Several key risk factors are likely to accelerate the progression from asthma to a diagnosis of chronic obstructive pulmonary disease (COPD), according to the results of a large, population-based 18-year Canadian cohort study recently published in the journal COPD.

Recognizing that risk factors accelerating time-to-COPD diagnosis have not been clearly identified, the investigators in the current study sought to estimate risk factors associated with the incidence of COPD diagnosis among patients with asthma. They used 4 health administrative claim databases obtained from the Population Data in the British Columbia (PopData BC) province of Canada to identify all patients with asthma without a prior diagnosis of COPD between January 1, 1998, and December 31, 1999. All participants were evaluated for time-to-incidence of COPD diagnosis from January 1, 2000, through December 31, 2018. The primary study outcome measure was the time to first diagnosis of COPD during the 18-year follow-up period.

Estimates of several risk factors for predicting the incidence of COPD in patients with asthma during the study follow-up included such sociodemographic factors as year of the index (January 1, 1998, to December 31, 1999), sex, age, presence of obesity (BMI >30 kg/m2), and lifestyle variables (tobacco use/nicotine dependence). Additional risk factors evaluated included asthma medication adherence, which was assessed by 2 proxy variables on a scale of 0 to 1, defined as the proportion of days covered and the medication possession ratio, as well as the Charlson comorbidity index (CCI), which measured the burden of comorbid conditions among the patient identified with asthma after excluding asthma from the score.


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A total of 68,211 patients with physician-diagnosed asthma at baseline were identified from the 4 linked PopData BC databases between January 1, 1998, and December 31, 1999. The incidence of COPD diagnosis was established in the 18-year follow-up period from January 2, 2000, through December 31, 2018. After 1,036,811 years of person-time follow-up, 15% (10,170 of 68,211) of patients were diagnosed with COPD. Based on disease severity, the incidence of COPD diagnosed among patients with mild asthma was 0.86 per 1000 person-years (n=886), 2.82 per 1000 person-years among patients with moderate asthma (n=2924), and 6.13 per 1000 person-years among patients with severe asthma (n=6360).

The mean patient age was 48.2 years; 40.09% of the patients were male. Regarding the burden of comorbidities linked to asthma at baseline, 97.88% of the patients who constituted the majority had no comorbid condition (CCI score of 0), whereas 1.80% had a CCI score of 1 and 0.32% had a CCI score of 2 or more. At baseline, 2 asthma-related comorbid conditions were identified — that is, sinusitis in 0.16% of patients and upper respiratory tract infections in 0.42% of patients.

Per multivariate analysis, risk factors that accelerated the time-to-COPD diagnosis included the following: (1) male sex (adjusted failure time ratio [aFTR], 0.62; 95% CI, 0.56- 0.68; P <.0001), (2) older adults (ie, age >40 years; aFTR, 0.03; 95% CI, 0.02-0.04; P <.0001), (3) history of tobacco smoking (aFTR, 0.29; 95% CI, 0.13-0.6; P =.004), (4) asthma exacerbation (aFTR, 0.81; 95% CI, 0.70-0.94; P =.007), (5) frequent emergency department admissions (aFTR, 0.21; 95% CI, 017-0.25; P =.000), (6) longer length of hospital stay (aFTR, 0.07; 95% CI, 0.06-0.09; P <.0001), (7) increased burden of comorbidities (aFTR, 0.28; 95% CI, 0.22-0.34; P <.0001 [per CCI score]), (8) male patients with obesity (aFTR, 0.38; 95% CI, 0.15-0.99; P value not available), (9) short-acting  beta-2 agonist overuse (aFTR, 0.61; 95% CI, 0.44-0.84; P =.003), (10) moderate asthma (aFTR, 0.23; 95% CI, 0.21-0.26; P =.000), and (11) severe asthma (aFTR, 0.10; 95% CI, 0.08-0.12; P =.000).

Following adjustment, a medication adherence of at least 0.80 was associated with an 83% significantly delayed time-to-COPD diagnosis (aFTR, 1.83; 95% CI, 1.54-2.17 for proportion of days covered; P <.0001). Asthma severity, however, significantly modifies the effect of medication adherence, independent of history of tobacco smoking.

The investigators concluded that the targeted intervention intended to mitigate early diagnosis of COPD may prioritize the enhancement of medication adherence among patients with asthma, in an effort to prevent frequent exacerbations during follow-up. Patient education and counseling should be intensified to enhance awareness of the importance of adhering to prescribed medications over time, along with minimizing such unhealthy lifestyles as cigarette smoking and sedentary lifestyles, which are linked to obesity, especially among male patients.

Reference 

Asamoah-Boaheng M, Farrell J, Osei Bonsu K, Midodzi WK. Examining risk factors accelerating time-to-chronic obstructive pulmonary disease (COPD) diagnosis among asthma patients. COPD. Published online January 10, 2022. doi:10.1080/15412555.2021.2024159