Antidepressant Exposure and DNA Methylation: Insights from a Methylome-Wide Association Study

Importance

Understanding antidepressant mechanisms could help design more effective and tolerated treatments.

Objective

Identify DNA methylation (DNAm) changes associated with antidepressant exposure.

Design

Case-control methylome-wide association studies (MWAS) of antidepressant exposure were performed from blood samples collected between 2006-2011 in Generation Scotland (GS). The summary statistics were tested for enrichment in specific tissues, gene ontologies and an independent MWAS in the Netherlands Study of Depression and Anxiety (NESDA). A methylation profile score (MPS) was derived and tested for its association with antidepressant exposure in eight independent cohorts, alongside prospective data from GS.

Setting

Cohorts; GS, NESDA, FTC, SHIP-Trend, FOR2107, LBC1936, MARS-UniDep, ALSPAC, E-Risk, and NTR.

Participants

Participants with DNAm data and self-report/prescription derived antidepressant exposure.

Main Outcomes and Measures

Whole-blood DNAm levels were assayed by the EPIC/450K Illumina array (9 studies, N exposed = 661, N unexposed = 9,575) alongside MBD-Seq in NESDA (N exposed = 398, N unexposed = 414). Antidepressant exposure was measured by self- report and/or antidepressant prescriptions.

Results

The self-report MWAS (N = 16,536, N exposed = 1,508, mean age = 48, 59% female) and the prescription-derived MWAS (N = 7,951, N exposed = 861, mean age = 47, 59% female), found hypermethylation at seven and four DNAm sites (p < 9.42x10 -8 ), respectively. The top locus was cg26277237 ( KANK1, p self-report = 9.3x10 -13 , p prescription = 6.1x10 -3 ). The self-report MWAS found a differentially methylated region, mapping to DGUOK-AS1 ( p adj = 5.0x10 -3 ) alongside significant enrichment for genes expressed in the amygdala, the "synaptic vesicle membrane" gene ontology and the top 1% of CpGs from the NESDA MWAS (OR = 1.39, p < 0.042). The MPS was associated with antidepressant exposure in meta-analysed data from external cohorts (N studies = 9, N = 10,236, N exposed = 661, f3 = 0.196, p < 1x10 -4 ).

Conclusions and Relevance

Antidepressant exposure is associated with changes in DNAm across different cohorts. Further investigation into these changes could inform on new targets for antidepressant treatments.

3 Key Points

Question: Is antidepressant exposure associated with differential whole blood DNA methylation?Findings: In this methylome-wide association study of 16,536 adults across Scotland, antidepressant exposure was significantly associated with hypermethylation at CpGs mapping to KANK1 and DGUOK-AS1. A methylation profile score trained on this sample was significantly associated with antidepressant exposure (pooled f3 [95%CI]=0.196 [0.105, 0.288], p < 1x10 -4 ) in a meta-analysis of external datasets. Meaning: Antidepressant exposure is associated with hypermethylation at KANK1 and DGUOK-AS1 , which have roles in mitochondrial metabolism and neurite outgrowth. If replicated in future studies, targeting these genes could inform the design of more effective and better tolerated treatments for depression.

Remote Assessment of Disease and Relapse in Major Depressive Disorder (RADAR-MDD): Recruitment, retention, and data availability in a longitudinal remote measurement study

Introduction

Major Depressive Disorder (MDD) is prevalent, often chronic, and requires ongoing monitoring of symptoms to track response to treatment and identify early indicators of relapse. Remote Measurement Technologies (RMT) provide an exciting opportunity to transform the measurement and management of MDD, via data collected from inbuilt smartphone sensors and wearable devices alongside app-based questionnaires and tasks.

Objectives

To describe the amount of data collected during a multimodal longitudinal RMT study, in an MDD population.

Methods

RADAR-MDD is a multi-centre, prospective observational cohort study. People with a history of MDD were provided with a wrist-worn wearable, and several apps designed to: a) collect data from smartphone sensors; and b) deliver questionnaires, speech tasks and cognitive assessments and followed-up for a maximum of 2 years.

Results

A total of 623 individuals with a history of MDD were enrolled in the study with 80% completion rates for primary outcome assessments across all timepoints. 79.8% of people participated for the maximum amount of time available and 20.2% withdrew prematurely. Data availability across all RMT data types varied depending on the source of data and the participant-burden for each data type. We found no evidence of an association between the severity of depression symptoms at baseline and the availability of data. 110 participants had > 50% data available across all data types, and thus able to contribute to multiparametric analyses.

Conclusions

RADAR-MDD is the largest multimodal RMT study in the field of mental health. Here, we have shown that collecting RMT data from a clinical population is feasible.

Disclosure

No significant relationships.

Chronological and biological age: Why relevant for psychiatrists?

Introduction

Depression is the mental disorder with the largest disease burden impact. That is due to its high prevalence, chronicty, early onset but also due to its impact on various aging-related somatic morbidities and mortality. This talk will describes to what extent depression characteristics are related to chronologial and biological aging patterns.

Methods

Data will be shown from the Netherlands Study of Depression and Anxiety (NESDA, www.nesda.nl). In this study, a large cohort of over 3000 individuals (18-65 years), among which over 1200 with a DSM-based major depressive disorder (MDD), are now followed for 9 years. The association between depression characteristics and chronological and biological age will be described. Biological age was determined at various biological system-levels, including telomere length, epigenetics, transcriptomics, metabolomics and proteomics.

Results

Older persons with a current MDD do not differ in overall disease severity as compared to younger persons with a current MDD. However, older depressed persons do differ in the types of symptoms they experience (more neurovegetative, somatic symptoms and less mood symptoms) and in their chronic course (with twice more chronicity in the oldest depressed persons compare to the younges depressed persons). At all biological system-levels, there was evidence for more advaned biological aging among persons with depression. This was not differential across chronological age groups. Discussion: Findings suggest that depression characteristics are linked to both chronological and biological age. It will be discussed what this could mean for clinical practice and intervention.

Disclosure

No significant relationships.

Toxoplasma gondii seropositivity in patients with depressive and anxiety disorders

Introduction

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite that is estimated to be carried by one-third of the world population. While evidence has been found for a relationship between T. gondii infection and schizophrenia, its relationship with other psychiatric disorders like depressive and anxiety disorders shows inconsistent results.

Objectives

The aim of the present study was to examine whether T. gondii seropositivity is associated with affective disorders, as well as with aggression reactivity and suicidal thoughts.

Methods

In the Netherlands Study of Depression and Anxiety (NESDA), T. gondii antibodies were assessed in patients with current depressive (n=133), anxiety (n=188), comorbid depressive and anxiety (n=148), and remitted disorders (n=889), as well as in healthy controls (n=373) based on DSM-IV criteria. Seropositivity was analyzed in relation to disorder status, aggression reactivity and suicidal thoughts using multivariate analyses of covariance and regression analyses.

Results

Participants were on average 51.2 years (SD = 13.2), and 64.4% were female. Seropositivity was found in 673 participants (38.9%). A strong positive association between T. gondii seropositivity and age was observed. No significant associations were found between T. gondii seropositivity and disorder status, aggression reactivity and suicidal thoughts. The adjusted odds ratio (OR) for any remitted disorder versus controls was 1.13 (95% CI: 0.87-1.49), and for any current disorder versus controls was 0.94 (95% CI: 0.69- 1.28).

Conclusions

No evidence was found for a relationship between affective disorders and T. gondii infection

Disclosure

No significant relationships.

The opportunities and obstacles of studying telomere length as a biological aging marker in psychiatry

Aging can be described as the life-long accumulation of damage to the tissues, cells, and molecules of the body. One of the most widely used markers to study biological aging is telomere length. Telomeres are non-coding DNA structures located at the ends of chromosomes that become progressively shorter with age. Research in the past decade showed that persons with psychiatric disorders such as major depressive disorder, anxiety disorder or posttraumatic stress disorder on average have shorter telomeres, which might help explain the high levels of somatic morbidity in these patients. While telomere length is an elegant aging biomarker, reflecting a biological process in most living species, there are also some challenges. In human studies, the between-person variation is large and shortened telomeres showed not to be specific to psychiatric diagnosis but rather to a multitude of psychological and physiological stressors. Telomere length might therefore not be a diagnostic marker. It could, nonetheless, be an interesting target for pharmacological, psychological or exercise treatment. If persons with psychiatric disorders age biologically faster, to what extend can this be process be halted or even reversed with successful treatment? Other opportunities and obstacles of studying telomere length as a biological aging marker in psychiatry will be discussed in this session.

Brain aging in major depressive disorder

Depression and anxiety are common and often comorbid mental health disorders that represent risk factors for aging-related conditions. Brain aging has shown to be more advanced in patients with Major Depressive Disorder (MDD). Here, we extend prior work by investigating multivariate brain aging in patients with MDD and/or anxiety disorders and examine which factors contribute to older appearing brains. Adults aged 18-57 years from the Netherlands Study of Depression and Anxiety underwent structural MRI. A pre-trained brain age prediction model based on >2,000 samples from the ENIGMA consortium was applied to obtain brain-predicted age differences (brain-PAD, predicted brain age minus chronological age) in 65 controls and 220 patients with current MDD and/or anxiety. Brain-PAD estimates were associated with clinical, somatic, lifestyle, and biological factors. After correcting for antidepressant use, brain-PAD was significantly higher in MDD (+2.78 years, Cohen’s d=0.25, 95% CI -0.10-0.60) and anxiety patients (+2.91 years, Cohen’s d=0.27, 95% CI -0.08-0.61), compared to controls. There were no significant associations with lifestyle or biological stress systems. A multivariable model indicated unique contributions of higher severity of somatic depression symptoms (b=4.21 years per unit increase on average sum score) and antidepressant use (-2.53 years) to brain-PAD. Advanced brain aging in patients with MDD and anxiety was most strongly associated with somatic depressive symptomatology. We also present clinically relevant evidence for a potential neuroprotective antidepressant effect on the brain-PAD metric that requires follow-up in future research.

The Clinical Course of Depression: Chronicity is the Rule Rather than the Exception

Introduction

Major depressive disorder (MDD) is often considered an episodic disorder. However, literature might underestimate the chronicity of MDD since results depend on follow-up duration and the extent to which psychiatric co-morbidity is taken into account.

Aim

To determine, whether MDD should be considered an episodic or chronic disorder.

Objective

To examine the 6 year course of MDD, incorporating data of multiple time points and taking common psychiatric comorbidities into account.

Methods

Data were from 903 patients with current MDD at baseline in the Netherlands study of depression and anxiety, with subsequent data from 2 year, 4 year and 6 year follow-up. Four course trajectories were created taking all information during follow-up into account classifying patients as (1) recovered, (2) recurrent without chronic episodes, (3) recurrent with chronic episodes or (4) consistently chronic. A chronic episode was defined as having symptoms consistently over 2 years.

Results

The recovery rate of MDD was 58% at 2 year follow-up but looking at 6 year follow-up and taking into account co-morbid dysthymia, (hypo) mania and anxiety disorders reduced this recovery rate to 17%. Moreover, more than half of the patients experienced chronic episodes.

Conclusions

Longitudinal data of this psychiatric cohort study showed that full recovery is the exception rather than the rule. MDD follows a chronic course and, moreover, persons are prone to switch to other psychiatric disorders.

Telomere Length and Depressive and Anxiety Disorders: Longitudinal Associations and Underlying Mechanisms

Many psychiatric disorders have been associated with increased risk of mortality and various aging-related somatic diseases. In addition to unhealthy lifestyles, also various stress-related physiological processes likely play a role in explaining these detrimental health consequences of psychiatric disorders. The impact could be visible at the cellular level, with psychiatric patients presenting more signals of physiological aging for instance as determined by measuring telomere length. In this talk we will first highlight the current state-of-the art evidence that various psychiatric conditions, including e.g. depression, anxiety and PTSD, are associated with shorter telomere length. Second, we will provide results from the Netherlands Study of depression and anxiety (n = 2981) that tested longitudinal associations using 6 year data on psychiatric status and telomere length. These results indicate that the association between depressive and anxiety disorders with telomere length is stable over time, and doesn’t show many dynamic associations. Finally, in the same study we have also tested to what extent lifestyle and dysregulations of physiological stress systems such as the immune, HPA-axis and autonomic nervous systems are partly responsible for the observed shorter telomere length in depressed or anxious patients. Results indicate that especially smoking behavior and systemic inflammation partly contribute to the shorter telomere length, but can’t completely explain found associations.

In sum, this talk will highlight the current state-of-evidence for an association between various psychiatric conditions with shorter telomere length, and will provide insights into its dynamics and its contributing mechanisms.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Depression and its Somatic Consequences: Allostatic Load as the Connecting Link

Stress-related psychiatric disorders, such as depressive and anxiety disorders, have been associated with increased risk of overall mortality as well as with the onset of various aging-related somatic diseases. In addition to unhealthy lifestyles and poorer (self) care, various stress-related physiological processes likely contribute to these detrimental health consequences of psychiatric disorders. Considering the fact that the impact of stress-related disorders is visible on many different somatic health outcomes, it is unlikely that contributing biological systems are very specific. In fact, it is likely that multiple dysregulations of stress systems, including the immune, HPA-axis and autonomic nervous systems, but also various general proteomic or metabolomic pathways are involved. The concept of Allostatic Load (AL) emphasizes the presence of a multi-system physiological dysregulation.

In this talk I will summarize what the evidence is for somatic health consequences of psychiatric conditions, with depression as an important example. Subsequently, I will provide an overview of the various stress systems that are dysregulated in depressed patients. In addition, I will provide empirical data from the Netherlands Study of Depression and Anxiety (n = 2981) that illustrate that there is evidence that depressed patients are especially at risk for a dysregulation in multiple physiological stress systems. I will also illustrate how such a state of AL can impact on basis cellular aging indicators like telomere length and epigenetic age.

In sum, this talk will highlight the current state-of-evidence for an association between depressions with the onset of many adverse somatic health outcomes, and will provide insight into the contributing role of a multisystem physiological dysregulation.

Disclosure of interest

The author has not supplied his declaration of competing interest.

Oxidative DNA damage is associated with antidepressant use, not depression or anxiety disorders

Introduction

Oxidative stress has been implicated in the pathophysiology of depression and anxiety disorders and may be influenced by antidepressant use.

Objectives

This study investigated the association of oxidative stress, measured by plasma levels of F2-isoprostanes and 8-hydroxy-2′-deoxyguanosine (8-OHdG), reflecting oxidative lipid and DNA damage respectively, with major depressive disorder (MDD), generalized anxiety disorder, social phobia, panic disorder, agoraphobia and antidepressant use in a large cohort.

Methods

Data was derived from the Netherlands Study of Depression and Anxiety including patients with current (n = 1641) or remitted (n = 610) MDD and/or anxiety disorder(s) (of which n = 709 antidepressant users) and 633 controls. Diagnoses were established with the Composite Interview Diagnostic Instrument. Plasma 8-OHdG and F2-isoprostanes were measured using UHPLC-MS/MS. ANCOVA was performed adjusting for sampling, sociodemographic, health and lifestyle variables.

Results

F2-isoprostanes did not differ between controls and patients, or by antidepressant use. Patients (current or remitted) using antidepressants had lower 8-OHdG (adjusted mean 38.3 pmol/L) compared to patients (current or remitted) without antidepressants (44.7 pmol/L) and controls (44.9 pmol/L, P < 0.001; Cohen's d 0.26). Findings for 8-OHdG were similar over all disorders and all antidepressant types (SSRIs, TCAs, SNRIs; P < 0.001).

Conclusion

Contrary to previous findings this large-scale study did not find increased oxidative stress measured by F2-isoprostanes or 8-OHdG in MDD or anxiety disorders. 8-OHdG levels were lower in antidepressant users, which suggests antidepressants may have antioxidant properties.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Gene transcripts associated with muscle strength: a CHARGE meta-analysis of 7,781 persons

Lower muscle strength in midlife predicts disability and mortality in later life. Blood-borne factors, including growth differentiation factor 11 (GDF11), have been linked to muscle regeneration in animal models. We aimed to identify gene transcripts associated with muscle strength in adults. Meta-analysis of whole blood gene expression (overall 17,534 unique genes measured by microarray) and hand-grip strength in four independent cohorts (n = 7,781, ages: 20-104 yr, weighted mean = 56), adjusted for age, sex, height, weight, and leukocyte subtypes. Separate analyses were performed in subsets (older/younger than 60, men/women). Expression levels of 221 genes were associated with strength after adjustment for cofactors and for multiple statistical testing, including ALAS2 (rate-limiting enzyme in heme synthesis), PRF1 (perforin, a cytotoxic protein associated with inflammation), IGF1R, and IGF2BP2 (both insulin like growth factor related). We identified statistical enrichment for hemoglobin biosynthesis, innate immune activation, and the stress response. Ten genes were associated only in younger individuals, four in men only and one in women only. For example, PIK3R2 (a negative regulator of PI3K/AKT growth pathway) was negatively associated with muscle strength in younger (<60 yr) individuals but not older (≥ 60 yr). We also show that 115 genes (52%) have not previously been linked to muscle in NCBI PubMed abstracts. This first large-scale transcriptome study of muscle strength in human adults confirmed associations with known pathways and provides new evidence for over half of the genes identified. There may be age- and sex-specific gene expression signatures in blood for muscle strength.

Childhood maltreatment modifies the relationship of depression with hippocampal volume

BACKGROUND

Childhood maltreatment (CM) may modify the relationship between major depressive disorder (MDD) and hippocampal volume reduction. To disentangle the impact of MDD and CM on hippocampal volume we investigated the association between MDD and hippocampal volume in persons with and without a history of CM in two independent cohorts.

METHOD

We used data of 262 participants from the Netherlands Study of Depression and Anxiety (NESDA) (mean age 37 years, 32% male) and 636 participants from the SMART-Medea study (mean age 61 years, 81% male). In both studies a 12-month diagnosis of MDD and CM were assessed using a diagnostic interview. Hippocampal volume was measured in NESDA using FreeSurfer software on 3-T magnetic resonance (MR) images and in SMART it was manually outlined on 1.5-T MR images. With analysis of covariance adjusted for intracranial volume, age, gender and lifestyle factors we estimated the effects of MDD and CM on hippocampal volume.

RESULTS

In both cohorts CM was not significantly associated with hippocampal volume. After pooling the data MDD was associated with smaller hippocampal volume (B = -138.90 mm(3), p = 0.05) and the interaction between MDD and CM reached significance (p = 0.04); in participants with CM, MDD was related to smaller hippocampal volume (NESDA: B = -316.8 mm(3), p = 0.02; SMART: B = -407.6, p = 0.046), but not in participants without CM (p > 0.05).

CONCLUSIONS

Our study shows that in two independent cohorts, particularly in individuals with CM, a diagnosis of MDD is related to smaller hippocampal volume. Prospective studies are needed to further determine through which mechanism CM may amplify the relationship between MDD and hippocampal volume.

A K(ATP) channel gene effect on sleep duration: from genome-wide association studies to function in Drosophila

Humans sleep approximately a third of their lifetime. The observation that individuals with either long or short sleep duration show associations with metabolic syndrome and psychiatric disorders suggests that the length of sleep is adaptive. Although sleep duration can be influenced by photoperiod (season) and phase of entrainment (chronotype), human familial sleep disorders indicate that there is a strong genetic modulation of sleep. Therefore, we conducted high-density genome-wide association studies for sleep duration in seven European populations (N=4251). We identified an intronic variant (rs11046205; P=3.99 × 10(-8)) in the ABCC9 gene that explains ≈5% of the variation in sleep duration. An influence of season and chronotype on sleep duration was solely observed in the replication sample (N=5949). Meta-analysis of the associations found in a subgroup of the replication sample, chosen for season of entry and chronotype, together with the discovery results showed genome-wide significance. RNA interference knockdown experiments of the conserved ABCC9 homologue in Drosophila neurons renders flies sleepless during the first 3 h of the night. ABCC9 encodes an ATP-sensitive potassium channel subunit (SUR2), serving as a sensor of intracellular energy metabolism.

Chronic medical conditions mediate the association between depression and cardiovascular disease mortality

Purpose

To determine whether chronic medical conditions mediate the association between depression and cardiovascular disease (CVD) mortality.

Methods

Data analyzed were from 6,394 subjects aged 25–74 years who participated in extensive health examinations in the NHEFS conducted between 1971 and 1975 and follow-up studies to 1992. CVD mortality was the endpoint. Depression predictors were clinically significant depressive symptoms at baseline by the GWB-D, and/or at 1982–84 by the CES-D (‘baseline’, ‘new’, or ‘twice’ depression). Chronic conditions were prevalent/incident high blood pressure, diabetes, and nonfatal CVD by examination and/or self-report. Mediation effects were assessed by stepwise adjustments of covariates and additive interactions in competing-risks regression models (accounting for other mortality causes) and logit models.

Results

Baseline, new, and twice depression were significant predictors of CVD mortality in competing-risks models adjusted for demographics (HRs 1.3, 1.4, and 2.0), but effects were progressively weakened and became non-significant after adjustment for lifestyle factors, prevalent and incident medical conditions, respectively. CVD mortality risk was 80% higher for depression plus incident nonfatal CVD than without (HR 4.0 vs. 3.2, additive interaction), and mediation effects of depression via chronic medical conditions (particularly via incident nonfatal CVD) increased the risk by 2 to 11% in logit models, independent of all covariates.

Conclusions

Several levels of evidence suggest that the association between depression and CVD mortality is partially mediated by prevalent/incident chronic medical conditions, as well as unhealthy lifestyle behaviors. Patients presenting with clinically significant depressive symptoms, particularly if persistent, should be assessed for both chronic conditions and lifestyle risk factors.

Depression is Associated with Decreased 25-hydroxyvitamin-D and Increased Parathyroid Hormone Levels in Old Age

About 13 percent of older individuals have symptoms of depression, and other researchers have speculated that vitamin D may be linked to depression. Underlying causes of vitamin D deficiency such as less sun exposure as a result of decreased outdoor activity, different housing or clothing habits and decreased vitamin intake may be secondary to depression, but depression may also be the consequence of poor vitamin D status. Moreover, poor vitamin D status causes an increase in serum parathyroid hormone levels. Overactive parathyroid glands are frequently accompanied by symptoms of depression that disappear after treatment of the condition. We recently measured blood levels of vitamin D and parathyroid hormone and assessed symptoms of depression among 1,282 community residents age 65 to 95 and found a strong decrease in vitamin D level and increase in parathyroid hormone level (Hoogendijk et al., Arch Gen Psychiat 2008;65(5):508-512). This finding may be important to patients because both low blood vitamin D levels and high parathyroid hormone levels can be treated with higher dietary intake of vitamin D or calcium and increased sunlight exposure. Moreover light treatment has been used successfully to treat seasonal affective disorder. Taking these two lines of studies together, sunlight may have an antidepressant effect via the eye-biological clock tract and via the skin-vitamin D-tract. Interestingly, the biological clock is located in the hypothalamus, where vitamin D receptor is most abundant.

Endogenous sex hormone levels and risk of cognitive decline in an older biracial cohort

BACKGROUND

Older women treated with conjugated estrogens may have an increased risk of dementia, but the effect of naturally occurring sex hormones on cognition is not certain.

METHODS

Bioavailable estradiol and free testosterone level were obtained from 792 (55% men, 51% black) participants. We assessed cognition with the Modified Mini-Mental State Examination (3MS), Selective Reminding Test (SRT) and CLOX 1 at baseline and 2 years later.

RESULTS

Women in the lowest estradiol tertile were more likely than those in the highest tertile to decline (> or = 1.0 S.D. of change) on 3MS (25% versus 9%, adjusted odds ratio [OR] = 3.9; 95% confidence interval [CI] = 1.6-9.6) and on SRT (28% versus 12%, adjusted OR [95% CI] = 3.3 [1.4-7.9]) but not CLOX 1. There was a borderline association between low estradiol tertile and decline on SRT in men (22% versus 14%, adjusted OR [95% CI] = 1.9 [0.9-3.9]). Testosterone level was not associated with decline in cognition in either men or women. Findings did not differ by race.

CONCLUSIONS

Older women with low estradiol levels were more likely to experience decline in global cognitive function and verbal memory, and a similar trend was observed for verbal memory in men. This supports the hypothesis that endogenous sex hormones may play an important role in the maintenance of cognitive function in older adults.

Serum IL-6 level and the development of disability in older persons

BACKGROUND

The serum concentration of interleukin 6 (IL-6), a cytokine that plays a central role in inflammation, increases with age. Because inflammation is a component of many age-associated chronic diseases, which often cause disability, high circulating levels of IL-6 may contribute to functional decline in old age. We tested the hypothesis that high levels of IL-6 predict future disability in older persons who are not disabled.

METHODS

Participants at the sixth annual follow-up of the Iowa site of the Established Populations for Epidemiologic Studies of the Elderly aged 71 years or older were considered eligible for this study if they had no disability in regard to mobility or in selected activities of daily living (ADL), and they were re-interviewed 4 years later. Incident cases of mobility-disability and of ADL-disability were identified based on responses at the follow-up interview. Measures of IL-6 were obtained from specimens collected at baseline from the 283 participants who developed any disability and from 350 participants selected randomly (46.9%) from those who continued to be non-disabled.

FINDINGS

Participants in the highest IL-6 tertile were 1.76 (95% CI, 1.17-2.64) times more likely to develop at least mobility-disability and 1.62 (95% CI, 1.02-2.60) times more likely to develop mobility plus ADL-disability compared with to the lowest IL-6 tertile. The strength of this association was almost unchanged after adjusting for multiple confounders. The increased risk of mobility-disability over the full spectrum of IL-6 concentration was nonlinear, with the risk rising rapidly beyond plasma levels of 2.5 pg/mL.

INTERPRETATION

Higher circulating levels of IL-6 predict disability onset in older persons. This may be attributable to a direct effect of IL-6 on muscle atrophy and/or to the pathophysiologic role played by IL-6 in specific diseases.