Using admixture analysis to examine birth-cohort effects on age at onset of bipolar disorder

Clinical correlates of late-onset versus early-onset bipolar disorder in a global sample of older adults

OBJECTIVES

Late-onset bipolar disorder (LOBD) represents a significant subgroup of bipolar disorder (BD). However, knowledge for this group is mostly extrapolated from small studies in subjects with early/mixed age of illness onset. In this global sample of older adults with BD (OABD: ≥50 years old) we aim to characterize the sociodemographic and clinical presentation of LOBD (≥40 years at BD onset) compared to early-onset BD (EOBD: <40 years at BD onset).

METHODS

The Global Aging and Geriatric Experiments in Bipolar Disorder consortium provided international data on 437 older age bipolar disorder participants. We compared LOBD versus EOBD on depression, mania, functionality, and physical comorbidities. Exploratory analyses were performed on participants with BD onset ≥50 years old.

RESULTS

LOBD (n = 105) did not differ from EOBD (n = 332) on depression, mania, global functioning, nor employment status (p > 0.05). Late-onset bipolar disorder was associated with higher endocrine comorbidities (odds ratio = 1.48, [95%CI = 1.0,12.1], p = 0.03). This difference did not remain significant when subjects with BD onset ≥50 years old were analyzed.

LIMITATIONS

This study is limited by the retrospective nature of the variable age of onset and the differences in evaluation methods across studies (partially overcame by harmonization processes).

CONCLUSION

The present analysis is in favor of the hypothesis that LOBD might represent a similar clinical phenotype as classic EOBD with respect to core BD symptomatology, functionality, and comorbid physical conditions. Large-scale global collaboration to improve our understanding of BD across the lifespan is needed.

Using density of antecedent events and trajectory path analysis to investigate family-correlated patterns of onset of bipolar I disorder: a comparison of cohorts from Europe and USA

BACKGROUND

Major contributors to the global burden of bipolar disorders (BD) are the early age at onset (AAO) and the co-occurrence of non-mood disorders before and after the onset of BD. Using data from two independent cohorts from Europe and the USA, we investigated whether the trajectories of BD-I onset and patterns of psychiatric comorbidities differed in (a) individuals with or without a family history (FH) of BD, or (b) probands and parents who both had BD-I.

METHODS

First, we estimated cumulative probabilities and AAO of comorbid mental disorders in familial and non-familial cases of BD-I (Europe, n = 573), and sex-matched proband-parent pairs of BD-I cases (USA, n = 194). Then we used time to onset analyses to compare overall AAO of BD-I and AAO according to onset polarity. Next, we examined associations between AAO and polarity of onset of BD-I according to individual experiences of comorbidities. This included analysis of the density of antecedent events (defined as the number of antecedent comorbidities per year of exposure to mental illness per individual) and time trend analysis of trajectory paths plotted for the subgroups included in each cohort (using R² goodness of fit analysis).

RESULTS

Earlier AAO of BD-I was found in FH versus non-FH cases (log rank test = 7.63; p = 0.006) and in probands versus parents with BD-I (log rank test = 15.31; p = 0.001). In the European cohort, AAO of BD-I was significantly associated with factors such as: FH of BD (hazard ratio [HR]: 0.60), earlier AAO of first non-mood disorder (HR: 0.93) and greater number of comorbidities (HR: 0.74). In the USA cohort, probands with BD-I had an earlier AAO for depressive and manic episodes and AAO was also associated with e.g., number of comorbidities (HR: 0.65) and year of birth (HR: 2.44). Trajectory path analysis indicated significant differences in density of antecedents between subgroups within each cohort. However, the time trend R² analysis was significantly different for the European cohort only.

CONCLUSIONS

Estimating density of antecedent events and comparing trajectory plots for different BD subgroups are informative adjuncts to established statistical approaches and may offer additional insights that enhance understanding of the evolution of BD-I.

Is being born in spring significantly associated with early-onset bipolar affective disorder? A case-control study

Few studies have investigated relationships between birth season and early-onset bipolar affective disorder (BAD) in young adults. In the current study, birth season was compared in patients with early-onset BAD and in sex-matched and age-matched controls. A total of 957 patients aged <25 years of age from three hospitals in the North China Plain region were enrolled in the study. Sex-matched and age-matched control group data were collected in universities and schools via questionnaires. The R*C chi-square test was used to assess distributional differences in season of birth both in the patient and control group. A binary logistic regression model adjusted for age and sex was used to evaluate associations between season of birth and BAD. Using spring as the reference season, BAD patients showed significantly lower odds ratios of being born in any other season. There were associations between birth season and early-onset BAD, and early-onset BAD patients were more likely to have been born in spring. These data have implications for future disease prevention strategies and future research.

Bipolar disorder: Trimodal age-at-onset distribution

OBJECTIVE

Bipolar disorder (BD) is a chronic mental health disorder with significant morbidity and mortality. Age at onset (AAO) may be a key variable in delineating more homogeneous subgroups of BD patients. However, no known research has systematically assessed how BD age-at-onset subgroups should be defined.

METHODS

We systematically searched the following databases: Cochrane Central Register of Controlled Trials, PsycINFO, MEDLINE, Embase, CINAHL, Scopus, Proquest Dissertations and Theses, Google Scholar and BIOSIS Previews. Original quantitative English language studies investigating AAO in BD were sought.

RESULTS

A total of 9454 unique publications were identified. Twenty-one of these were included in data analysis (n = 22981 BD participants). Fourteen of these studies (67%, n = 13626 participants) found a trimodal AAO distribution: early-onset (µ = 17.3, σ = 1.19, 45% of sample), mid-onset (µ = 26.0, σ = 1.72, 35%), and late-onset (µ = 41.9, σ = 6.16, 20%). Five studies (24%, n = 1422 participants) described a bimodal AAO distribution: early-onset (µ = 24.3, σ = 6.57, 66% of sample) and late-onset (µ = 46.3, σ = 14.15, 34%). Two studies investigated cohort effects on BD AAO and found that when the sample was not split by cohort, a trimodal AAO was the winning model, but when separated by cohort a bimodal distribution fit the data better.

CONCLUSIONS

We propose that the field conceptualises bipolar disorder age-at-onset subgroups as referring broadly to life stages. Demarcating BD AAO groups can inform treatment and provide a framework for future research to continue to investigate potential mechanisms of disease onset.

Psychiatric comorbidities in bipolar disorders: An examination of the prevalence and chronology of onset according to sex and bipolar subtype

OBJECTIVES

Bipolar Disorder (BD) is frequently comorbid with other psychiatric disorders. However, few studies systematically examine which disorders are more likely to occur pre- or post-BD onset. We examine the prevalence and Age At Onset (AAO) of psychiatric conditions in adults with BD.

METHODS

A structured clinical interview was used to assess lifetime history and AAO of alcohol and cannabis misuse, suicide attempts, anxiety and eating disorders in a French sample of euthymic patients with BD (n = 739). Regression analyses were used to test for statistically significant associations between rates and AAO of comorbidities in BD groups stratified by sex or subtype.

RESULTS

Prevalence of alcohol and cannabis misuse was associated with male sex and BD-I subtype; whilst most anxiety and eating disorders were associated with female sex. The AAO of most comorbid conditions preceded that of BD, except for panic disorder, agoraphobia and alcohol misuse. Few variations were observed in AAO of comorbidities according to groups.

LIMITATIONS

All assessments were retrospective, so estimates of prevalence rates and especially exact AAO of some comorbidities are at risk of recall bias.

CONCLUSIONS

Sex and BD subtype are associated with different rates of comorbid disorders. However, there were minimal between group differences in median AAO of comorbidities. By describing the chronological sequence of comorbidities in BD we were able to demonstrate that a minority of comorbidities typically occurred post-onset of BD. This is noteworthy as these disorders might be amenable to interventions aimed at early secondary prevention.

Secular trends in the age at onset of bipolar I disorder - Support for birth cohort effects from interational, multi-centre clinical observational studies

OBJECTIVE

To examine any association of birth decade, sex and exposure to alcohol and/or substance use disorders (ASUD) with age at onset (AAO) of bipolar I disorder (BD-I).

METHODS

Using data from a representative clinical sample of 3896 BD-I cases recruited from 14 European countries, we examined AAO distributions in individuals born in consecutive birth decades. Cumulative probabilities with Mantel-Cox log-rank tests, pairwise comparisons and Odds Ratios (OR) with 95% confidence intervals (95% CI) were employed to analyze AAO according to birth decade, sex, and presence or absence of an ASUD.

RESULTS

In the total sample, median AAO of BD-I decreased from about 41 years for those born in the 1930s to about 26 years for those born in the 1960s. In a sub-sample of 1247 individuals (selected to minimize confounding), AAO significantly decreased for males and females born in each consecutive decade between 1930 and 50 (OR: 0.65; 95% CI: 0.51, 0.81), and for cases with an ASUD as compared to without (OR: 0.77, 95% CI: 0.69, 0.87). The best fitting regression model identified an independent effect for each birth decade and an interaction between ASUD status and sex, with a consistently earlier AAO in males with an ASUD (OR: 0.79: 95% CI: 0.70, 0.91).

CONCLUSIONS

In BD-I cases diagnosed according to internationally recognized criteria and recruited to pan-European clinical observational studies, the AAO distributions are compatible with a birth cohort effect. A potentially modifiable risk factor, namely ASUD status, was associated with the observed reduction in AAO, especially in males.

Clinical correlates of age at onset distribution in bipolar disorder: a comparison between diagnostic subgroups

Background

Admixture analysis of age at onset (AAO) has helped delineating the clinical profile of early onset (EO) bipolar disorder (BD). However, there is scarce evidence comparing the distributional properties of AAO as well as the clinical features of EO BD type 1 (BD1) with EO BD type 2 (BD2). To this end, we studied 515 BD patients (224 BD1, 279 BD2, and 12 BD not otherwise specified [NOS]) diagnosed according to DSM-IV-TR criteria.

Methods

AAO was defined as the first reliably diagnosed hypo/manic or depressive episode according to diagnostic criteria. We used normal distribution mixture analysis to identify subgroups of patients according to AAO. Models were chosen according to the Schwarz’s Bayesian information criteria (BIC). Clinical correlates of EO were analysed using univariate tests and multivariate logistic regression models.

Results

A two normal components model best fitted the observed distribution of AAO in BD1 (BIC = −1599.3), BD2 (BIC = −2158.4), and in the whole sample (BIC = −3854.9). A higher number of EO BD2 patients had a depression-(hypo)mania-free interval (DMI) course, while a higher rate of (hypo)mania-depression-free interval (MDI) course was found in EO BD1. EO BD2 had also a higher rate of comorbidity with alcohol dependence compared to EO BD1. The latter finding was confirmed by multivariate logistic regression analysis.

Conclusions

In conclusion, both BD1 and BD2 had bimodal AAO distributions, but EO subgroups had a diagnostic-specific clinical delineation.

Understanding Early Age of Onset: a Review of the Last 5 Years

The age at onset of bipolar disorder ranging from childhood to adolescent to adult has significant implications for frequency, severity and duration of mood episodes, comorbid psychopathology, heritability, response to treatment, and opportunity for early intervention. There is increasing evidence that recognition of prodromal symptoms in at-risk populations and mood type at onset are important variables in understanding the course of this illness in youth. Very early childhood onset of symptoms including anxiety/depression, mood lability, and subthreshold manic symptoms, along with family history of a parent with early onset bipolar disorder, appears to predict the highest risk of early onset disorder with the most severe course.