Hemoglobin A1c-levels and subsequent risk of depression in individuals with and without diabetes

BACKGROUND

It has been suggested that long-term glycemic load as reflected in plasma levels of Glycosylated Hemoglobin, Type A1C (HbA1c) is associated with higher risk of depression, however results have been conflicting. We examined the potential association between HbA1c and risk of depression in a large population-based cohort without baseline diabetes (the Glostrup cohort) defined by either self-reported diabetes, registry diagnosis of diabetes or use of antidiabetic medication at baseline and in a national diabetes cohort (the Danish Adult Diabetes Database).

METHODS

A total of 16,124 middle-aged individuals from the Glostrup cohort and 93,544 patients registered in the Danish Adult Diabetes Database were followed from the first registered HbA1c measurement (1999-2014) for subsequent diagnosis of depression or use of antidepressant medication in nation-wide Danish registers. The association was analyzed using a Cox proportional hazards regression model with HbA1c on both a continuous scale using restricted cubic splines and categorized based on the groups found in the spline model. We adjusted for relevant sociodemographic and clinical variables including previous depression and tested for interaction of both gender, insulin use and diabetes type.

RESULTS

During follow-up, 2694 (17%) in the Glostrup cohort and 29,234 (31%) in the diabetes cohort developed depression. In the Glostrup cohort, we found an indication of a positive linear association between HbA1c and depression in women, while no clear association was found in men. In patients with diabetes, we found a U-shaped association between HbA1c and depression in both men and women with the lowest risk estimates for HbA1c levels of 58 mmol/mol (7.5%) in men and of 60 mmol/mol (7.6%) in women. When HbA1c was categorized, men with the highest HbA1c-levels had significantly elevated risk of depression (HR_HbA1c>9.4 1.16 (95%CI 1.10-1.23)) after multifactorial adjustment compared to the reference group with HbA1c of 42.1-56.2 mmol/mol (6.0-7.3%). Women in the lowest and highest category of HbA1c had significantly higher risk of depression HR_HbA1c<6.0 1.15 (95% CI 1.09-1.22) and HR_HbA1c>9.3 1.10 (95% CI 1.04-1.16), respectively, compared to the reference group with HbA1c 42.1-55.0 mmol/mol (7.2-9.3%). There was a significant interaction with gender, but no interaction for insulin use or diabetes type.

CONCLUSIONS

In a population without baseline diabetes, higher HbA1c levels seemed associated with higher depression risk in women, whereas a U-shaped association was found in patients with known diabetes.

Intrauterine testosterone exposure and depression risk in opposite-sex and same-sex twins, a Danish register study

BACKGROUND

Males have a lower prevalence of depression than females and testosterone may be a contributing factor. A comparison of opposite-sex and same-sex twins can be used indirectly to establish the role of prenatal testosterone exposure and the risk of depression. We therefore aimed to explore differences in depression risk using opposite-sex and same-sex twins.

METHODS

We included 126 087 opposite-sex and same-sex twins from the Danish Twin Registry followed in nationwide Danish registers. We compared sex-specific incidences of depression diagnosis and prescriptions of antidepressants between opposite-sex and same-sex twins using Cox proportional hazard regression.

RESULTS

During follow-up, 2664 (2.1%) twins were diagnosed with depression and 19 514 (15.5%) twins had purchased at least one prescription of antidepressants. First, in male twins, we found that the opposite-sex male twins had the same risk of depression compared to the same-sex male twins {hazard ratio (HR) = 1.01 [95% confidence interval (CI) 0.88-1.17)]}. Revealing the risk of use of antidepressants, the opposite-sex male twins had a slightly higher risk of 4% (HR = 1.04 (95% CI 1.00-1.11)) compared with the same-sex male twins. Second, in the female opposite-sex twins, we revealed a slightly higher, however, not statistically significant risk of depression (HR = 1.08 (95% CI 0.97-1.29)) or purchase of antidepressants (HR = 1.01 (95% CI 0.96-1.05)) when compared to the same-sex female twins.

CONCLUSIONS

We found limited support for the hypothesis that prenatal exposure to testosterone was associated with the risk of depression later in life.

Familial risk and heritability of depression by age at first diagnosis in Danish twins

OBJECTIVE

Familial and genetic factors seem to contribute to the development of depression but whether this varies with age at diagnosis remains unclear. We examined the influence of familial factors on the risk of depression by age at first diagnosis.

METHODS

We included 23 498 monozygotic and 39 540 same-sex dizygotic twins from the population-based Danish Twin Registry, followed from 1977 through 2011 in nationwide registers. We used time-to-event analyses accounting for censoring and competing risk of death to estimate cumulative incidence, casewise concordance, relative recurrence risk, and heritability of first depression by age using monozygotic and same-sex dizygotic twin pairs.

RESULTS

During follow-up, a total of 1545 twins were diagnosed with depression. For twins at age 35 or younger at first depression, heritability was estimated to be 24.8% (95% confidence interval [CI], 4.6-43.1%), whereas at age 90 it was 14.7% (95% CI, 3.1-26.3%). The relative recurrence risk was higher at younger ages: At age 35, the risk was 27.7-fold (95% CI, 20.0-35.5) and 6.9-fold (95% CI, 3.9-9.8) higher than the population risk for monozygotic and same-sex dizygotic twins, respectively, while the corresponding numbers were 3.0 (95% CI, 2.3-3.6) and 1.8 (95% CI, 1.3-2.2) at age 90. Heritability seemed similar for male and female twins.

CONCLUSION

Familial risk of depression, caused either by genes or shared environment, seemed to slightly decrease with age at diagnosis and an elevated concordance risk for monozygotic over same-sex dizygotic pairs suggested a genetic contribution to the development of depression.

Incidence of suicidal behaviour and violent crime following antidepressant medication: a Danish cohort study

OBJECTIVE

To examine the incidence of suicidal and violent behaviour following initiation of antidepressant medication.

METHOD

Cohorts of 997 911 conscripts and 95 794 patients with a first-time affective disorder were followed for purchase of antidepressant medication, suicide, suicide attempts and conviction for violent crime in Danish registries between 1997 through 2015. Incidence of outcomes was estimated for the first 28 days, 28-365 days or later after initiation of antidepressants or study entry.

RESULTS

Of 16.5% of conscripts and 73.7% of patients with affective disorders initiated antidepressant medication. Incidence of suicide was 3-4 times higher during the first 28 days after initiation compared to the rates in the following year in both cohorts. A similar trend was seen among the untreated patients with affective disorders, whereas suicide incidence was stable at a low level among conscripts not treated with antidepressants. Incidence of attempted suicide was highest during the 28 days before and after initiation of antidepressants, while rates of violent crime were similar before and after initiation. These trends in incidence were independent of class of antidepressant.

CONCLUSION

Higher rates of suicidal behaviour in the weeks following initiation of antidepressant medication probably reflect disease severity and a delay in mood response.

The association between depressive mood and ischemic heart disease: a twin study

OBJECTIVE

Individuals with mood disorders have increased risk of cardiovascular disease. The aims of this study were to evaluate if the risk of cardiovascular disease in individuals with mood disorder could be explained by shared genetic and early environmental factors.

METHODS

We included 6714 Danish middle and old aged twins from two large population-based studies. Cox proportional hazards regression was used to perform individual-level and intra-pair analyses of the association between self-reported depression symptomatology scores and register-based diagnoses of ischemic heart disease.

RESULTS

Higher depression symptomatology scores (both total, affective, and somatic) were associated with higher incidence of ischemic heart disease after multivariable adjustment in individual-level analyses. In intra-pair analyses, this association was similar but with slightly larger confidence intervals. There was no interaction with gender and no major differences between mono- or dizygotic twins. Within twin pairs, the twin scoring highest on depressive symptoms developed ischemic heart disease more often or earlier than the lower scoring twin. A sensitivity analysis including a 2-year time lag of depression symptomatology to limit the risk of reverse causality showed similar results.

CONCLUSION

Genetic factors and early life environment do not seem to explain the association between depressive mood and ischemic heart disease.

Association between the antioxidant uric acid and depression and antidepressant medication use in 96 989 individuals

OBJECTIVE

In the last decade, several studies have suggested that depression is accompanied by increased oxidative stress and decreased antioxidant defenses. We tested the hypothesis that high levels of the antioxidant uric acid are associated with lower risk of hospitalization with depression and use of prescription antidepressant medication.

METHOD

We examined plasma levels of the antioxidant uric acid in 96 989 individuals from two independent cohort studies. Logistic regression and Cox proportional hazards regression models were multivariable adjusted for age, gender, alcohol, smoking, income, body mass index, C-reactive protein, hemoglobin, triglycerides, cardiovascular disease, diabetes, and intake of meat and vegetables. Results were performed separately in each study and combined in a meta-analysis.

RESULTS

In both studies, high uric acid was associated with lower risk of hospitalization as in-patient or out-patient with depression and antidepressant medication use. A doubling in uric acid was associated with an effect estimate of 0.57 (95% CI 0.49-0.65) and 0.77 (0.73-0.81) for hospitalization with depression and antidepressant medication use. The association was consistent across strata of all covariates. Results were attenuated in Cox regression analyses with less statistical power.

CONCLUSION

High plasma levels of uric acid were associated with low risk of depression hospitalization and antidepressant medication use.