RESULTS
The flowchart is presented in Fig. 1. We identified 82421 patients with
constipation and 82421 matched controls between 1999 and 2013 from the
LHID. Demographic characteristics of this study participants are shown
in Table 1. The constipated patients and non-constipation cohort were
similar in age and gender distribution. After propensity score matching,
there were no statistically significant differences between the
constipation and non-constipation groups.
As shown in Table 2, the incidence of asthma was 10.8 per 1,000
person-years in the constipation group, which was higher than the rate
of 5.6 per 1,000 person-years observed in the non-constipation group.
After adjustment, patients with constipation had a significantly higher
risk of asthma than those without constipation (aHR:1.91, 95% C.I.
1.84-1.99, p<0.001). Compared with women, men had a
significantly higher risk of asthma (aHR:1.17; 95% CI, 1.12-1.22;
p<0.001). In term of comorbidities, we observed that people
with hypertension, COPD, or autoimmune disease had a relatively higher
risk of asthma. (hypertension:1.22, 95% C.I. 1.15-1.29,
p<0.001; COPD:3.21, 95% C.I. 2.94-3.50, p<0.001;
autoimmune disease:1.42, 95% C.I. 1.17-1.73, p<0.001). By
contrast, patients using corticosteroids or antihistamines during the
study for period at least 30 days had a lower risk of asthma.
(corticosteroids: 0.80, 95% C.I. 0.76-0.84, p<0.001;
antihistamines: 0.61, 95% C.I. 0.59-0.64, p<0.001)
Table 3 showed that subgroup analyses were performed to assess the
association between constipation and asthma based on demographic
characteristics. Patients in the constipation group aged 20-39 years,
had a 2.04-fold greater risk of asthma compared with the same age group
in the non-constipation group (aHR; 95% CI,1.84-2.26, P <
0.001). Patients aged <20, 40-64, and ≥65 years in the
constipation group had a 1.85, 1.70, and 2.02-fold greater risk of
asthma.(aHR; 95% CI, 1.69-2.01, 1.57-1.83 and 1.89-2.16; P <
0.001), respectively. Among females, compared with those without
constipation, there was a 1.86-fold higher risk of asthma in patients
with constipation (aHR; 95% CI, 1.77-1.96; P < 0.001). Among
males, there was 1.92-fold higher risk of asthma in patients with
constipation (aHR; 95% CI, 1.80-2.04; P < 0.001).
Furthermore, constipated patients had a higher likelihood of asthma,
regardless of comorbidities and medications.
In addition, Table 4 presents that analysis for risk of asthma in
constipated patients with laxatives prescription. Compared to
participants without constipation, the adjusted hazard ratio was 1.76
(95% CI, 1.69-1.85; P < 0.001), 2.15(95% CI, 2.03-2.27; P
< 0.001), and 2.29(95% CI, 2.10-2.49; P < 0.001)
for < 3 times, 3-12 times, and ≥12 times of laxatives
prescription within one year, respectively. There appeared to be a
dose-effect relationship between constipation severity and risk of
asthma.The Kaplan–Meier curves are shown in Fig. 2. The cumulative
incidence of asthma was significantly higher in constipated patients
than in non-constipated patients, and the log-rank test for the
comparison of cumulative incidence curves resulted in a P-value of
<0.001