities in the western part of Greater Copenhagen, Denmark.

PARTICIPANTS

A total of 6891 men and women aged 18-72 years were included in the analyses after exclusion of 602 persons with missing HRV data. Various delimitations of FSD (chronic fatigue, chronic widespread pain, irritable bowel and bodily distress syndrome) were identified by validated questionnaires and diagnostic interviews. HRV parameters in time and frequency domains were calculated from successive beat-to-beat heart rate (HR) data using the 'E-motion' HR monitor device during 7 min of supine rest. Chronic stress was assessed by Cohen's self-perceived stress scale.

OUTCOME MEASURES

Logistic regression analyses were used to calculate possible associations between the various delimitations of FSD and HRV adjusting for chronic stress.

RESULTS

Persons with FSD had a slightly higher mean HR and lower HRV as measured by time domain parameters, whereas associations with frequency domain parameters were not consistent. Adjusting for chronic stress attenuated associations slightly.

CONCLUSION

The study supports a sympathetic predominance in persons with FSD, which could not be entirely explained by chronic stress. However, it is not possible to conclude whether the association is a causal factor to or a consequence of FSD.

Lipid metabolism and functional somatic disorders in the general population. The DanFunD study

OBJECTIVES

Earlier studies on the association between plasma lipid profiles and functional somatic disorders (FSD) are mainly small case control studies hampered by selection bias and do not consider the great overlap between the various FSDs. The aim of the present study was to investigate the associations between various FSDs and plasma lipid profiles (total cholesterol, HDL cholesterol, non-HDL cholesterol and triglycerides) in a large, unselected population.

DESIGN

A cross-sectional general population-based study.

SETTING

The Danish Study of Functional Somatic Disorders (DanFunD) conducted in 2011-2015 in 10 municipalities in the western part of greater Copenhagen, Denmark.

PARTICIPANTS

A total of 8,608 men and women aged 18-76 years were included in the analyses. Various delimitations of FSD such as chronic fatigue, chronic widespread pain, irritable bowel, and bodily distress syndrome were measured using validated self-administrated questionnaires. Lipid parameters were measured from fasting plasma samples using colorimetric slide methods with Vitros 4600/5600 Ortho Clinical Diagnostics.

OUTCOME MEASURES

Logistic regression analyses were used to calculate possible associations between plasma lipids and the various delimitations of FSD. Associations are presented by OR (95% CI) and shown in boxplots.

RESULTS

We found a positive association between bodily distress syndrome and triglycerides and non-HDL cholesterol and a negative association with HDL-cholesterol, but no consistent association with total cholesterol. A similar pattern was observed for persons with chronic fatigue, and to some degree for persons with chronic widespread pain, whereas persons with irritable bowel did not show a clear association with the lipid profiles.

CONCLUSION

This is the first major study on plasma lipid profiles and FSD indicating an association between some delimitations of FSD and an unfavorable lipid profile. Due to the cross-sectional design, it cannot be determined whether the findings are consequences or determinants of FSD. Further studies-preferable prospective studies-are needed.

Neuroticism, perceived stress, adverse life events and self-efficacy as predictors of the development of functional somatic disorders: longitudinal population-based study (DanFunD)

BACKGROUND

Functional somatic disorder (FSD) is a unifying diagnosis that includes functional somatic syndromes such as irritable bowel, chronic widespread pain (CWP) and chronic fatigue. Several psychological factors are associated with FSD. However, longitudinal population-based studies elucidating the causal relationship are scarce.

AIMS

To explore if neuroticism, perceived stress, adverse life events (ALEs) and self-efficacy can predict the development of FSD over a 5-year period.

METHOD

A total of 4288 individuals who participated in the DanFunD baseline and 5-year follow-up investigations were included. FSD was established at both baseline and follow-up, with symptom questionnaires and diagnostic interviews. Neuroticism was measured with the short-form NEO Personality Inventory, perceived stress with the Cohen's Perceived Stress Scale, ALEs with the Danish version of the Cumulative Lifetime Adversity Measure and self-efficacy with the General Self-Efficacy Scale. Associations were investigated with multiple logistic regression models.

RESULTS

Perceived stress predicted incident FSD, irritable bowel, CWP and chronic fatigue (odds ratios: 1.04-1.17). Neuroticism predicted incident FSD and chronic fatigue (odds ratios: 1.03-1.16). ALEs predicted incident FSD, CWP and chronic fatigue (odds ratios: 1.06-1.18). An increase in perceived stress from baseline to follow-up was associated with incident FSD, irritable bowel, CWP and chronic fatigue (odds ratios: 1.05-1.22). Contrary, an increase in self-efficacy seemed to be a protective factor (odds ratios: 0.89-0.99).

CONCLUSIONS

High neuroticism, high perceived stress and a high number of ALEs are risk factors for the development of FSD. Particularly perceived stress seems to be an important contributor to the onset of FSD.

The association of vitamin K status with lung function and disease in a general population

Introduction

Matrix Gla protein (MGP) is an inhibitor of lung tissue calcification. The plasma level of dephosphorylated-uncarboxylated MGP (dp-ucMGP) is a biomarker of vitamin K status. The present study assessed whether lower vitamin K status (reflected by higher dp-ucMGP) was associated with lung function and lung disease/symptoms.

Methods

A general population sample of 4092 individuals, aged 24 to 77 years, underwent a health examination including questionnaires, spirometry and measurements of plasma dp-ucMGP. Associations of dp-ucMGP with lung function and self-reported disease/symptoms were estimated using regression models adjusted for age, sex and height. Associations were expressed as β-estimates or odds ratios (ORs) per doubling in dp-ucMGP.

Results

Lower vitamin K status (higher dp-ucMGP) was associated with lower forced expiratory volume in 1 s (FEV1) (98 mL; 95% CI: 54-141 mL) and lower forced vital capacity (FVC) (136 mL; 95% CI: 85-187 mL). Dp-ucMGP was not associated with the FEV1/FVC ratio (0.0 percentage points higher than the expected value; 95% CI: -1.0-1.0). Furthermore, lower vitamin K status was associated with COPD (OR 2.24, 95% CI: 1.53-3.27), wheezing (OR 1.81, 95% CI: 1.44-2.28) and asthma (OR 1.44, 95% CI: 1.12-1.83).

Conclusion

Lower vitamin K status was associated with lower ventilatory capacity (lower FEV1 and FVC), and with higher risk of self-reported asthma, COPD and wheezing. Vitamin K status was not associated with airflow obstruction (FEV1/FVC ratio).

Social economic factors and the risk of multiple chemical sensitivity in a Danish population-based cross-sectional study: Danish Study of Functional Disorders (DanFunD)

OBJECTIVES

Multiple chemical sensitivity (MCS) is a rare multisystem and poly-symptomatic disease characterised by a report of various somatic symptoms attributed to inhalation of volatile chemicals in usually harmless doses. The aim was to explore four selected social factors and the risk of MCS in the general Danish population.

DESIGN

A cross-sectional general population-based study.

SETTING

The Danish Study of Functional Disorders was conducted from 2011 to 2015 which included 9656 participants.

PARTICIPANTS

A total of 8800 participants were included in analyses after observations with missing data on exposure and/or outcome were excluded. A total of 164 cases fulfilled the questionnaire criteria for MCS. Of the 164 MCS cases, 101 reported no comorbid functional somatic disorder (FSD) and were included in a subgroup analysis. A total of 63 MCS cases fulfilled the criteria for at least one additional FSD, this subgroup was not included in further analysis. The remaining study population without MCS or any FSD were regarded as controls.

OUTCOME MEASURES

We used adjusted logistic regression to calculate OR and 95% CIs of MCS and MCS without FSD comorbidities for each social variable separately including education, employment, cohabitation and subjective social status.

RESULTS

We found an increased risk of MCS among the unemployed (OR: 2.95, 95% CI: 1.75 to 4.97), and a twofold increased risk of MCS among individuals with low subjective social status (OR: 2.00, 95% CI: 1.08 to 3.70). At the same time, 4 years or more of vocational training were protective of MCS. No significant associations were observed among MCS cases with no comorbid FSD.

CONCLUSION

Lower socioeconomic status was found to be associated with a higher risk of having MCS but not with MCS without FSD comorbidities. Due to the cross-sectional design of the study, we cannot determine whether social status is a determinant or a consequence of MCS.

Functional Neurologic Disorders, disorders to be managed by neurologists, or are neurologists wandering in a dangerous field with inadequate resources?

In recent years, some neurologists reconsidered their approach to Medically Unexplained Symptoms and proposed Functional Neurologic Disorders (FND) as a new entity, claiming that neurology could offer alternative treatment options to the psychotherapies provided in psychiatry settings. FNDs, for this purpose, should include only the disorders listed as Conversion from the Somatic Symptom and Related Disorders (SSRD) group. The present review analyzes the rationale of this position and challenges the arguments provided for its support. The review also discusses the systematization of these disorders as provided by public health systems. It outlines risks stemming from economic support and public funding uncertainty, given their negligible epidemiological dimensions resulting from the parcellation of SSRD. The review underlines the unresolved issue of Factitious Disorders, which are in the same SSRD category of the international classification but are, nonetheless, overlooked by the theoretical proponents of the FND entity. Comorbidity with other psychiatric disorders is also analyzed. We propose a model that supports the continuum between different SSRD conditions, including Factitious Disorders. The model is based on the emergence of feigned death reflex and deception from frontal lobe dysfunction. Finally, the paper summarizes the wealth of historical psychiatric and psychodynamic approaches and critical reviews. The study also puts in context the categorization and interpretation efforts provided by the most eminent researchers of the past century.

High Perceived Stress and Low Self-Efficacy are Associated with Functional Somatic Disorders: The DanFunD Study

Objective

Several psychological factors have been proposed to be associated with functional somatic disorders (FSD) including functional somatic syndromes, such as irritable bowel, chronic widespread pain, and chronic fatigue. However, large randomly selected population-based studies of this association are sparse. This study aimed to investigate the association between FSD and perceived stress and self-efficacy, respectively, and to investigate if FSD differed from severe physical diseases on these aspects.

Methods

This cross-sectional study included a random sample of the adult Danish population (n = 9656). FSD were established using self-reported questionnaires and diagnostic interviews. Perceived stress was measured with Cohen's Perceived Stress Scale and self-efficacy with the General Self-Efficacy Scale. Data were analysed with generalized linear models and linear regression models.

Results

FSD were associated with higher perceived stress and lower self-efficacy, especially for the multi-organ and the general symptoms/fatigue FSD types and for chronic fatigue. However, controlling for the personality trait neuroticism altered the associations with self-efficacy so it became insignificant. The analysis did not support an important interaction between perceived stress and self-efficacy on the likelihood of having FSD. Individuals with FSD presented levels of perceived stress that were not equal, ie higher, to those in individuals with severe physical diseases.

Conclusion

FSD were positively associated with perceived stress and negatively associated with self-efficacy. Our study may point to stress being part of the symptomatology of FSD. This underlines the severity of having FSD and stresses the relevance of the resilience theory in the understanding of the condition.

Neuroticism and adverse life events are important determinants in functional somatic disorders: the DanFunD study

Several psychological factors have been proposed to be associated with functional somatic disorders (FSD). However, large population-based studies investigating the importance of both personality and adverse life events (ALE) are sparse. This study aimed to investigate the association between FSD and neuroticism and the accumulated number of ALE, respectively. This cross-sectional study included a random sample of the adult Danish population (N = 7493). FSD were established by means of self-reported questionnaires and diagnostic interviews. Neuroticism was measured with the Danish version of the short-form NEO Personality Inventory. ALE were measured with the Danish version of the Cumulative Lifetime Adversity Measure. Strong positive associations were found between neuroticism and FSD, and ALE and questionnaire-based FSD. For interview-based FSD, strong positive associations were found for FSD, multi-organ type, and for the subtype of the general symptoms. The level of self-efficacy did not modify these associations, and no moderating effect of neuroticism and ALE in combination on the probability of having FSD was found. FSD were strongly associated with both neuroticism and the accumulated number of ALE, and these associations were not modified by self-efficacy. In combination, neuroticism and ALE did not have a moderating effect on the probability of having FSD.

Examine the public health impacts of functional somatic disorders using the DanFunD study

Background: Persistent physical symptoms (e.g. pain, fatigue) are prevalent in the population and some persons may develop a functional somatic disorder (FSD). We still need to explore the limits between general bodily sensations and FSD, and great controversies exist as regard delimitation, occurrence, risk factors, prognosis, and costs of FSD in the general population. This is mainly due to the lack of focused, sufficient powered, population-based epidemiological studies. Material and Methods: The DanFunD study is the largest focused population-based study on FSD and has the potential to answer these crucial questions regarding the FSD disorders. DanFunD has its origin in the Copenhagen area of Denmark and was initiated in 2009 by an interdisciplinary team of researchers including basic scientists, clinical researchers, epidemiologists, and public health researchers. A population-based cohort of nearly 10,000 people have filled in detailed questionnaires, gone through a thorough health examination, and a biobank is established. The cohort was re-examined after five years. Results:The prevalence of FSD in the Danish population is about 10-15% and is twice as common in women as in men. Persons with FSD report impaired daily activities and low self-perceived health, which qualifies FSD as a major public health problem. The research plan to unravel the risk factors for FSD employs a bio-psycho-social approach according to a detailed plan. Preliminary results are presented, and work is in progress. Likewise, plans for assessing prognosis and health care costs are provided. Conclusion: We invite researchers in the field to collaborate on this unique data material.

Development and Validation of the Weighted Index for Childhood Adverse Conditions (WICAC)

BACKGROUND

Adverse experiences in childhood are a major public health concern, promoting social inequality in health through biopsychosocial mechanisms. So far, no known measures comprehend the complexity and variations of severity of adverse events. This study aims to develop and validate a new index: the Weighted Index for Childhood Adverse Conditions (WICAC).

METHODS

The population consists of 7493 randomly invited men and women aged 18-72 years. Data were collected in 2012-2015 as part of the Danish Study of Functional Disorders (DanFunD). Content and construct validation of the WICAC was performed with the hypothesis testing of multiple biopsychosocial outcomes: cardiovascular disease, cancer, poor health, back pain, BMI, obesity, anxiety, depression, low vitality, subjective social status, lower education, smoking, and alcohol consumption. Data were analysed with binominal and linear regression models with risk ratios (RR) and mean differences (MD).

RESULTS

Content validation is fitting for WICAC. The strongest associations observed were for most severe adversity: Poor Health RR = 2.16 (1.19-2.91), Anxiety RR = 3.32 (2.32-4.74), Heavy Drinking RR = 4.09 (1.85-9.04), and Subjective Social Status MD = -0.481 (-0.721-(-0.241)). Similar results were found for the remaining outcomes. Discriminative validation was undecided.

CONCLUSIONS

WICAC is an adequate instrument for measuring cumulative adverse life events in childhood and adolescence for research purposes.

Physiological Health and Physical Performance in Multiple Chemical Sensitivity-Described in the General Population

Multiple chemical sensitivity (MCS) is a multifactorial somatic disorder characterized by physical reactions triggered by even extremely low levels of different airborne chemicals. In most individuals with MCS, these reactions have substantial negative impact on social, occupational, and everyday life often including limited or no engagement in physical activities. The aim of this study was to explore associations between MCS and objective measurements of anthropometry, cardiorespiratory health, and physical performance. From the Danish population-based cohort DanFunD counting 9656 participants aged 18–76 years, 1.95% (n = 188) were categorized as MCS individuals (MCS All). Of those 188, 109 participants were subcategorized as having MCS without functional somatic disorders (FSD) (MCS with no comorbid FSD). The remaining study population without any FSD were regarded controls. We used adjusted multiple linear regression analyses to evaluate associations between MCS and anthropometry, cardiorespiratory fitness, and physical performance. Compared with the general population, MCS All had less optimal body composition, increased risk of obesity, impaired cardiorespiratory fitness, and physical performance which was not seen in MCS with no comorbid FSD. MCS individuals may be inhibited to maintain an active lifestyle which can increase risk of obesity and consequently have negatively impact on general health, which may not be the case among MCS with no comorbid FSD.

Insulin Resistance Is Associated with Multiple Chemical Sensitivity in a Danish Population-Based Study-DanFunD

Multiple chemical sensitivity (MCS) is a multisystem syndrome, and limited knowledge of its pathophysiology exists. Based on the population-based Danish cohort DanFunD, this study investigated metabolic health in people with MCS compared to individuals who did not have MCS. From 9656 cohort participants aged 18–76 years old, 1.95% were categorized as MCS individuals with comorbid functional somatic disorders (MCS +FSD, n = 188), and 1.13% were categorized as MCS without functional somatic disorders (MCS ÷FSD, n = 109). MCS was characterized based on three criteria: the experience of symptoms upon exposure to common odors and airborne chemicals, symptoms related the central nervous systems and others organ symptoms, and significant impact on every day, social, and occupational life. The remaining study population without MCS or any other functional somatic disorders were regarded as controls. We used adjusted multiple linear regression with link-function to evaluate the associations between lipid and glucose metabolism markers and MCS. We also tested the odds ratio of metabolic syndrome in MCS. Results did not point to statistically significant associations between lipid biomarkers or metabolic syndrome and both MCS groups compared to the controls. We found that MCS individuals may be more insulin resistant and that MCS ÷ FSD may have an impaired glucose metabolism when compared to controls.

Conditioned pain modulation and pain sensitivity in functional somatic disorders: The DanFunD study

Background

Disrupted pain regulation has been proposed as a component in functional somatic disorders (FSD). The objective of this study was to examine a general population sample, encompassing three delimitations of FSD while assessing pain sensitivity and conditioning pain modulation (CPM).

Methods

Pressure pain thresholds (PPTs) at the tibialis and trapezius muscles were recorded at baseline. During cold pressor stimulation of the hand, the tibialis PPTs were re‐assessed and the difference from baseline measures defined the CPM effect. Participants (n = 2,198, 53% females) were randomly selected from the adult Danish population. FSD was established by self‐reported symptom questionnaires.

Results

With a few exceptions, only weak associations were seen between PPTs and CPM in cases with FSD (p > .1). A high PPT was associated with lower odds of having multi‐organ bodily distress syndrome (OR^{PPT trapezius}: 0.66, 95% CI: 0.49–0.88, p = .005), with the symptom profile characterized by all symptoms (OR^{PPT trapezius}: 0.72, 95% CI: 0.58–0.90, p = .003 and OR^{PPT tibialis}: 0.75, 95% CI: 0.62–0.91, p = .004), and with multiple chemical sensitivity (OR^{PPT trapezius}: 0.81, 95% CI: 0.67–0.97, p = .022). High CPM was associated with high odds of having irritable bowel (OR^{CPM relative}: 1.22, 95% CI: 1.04–1.43, p = .013 and OR^{CPM absolute} = 2.66, 95% CI: 1.07–6.45, p = .033).

Conclusion

However, only PPT measured over the trapezius muscle were still significant after correction for multiple testing for the symptom profile characterized by all symptoms. Findings from this study do not support altered pain regulation in questionnaire‐based FSD which is in contrast with the existing presumption. Further epidemiological studies in this field are needed.

Significance

Disrupted pain regulation as measured by abnormal pain thresholds has been hypothesized as a central mechanism in Functional Somatic Disorders (FSD). The hypothesis has been raised in clinical setting where patients presented subjective and objective features of hypersensitivity. The present population‐based study does not support this notion. This points to the importance of further studies into the underlying pathophysiology mechanisms of FSD.