COPD is a disease that affects 3.2% of the population attended by FPs; 90% of patients had one or more related diseases and 55% presented with three or more additional chronic diseases.
The morbidity seen in primary health care comes close to that reported in population-based studies. In a health care system such as Spain’s, citizens are not only required to register with a FP, but, in order to be eligible for hospital care, must first consult their FP.
In recently published population-based epidemiological study conducted in Spain, COPD prevalence was estimated at 10.2%. It is well known that COPD tends to be underdiagnosed by FPs [20
]. In our case a prevalence of 3.2% falls in the range found by Halbert [2
] in the studies that used respiratory symptoms based medical diagnosis as case definition. Comparing to the prevalence data from the previously referenced study [3
] which used GOLD criteria as case definition, family doctors might have been underdiagnosing 69% of the patient’s population suffering COPD. This is a high underdiagnosis ratio, comparable with that of previous studies, and it has scarcely changed in the last ten years.
At the date of our study, all health centres were supplied with spirometers but FPs are widely known to make little use of this particular diagnostic technique [23
]. Furthermore, underdiagnosis may also be influenced by FPs’ attitude to this disease: indeed, reluctance to label the patient is such that treatment may even be initiated before the formal diagnosis has been entered on the clinical record [26
Of the total, only 9% of patients presented with COPD alone, and the remainder tended to have a mean of four of the 25 chronic diseases studied. Being an aged population, the diseases or conditions involved are not only specific to older persons, but are also present at a frequency that is higher than expected, e.g., heart failure, arrhythmia, ischaemic heart disease, anxiety/depression, obesity, thyroid disease, asthma, osteoporosis, generalised artherosclerosis and chronic liver disease. Smoking-related inflammation is postulated as a possible cause of many of these diseases [7
While other studies have addressed the problem of comorbidity in patients with COPD, most have focused on a few isolated diseases. We, in contrast, studied the association between COPD and a further 25 chronic diseases. We found three studies which analysed the association between COPD and a long list of diseases in primary care patients but, as in the case of other comorbidity studies, comparison was hindered by methodological differences, in that two were based on data from ongoing records kept by volunteer physicians [27
] and the third used data drawn from EMRs [29
]. All three used the same case definition as ours, namely, COPD recorded by a FP. Results were controlled for age in only one study [27
]. Although the disease list used was not the same throughout, there was a substantial core group of diseases that was common to all the studies, including ours. As in our case, the other three studies also observed a high prevalence of cardiovascular diseases and osteoporosis.
COPD patients who also present with cardiovascular diseases register more episodes of COPD exacerbation, more hospital admissions, a notable increase in cost of medical care [30
] and higher cardiovascular disease mortality [31
]. In our case, 16% of patients presented with arrhythmia, 8.5% with ischaemic heart disease, and a further 8% with heart failure. This association has been reported in other studies [32
]. In a study focusing on family practices in Spain, de Miguel found that prevalence of heart disease among COPD patients was 19% [8
As reported by most studies [8
], cardiovascular risk factors, such as arterial hypertension, lipid metabolism disorders, diabetes and obesity, are among the most prevalent diseases in COPD patients. This, however, is due to the ageing of patients, since, once age had been controlled for, prevalence did not prove very different to what might have been expected (Table ). This finding indicates that, when studying the association between COPD and cardiovascular diseases, the confounding role of risk factors must be taken into account [33
We observed 89% more chronic liver diseases than expected in a general population of this age and sex. This association has been little described but a Japanese-based study, targeting family medicine offices attended by specialist physicians [35
], reported an elevated prevalence of chronic liver disease, chronic hepatitis C, hepatic steatosis and alcoholic hepatitis. Another study [36
] similarly observed this association between liver disease and COPD, after controlling for age, sex and smoking habit. In addition, COPD has been described as having a swifter progression in hepatitis C patients [37
]. Although, the aetiopathogenic mechanisms of this association are unclear, an interleukin-8 mediated chronic inflammatory process is suspected as being the cause [38
Furthermore, 7% of COPD patients have osteoporosis, with a frequency that is 10 times greater in women than in men, and an observed prevalence that is higher than expected for patients of their age and sex. Some studies report patients with COPD as having a threefold risk of presenting with osteoporosis [19
]. Since a number of studies have shown that inhaled corticoids have no effect on bone density, other factors, such as reduced mobility, smoking habit or adverse effects of other drugs, may be the cause of this.
Anxiety and depression are frequent among patients with COPD. In our study, 20% of patients presented with these problems, with a frequency that was twice as high in women as in men. In one review, prevalence varied widely between some studies and others, due in part to the measurement instrument used and type of patient studied. Among stable patients, prevalence of depression ranged from 10% to 42% and prevalence of anxiety from 10% to 19% [39
]. Our data are in line with those published. The causes for the increase in affective disorders in these patients are uncertain but, in addition to the reactive effect due to deterioration in the state of health, nicotine dependence may play an important role [40
Six per cent of our patients had COPD and asthma, with a frequency that was more than three times higher in women than in men. This prevalence is lower than that observed in population-based studies [41
], a finding probably explained by the same type of underdiagnosis as that which affects COPD. This overlapping of diseases in the same patient represents a diagnostic and therapeutic challenge for FPs [42
This study suffers from some limitations: firstly, there are those inherent in any retrospective design which uses EMRs as its data source. As a data source, medical records introduce biases stemming from under-registration and the poor quality of the data recorded [44
]. In an attempt to solve this problem, physicians were selected according to the quality of their records.
Another limitation derives from the case-definition criterion used, i.e., the need for patients’ clinical histories to show evidence of diagnosis of COPD, since FPs are well known for making little use of spirometry and for misclassifying COPD patients [45
]. However, in view of the fact that this was a chronic disease and of the longitudinal nature of primary care, it is likely that underdiagnosis involved the milder forms of COPD [22
] and that misclassification was due to COPD being diagnosed as asthma and vice-versa.