Presence of depression and anxiety before and after coronary artery bypass graft surgery and their relationship to age

The prevalence of depression in patients with diagnosed coronary heart disease (CHD) is quoted between 20 and 45% [1, 2]. Elevated anxiety scores have been reported for 20 to 55% [3, 4]. The same prevalence ratios have been found for patients undergoing CABG surgery [5].

Depression is regarded as an independent risk factor for arteriosclerotic deposits in coronary arteries [6]. The pathophysiological processes to explain this relationship are hypercortisolaemia related to e.g. insulin resistance, sympathetic vagal dysbalance related to e.g. disturbed regulation of blood pressure, and an unfavourable lifestyle like cigarette smoking [7]. Depression does not only account for a raise in first time CHD manifestation, but it is also related to the success of secondary and tertiary prevention:

1. presurgical [8] as well as postsurgical [9] depression increases physical and psychosocial morbidity six month [8] and five years [9] after CABG-surgery,

2. preoperative depression is a significant predictor of mortality in the period 30 days after CABG-surgery [10],

3. depressed patients have a lower functional status [11] and less health status benefits six month after CABG surgery [12],

4. post myocardial infarction (MI) depression reduces the probability of secondary CHD prevention four month after MI [13].

Depressed patients with MI are reported to increase economical burdens [14]. Based on a Canadian sample, patients being depressed during the first year following MI produce approximately 41% higher health-care costs than non-depressed patients [14].

In contrast to depression, anxiety is not considered an independent risk factor for MI. Depression is associated with higher postoperative mortality and morbidity. The same relationship was found for acute preoperative anxiety but not for trait anxiety [15]. It is reported, however, that the risk of sudden cardiac death is elevated by anxiety disorders. Pathophysiologically ventricular arrhythmias are considered to explain this phenomenon [16].

Patients who undergo CABG surgery nowadays are older than a decade before. In Germany, in the year 2004 42.8% of all procedures using cardiopulmonary bypass were performed in patients older than 70 years, whereas in 1994 the percentage was 24.9% [17]. Increased age is considered to be a high risk factor for perioperative mortality. Age is one of the few factors which is included in all of the formulas to calculate mortality risk [18].

Furthermore, it is known that depression affects the life of elderly people more than any physical disorder [19]. No consistent pattern across studies investigating age differences in the occurrence of anxiety and depression is available in the current literature [20]. To our knowledge, the prevalence of clinically relevant anxiety and depression in patients undergoing CABG-surgery in relation to age has not been investigated yet.

The objective of the present study was to evaluate the proportion of clinically relevant anxiety and depression and the number of symptoms for both conditions in CHD patients two days before and ten days after CABG surgery in relation to age.

The percentage of patients who filled in the HADS was different between the age groups (see Table 1). Before surgery there were no significant differences (Fisher's exact: p = 0.12). Ten days after CABG surgery, however, we found highly significant differences (Chi-square = 16.7, df = 3; p < 0.001). The older the age group was the less patients filled in the HADS. Statistically significant differences resulted only by comparing age group "36–60 years" with age group "73–78 years" (Chi-square = 12.9; df = 1; p < 0.001) and age group "36–60 years" with age group "67–72 years" (Chi-square = 5.1; df = 1; p = 0.02).

Data analyses with the categorical classification indicate for anxiety that 34.0% of the patients before, 24.7% after CABG surgery, and 16.5% at both time points were highly anxious. 25.8% of the patients were depressed two days before CABG surgery, 17.5% ten days after, and 9.3% at both questionnings. For both, anxiety and depression, the changes in these ratios are not significant (McNemar test). However, by testing the accompanied continuous HADS scores a statistically significant decline could be found for anxiety (before surgery: m = 6.78; SD = 3.86, after surgery: m = 5.38; SD = 3.75, T(96) = 3.82; p < 0.001) as well as for depression (before surgery: m = 5.65; SD = 3.71, after surgery: m = 4.51; SD = 4.08, T(96) = 3.35; p = 0.001).

The nonparametric McNemar test supports the post-hoc findings, because the amount of high scorers in anxiety is diminished only in the youngest patient group (McNemar = 4.16; df = 1; p = 0.04).

Before CABG surgery, age did not seem to have any influence on the rate of completion of the HADS. After surgery, however, completion rate decreased significantly with age. This cannot be explained by higher medical complication rates that prevented the patients from filling in the questionnaire. Potential explanations could be physical impairment, a general weakness, and/or the unfamiliar cognitive demand of the test putting too much strain on older patients. In addition, the questionnaire explicitly asks for mental concerns. According to our experience, older people are prone to react to questions like these with avoidance tendencies which could mask psychiatric comorbidity. One of our first assumptions was that patients with elevated anxiety or depression scores two days before CABG surgery would not fill in the HADS for a second time. However, this could not be supported by our data because the number of missing data ten days after CABG was independent of the status of anxiety and depression, respectively (i.e. high-scorers vs. normal scorers). The quantity of missing data is the main limitation of our investigation. However, the results are congruent with our clinical impressions.

The increased anxiety and depression rates in our study, compared to the general population, are in accordance with those described in the literature [1, 5, 8]. The decline in anxiety and depression scores from pre to post CABG surgery points to the fact that the patients are under considerable psychic strain before CABG surgery.

Furthermore, we could demonstrate negative correlations between age and changes in depression and anxiety scores. A closer inspection of these negative correlations and the ANOVA results revealed that the younger the patients are the larger is the decrease from pre- to post-surgery scores. There are some possible reasons for the specific age related pattern of anxiety and depression. Information about the surgery, which is routinely performed prior to surgery, may induce thoughts of one's own potential death, since death is mentioned as a possible complication of CABG surgery. These thoughts could have been present in the younger as well as in the older patients. It seems that older patients consider anticipated relief more than the strain imposed by angina pectoris. Younger patients, however, suffer from less physical limitations caused by CHD than the older ones. Therefore it is possible that before CABG surgery the younger patients are more affected by a potential deadly outcome than by the removal of physical CHD symptoms. Another possible explanation is that during their lives older patients were more frequently confronted with thoughts of their own death. As a consequence of knowing the stimulus "own death" patients may habituate resulting in less anxiety. In addition, younger patients may estimate their mortality risk and how long they will live. So, they might calculate a much greater loss than older patients, and stronger anxiety is elicited with the assumed number of years ahead of them. While discussing our results with a 75 year old male patient he mentioned another possible reason. Elder patients mostly have CHD for several years and may have become trained in getting into the hospital. Therefore, they are confronted with fewer new stimuli as compared to most of the younger patients.

Remarkably, the ratio of patients with elevated depression values at both time points is only 9.3%. Such a low ratio has not been reported before and may depend on the longitudinal design of our study, while other studies evaluate depression only at a single time point, e.g. before or shortly after CABG surgery.

Based on the results of our study one may conclude: Many patients have noticeable mental distress before CABG surgery which has to be recognized and treated. The younger the patients are the higher is the decline of symptoms. The older the patient are the less change of symptoms is observed. According to these findings anxiety specific symptoms, e.g. tachycardia, should be kept in mind especially for younger patients before CABG surgery. In short term care and before surgery, treatment should predominantly focus on anxiety. Anxiolytic drugs should be prescribed as soon as possible, and potential threats should be avoided. In this regard, a trustful physician-patient-relationship is of importance. On the other hand, to sustain a good long-term outcome after CABG surgery treatment of depression surely is more important than treatment of anxiety. With some exceptions [25], for many patients the best depression therapy is a combination of antidepressants and psychotherapy. The basics of sufficient treatment, however, are reliable and valid diagnostic investigations.