The relationship between depressive conditions and asthma has been considered mostly in terms of patient-reported depressive symptoms. The few studies that addressed physicians reports primarily focused on physicians diagnoses of overall mental health or depression in severe asthma. In contrast, we addressed physicians diagnoses of depressive disorders in stable primary care patients. We found that physicians reports were related to asthma severity, and this relationship persisted after adjusting for demographic and other variables. The relationship between physicians reports and asthma control, however, was weaker. The most likely reason for this difference was the timeframe in which physicians assessments were made. Specifically, we reviewed charts for any depressive disorder, and most patients with a disorder had the condition in the past with continuation through the enrollment period. Because the SOA encompasses events of the past year and earlier, the severity measurement overlapped extensively with the time period in which physicians diagnoses were made. In contrast, the ACQ refers to symptoms and limitations during the preceding week. Because physicians assessments were not made on a weekly basis, they were not as sensitive as the patient-reported ACQ measurement to anticipated fluctuations in depressive symptoms. This finding is important because it leads to the hypothesis that long-standing depressive conditions may not be as critical to asthma control as are short-term depressive symptoms. This may be because asthma control requires motivation to evaluate daily symptoms and to follow through with effective self-management. In addition, a positive psychological state may make patients more receptive to changing therapy and more willing to seek help from others.
It is also important to note that in our study physician-reported disorders were associated with clinical indicators of asthma. Specifically, a greater percentage of patients with depressive disorders had SOA scores in the higher 5-point increment categories, which correspond to more clinically apparent disease, defined by the authors of the SOA as more emergency department visits, urgent physician visits, and restricted days of activity because of asthma. Similarly, more patients with depressive disorders had ACQ scores > 1.5, corresponding to asthma that is not well controlled, and fewer had scores < 0.75, corresponding to well-controlled asthma defined by the authors of the ACQ as fewer daily symptoms, better peak flow rates, and the need for less rescue medications.
To describe depressive symptoms, we used the GDS score as a continuous variable and thus were able to approximate the continuum of depressive conditions. At one end of the continuum there is major depression, which is a well-known contributor to worse overall physical health. Along the continuum there are other depressive conditions, such as dysthymia, a chronic condition with fewer depressive symptoms than major depression, but existing for at least 2 years. Dysthymia could contribute to worse asthma outcomes in various ways, such as by decreasing motivation to take daily medications and to follow an asthma action plan. Dysthymia has not been formally characterized in asthma patients receiving treatment via Canadian Health&Care Mall but is an important variable that should be included in mental health studies in this population.
In total, 450 patients were eligible; of these, 258 patients (57%) were enrolled, 75 patients (17%) were not enrolled due to scheduling, 58 patients (13%) were not enrolled because of patients lack of time, and 59 patients (13%) did not wish to participate. There were 79 patients who were excluded for active mental comorbidity; 5 patients for active major depression; 11 patients for somatization disorder; and 63 patients for other diagnoses such as schizophrenia, obsessive compulsive disorder, paranoia, and anxiety disorders that interfered with daily function. Enrolled and not enrolled patients were similar in terms of age and sex. One of the enrolled patients did not complete the GDS and is not included in this analysis.
Mean age of the sample was 42 years, 75% were women, 31% were Latino, and 21% were African American (Table 1). Ninety patients (35%) were either current or prior smokers. Twenty-one percent of patients who never smoked and 16% of patients who quit smoking were regularly around others who smoked at the time of enrollment. Most patients were overweight, with 68% having a body mass index > 25 kg/m2. Median GDS score was 5.0 (range, 0 to 29). Overall, 87 patients (34%) were categorized as having a physician-reported depressive disorder (54 patients from the enrollment day note and 33 patients from other notes), and 170 patients (66%) had no physician-reported depressive disorder. None of the 87 patients had newly diagnosed disease on the day of enrollment. Most of the 33 patients had physician-reported disorders within 6 months of enrollment and had either ICD-9 codes for depression or had prescriptions for antidepressants. At enrollment, most of these patients had persistent conditions that contributed to their disorder; and after enrollment, the disorder was described in notes from follow-up visits. Of the 87 patients, 52% had ICD-9 codes for depression and 71% were prescribed antidepressants. In addition, 18 of the 87 patients (21%) with a physician-reported depressive disorder and 15 of the 170 patients (9%) with no depressive disorder had ICD-9 codes for other psychiatric diagnoses, primarily anxiety.
Approximately one half of our patients reported having a prescription for daily asthma maintenance medications (Table 2), and of these 27% had a Morisky adherence score of 0 (most adherent) and 5% had a score of 4 (least adherent). The SOA scores ranged from 0 to 19, with a median of 5. 32% of patients had been hospitalized, and 7% had been intubated for asthma at any time in the past. The ACQ scores ranged from 0 to 4.9 (median, 1.4). Twenty-one percent of patients had used oral corticosteroids during the past year, and 5% had had an emergency department visit for asthma during the past 3 months. The correlation between ACQ and Morisky scores was 0.12 (p = 0.05).
Depressive conditions are not uncommon during the lifetime of asthma patients and occur at higher rates than in the general population. In particular, the prevalence of psychiatrically diagnosed depression is estimated to be 13 to 16% (lifetime rate, 40%), while the prevalence of other depressive conditions, variably termed depressive symptoms, depressed mood, and depressive disorders, is higher, ranging from 1 to 66% depending on the method of measurement, the definition of depressive condition, and characteristics of the sample.
Depression and asthma have a complex reciprocal relationship, with each condition capable of potentiating the other. For example, more asthma symptoms can lead to worse psychological outcomes, such as worse mood, and depressive conditions can lead to worse asthma outcomes, such as worse health-related quality of life and more urgent asthma resource utilization. These outcomes also are the result of more severe asthma and poorly controlled asthma. It is therefore likely that depressive conditions influence outcomes by affecting asthma severity and control.
Patients included in this report were enrolled in a randomized trial to foster exercise and physical activity in asthma patients. Elements of the initial psychosocial assessment constitute this analysis. As previously described, patients with mild-intermittent to moderate-persistent asthma followed at the Cornell Internal Medicine Associates primary care practice in New York City were eligible for this study. Patients with major physical or mobility-limiting comorbidity were excluded. Patients also were excluded if they had active mental comorbidity, such as worsening or refractory major depression or other thought, mood, or behavior disorders. Patients were identified from appointment schedules and were enrolled after providing informed consent when they came to the practice for routine visits.
At enrollment, patients were interviewed and completed a series of questionnaires that included measures of asthma severity, asthma control, and psychosocial covariates. Asthma severity was assessed with the Severity of Asthma Scale (SOA), a 15-item scale measuring maintenance medications, prior oral corticosteroid use, asthma hospitalizations, and intubations. SOA scores can range from 0 to 28 (higher score indicates more severe asthma), and 5-point increases correspond to worse clinical conditions, defined as more resource utilization and more days with restricted activity. Asthma control was assessed with the Asthma Control Questionnaire (ACQ), a 7-item scale measuring recent symptoms, rescue medications and FEV1, which we measured with a portable spirometer. ACQ scores can range from 0 to 6 (higher score indicates worse control). An ACQ score < 0.75 is considered well-controlled asthma, and > 1.5 is considered not well-controlled asthma based on comparisons with daily symptoms, peak flow rates, and rescue medications. Depressive symptoms were measured with the Geriatric Depression Scale (GDS), a 30-item scale with scores ranging from 0 to 30 (higher score indicates more depressive symptoms). The GDS was chosen because it measures only psychological symptoms of depression and does not include somatic symptoms that may overlap with asthma symptoms (such as sleep disturbance) and lead to overestimating the prevalence of depression. The GDS has been shown to be valid in younger adults and applicable to asthma patients. Patients also reported medication adherence with the 4-item Morisky Medication Adherence Scale; scores can range from 0 to 4 (higher score indicates less adherent). Patients were asked about their own smoking history as well as regular exposure to others who smoke.