Statistics sheet — asthma
Last curated: 2026-08-30. Every PMID was re-resolved through live PubMed E-utilities during the audit. Values preserve the study population, comparator and uncertainty; they should not be mixed across settings without recalibration.
1. Global burden
| Figure |
Population / method |
Source |
| 260 million prevalent asthma cases (95% uncertainty interval 227–298 million) in 2021 |
GBD 2021, 204 countries/territories |
GBD 2021 Asthma and Allergic Diseases Collaborators 2025, PMID 40147466 |
| 436,000 asthma deaths in 2021 |
GBD 2021 modeled estimate; the point estimate was retained, but an uncertainty interval not reproduced in the live record was removed during audit |
PMID 40147466 |
| Age-standardized prevalence fell 40.0% from 5,568.3 to 3,340.1 per 100,000, 1990–2021 |
GBD 2021 |
PMID 40147466 |
| 275 million projected cases (95% UI 224–330 million) in 2050 |
GBD forecast; population growth dominant |
PMID 40147466 |
| Modifiable factors accounted for 29.9% of asthma DALYs |
High BMI, occupational asthmagens, smoking and NO2 modeled |
PMID 40147466 |
| South Asia age-standardized asthma DALY rate 465.0 per 100,000 (95% UI 357.2–648.9) |
Highest GBD super-region estimate in 2021 |
PMID 40147466 |
2. Diagnostic accuracy and instability
FeNO diagnosis
| Metric |
Estimate |
Source |
| Sensitivity |
0.65 (95% CI 0.58–0.72) |
26 studies, 4,518 participants; Karrasch 2017, PMID 27388487 |
| Specificity |
0.82 (0.76–0.86) |
Same meta-analysis |
| Diagnostic odds ratio |
9.23 (6.55–13.01) |
Same meta-analysis |
| AUC |
0.80 (0.77–0.85) |
Same meta-analysis |
| Specificity increase per 10-ppb higher threshold |
OR 1.46 |
Same meta-regression |
| Figure |
Population / method |
Source |
| Current asthma ruled out in 203/613, 33.1% (95% CI 29.4–36.8) |
Canadian multicenter taper, spirometry and serial challenge |
Aaron 2017, PMID 28114551 |
| No evidence remained at 12 months in 181/613, 29.5% (25.9–33.1) |
Prospective follow-up |
PMID 28114551 |
| Serious cardiorespiratory alternative diagnosis in 12/613, 2.0% |
Same cohort |
PMID 28114551 |
| Objective airflow testing at original diagnosis: 43.8% when later ruled out vs 55.6% when confirmed |
Absolute difference 11.8% (2.1–21.5) |
PMID 28114551 |
3. Mild asthma and reliever trials
START
| Outcome |
Budesonide |
Placebo |
Effect |
| Participants with severe event |
117/3,597 |
198/3,568 |
HR 0.56 (95% CI 0.45–0.71) |
| Post-BD FEV1 advantage |
— |
— |
+1.48 percentage points year 1; +0.88 year 3 |
| Growth under age 11 |
— |
— |
−1.34 cm over 3 years |
Source: Pauwels 2003, PMID 12672309.
SYGMA 1
| Outcome |
Terbutaline PRN |
Budesonide–formoterol PRN |
Maintenance budesonide |
| Well-controlled weeks |
31.1% |
34.4% |
44.4% |
| Severe attacks/year |
0.20 |
0.07 |
0.09 |
| PRN budesonide–formoterol effect |
Reference |
RR 0.36 (0.27–0.49) |
vs maintenance RR 0.83 (0.59–1.16) |
| Median metered ICS/day |
0 |
57 μg |
340 μg |
Source: O'Byrne 2018, PMID 29768149.
SYGMA 2 and pragmatic trials
| Trial / outcome |
Estimate |
Source |
| SYGMA 2 severe attacks/year |
0.11 PRN ICS–formoterol vs 0.12 maintenance budesonide; RR 0.97, upper one-sided 95% limit 1.16 |
Bateman 2018, PMID 29768147 |
| SYGMA 2 median metered ICS |
66 vs 267 μg/day |
PMID 29768147 |
| Novel START exacerbations/year |
0.195 PRN budesonide–formoterol vs 0.400 albuterol; RR 0.49 (0.33–0.72) |
Beasley 2019, PMID 31112386 |
| CARE children attacks/year |
0.23 PRN budesonide–formoterol vs 0.41 salbutamol; RR 0.55 (0.35–0.86) |
Hatter 2025, PMID 41033330 |
| Pooled ICS–formoterol vs SABA severe attacks |
RR 0.65 (0.60–0.72); risk difference −10.3% (−11.8 to −8.3) |
Rayner 2025, PMID 39465893 |
| Pooled ICS–SABA vs SABA severe attacks |
RR 0.84 (0.73–0.95); risk difference −4.7% (−8.0 to −1.5) |
PMID 39465893 |
4. Severe asthma biologics
| Trial |
Population |
Primary attack result |
Other anchor |
| DREAM mepolizumab |
621 recurrent-attack eosinophilic severe asthma |
2.40/year placebo vs 1.24, 1.46, 1.15 across doses; reductions 48%, 39%, 52% |
No clear dose gradient |
| SIROCCO benralizumab |
Severe eosinophilic asthma |
Significant attack reduction in eosinophil-enriched population |
Lung-function response varied by regimen |
| LIBERTY QUEST dupilumab |
1,902 uncontrolled moderate-to-severe asthma |
Severe exacerbation RR 0.52 (95% CI 0.41–0.66) for 200-mg regimen vs placebo |
FEV1 +0.14 L vs placebo |
| NAVIGATOR tezepelumab |
1,061 severe uncontrolled asthma |
0.93 vs 2.10/year; RR 0.44 (0.37–0.53) |
FEV1 difference +0.13 L (0.08–0.18) |
| NAVIGATOR eosinophils <300 |
Prespecified subgroup |
1.02 vs 1.73/year; RR 0.59 (0.46–0.75) |
Broad but not biomarker-independent benefit |
5. Triple therapy
| Figure |
Evidence |
Source |
| Severe exacerbation: 22.7% triple vs 27.4% dual |
RR 0.83 (95% CI 0.77–0.90) |
20 RCTs, 11,894 participants; Kim 2021, PMID 34009257 |
| Symptom/QOL changes |
Average differences did not reach minimal important differences |
Same meta-analysis |
6. Preschool and childhood asthma
| Figure |
Population |
Source |
| Daily medium-dose ICS vs placebo severe attacks |
RR 0.70 (95% CI 0.61–0.79), NNT 9 |
22 trials, 4,550 preschool children; Kaiser 2016, PMID 27230765 |
| Persistent-asthma subgroup |
RR 0.56 (0.46–0.70), NNT 11 |
Same meta-analysis |
| Daily ICS vs montelukast |
RR 0.59 (0.38–0.92) |
One trial within same review |
| MIST daily vs intermittent budesonide |
0.97 (0.76–1.22) vs 0.95 (0.75–1.20) OCS-requiring attacks/year |
278 high-risk preschoolers; Zeiger 2011, PMID 22111718 |
| CAMP hospitalization |
2.5 vs 4.4 per 100 person-years, budesonide vs placebo |
1,041 children, 4–6 years; PMID 11027739 |
| CAMP urgent visits |
12 vs 22 per 100 person-years |
PMID 11027739 |
| CAMP height gain |
1.1 cm less with budesonide |
PMID 11027739 |
| ICS >12 months, first-year growth velocity |
−0.48 cm/year (95% CI −0.66 to −0.29) |
16 RCTs; Loke 2015, PMID 26191797 |
| Adult height, budesonide trial |
−1.20 cm (−1.90 to −0.50) |
Same systematic review |
| CAMP early-adult clinical remission |
26.0% |
879 participants; Wang 2019, PMID 30445065 |
| CAMP strict remission |
15.0% |
741 with airway-responsiveness data; PMID 30445065 |
7. Inhaler technique and adherence
| Figure |
Evidence |
Source |
| Overall device errors |
50–100% across included studies |
Chrystyn 2017, PMID 28373682 |
| Critical device errors |
14–92%; heterogeneity generally >90% |
PMID 28373682 |
| Education and critical errors |
RR 0.28 (95% CI 0.17–0.47) |
Marko 2025, PMID 40102397 |
| Education and any dry-powder error |
RR 0.38 (0.21–0.70) |
PMID 40102397 |
| Education and any MDI error |
RR 0.16 (0.11–0.23) |
PMID 40102397 |
| Mean ICS adherence |
22–63% across studies |
Bårnes 2015, PMID 25118311 |
| Pediatric adherence intervention |
Hedges g 0.39 (0.24–0.54) post-intervention; follow-up g 0.38 (−0.08 to 0.83) |
Fidler 2021, PMID 34343294 |
| Pharmacist-led adherence intervention |
SMD 0.49 (0.35–0.64) |
Mes 2018, PMID 29976652 |
| Electronic-monitor adherence |
Random-effects SMD 0.41 (0.22–0.60) |
Garin 2023, PMID 36986513 |
8. Supported self-management
| Outcome |
Effect |
Source |
| Hospitalization |
RR 0.64 (95% CI 0.50–0.82) |
36 trials; Gibson 2003, PMID 12535399 |
| Emergency visits |
RR 0.82 (0.73–0.94) |
Same review |
| Unscheduled clinician visits |
RR 0.68 (0.56–0.81) |
Same review |
| Work/school absence |
RR 0.79 (0.67–0.93) |
Same review |
| Nocturnal asthma |
RR 0.67 (0.56–0.79) |
Same review |
| Quality of life |
SMD 0.29 (0.11–0.47) |
Same review |
| School program ED visits |
OR 0.70 (0.53–0.92) |
Kneale 2019, PMID 30686788 |
| School program hospitalization |
SMD −0.19 (−0.35 to −0.04) |
Same review |
9. Biomarkers
| Marker strategy |
Effect |
Source |
| Sputum-guided therapy, ≥1 attack |
62 vs 82 per 100; OR 0.36 (0.21–0.62) |
Petsky 2018, PMID 29858277 |
| Adult FeNO-guided, ≥1 attack |
OR 0.61 (0.44–0.83) |
12 RCTs, 2,116 adults; Korevaar 2023, PMID 37293870 |
| Adult FeNO-guided attack rate |
RR 0.67 (0.54–0.82) |
Same review |
| Pediatric FeNO-guided, children with attacks |
RR 0.73 (0.63–0.84) |
23 RCTs; Wang 2020, PMID 32525611 |
| Pediatric FeNO-guided ICS dose |
+64.17 μg/day (53.59–74.75) |
Same review |
| Serum periostin diagnosis |
Sensitivity 0.68 (0.42–0.86), specificity 0.87 (0.76–0.93) |
Jia 2021, PMID 31738608 |
10. Comorbidity and mimics
| Figure |
Population / caveat |
Source |
| Laryngeal dysfunction prevalence |
25% (95% CI 15–37), I²=96%; selected asthma cohorts with objective laryngoscopy |
Lee 2020, PMID 31940470 |
| Bronchiectasis prevalence |
36.6% (307/839); selected CT-imaged cohorts |
Zhang 2021, PMID 33530179 |
| Bronchiectasis FEV1/FVC difference |
−2.71 percentage points (−3.72 to −1.69) |
Same meta-analysis |
| Bronchiectasis attack difference |
+0.68/year (0.03–1.33) |
Same meta-analysis |
| OSA prevalence in adult asthma |
49.5% (36.4–62.6) |
Kong 2017, PMID 28642543 |
| Asthma–OSA association |
OR 2.64 (1.76–3.52) |
Same meta-analysis |
| GERD–asthma exacerbation association |
OR 1.27 (1.18–1.35) |
32 studies, 1.61 million; Mallah 2022, PMID 34448255 |
| Allergic-rhinitis association with asthma |
OR 4.24 (3.82–4.71) |
Rogliani 2023, PMID 36889783 |
11. Pregnancy
| Outcome in maternal asthma |
Relative risk (95% CI) |
Source |
| Low birthweight |
1.46 (1.22–1.75) |
Murphy 2011, PMID 21749633 |
| Small for gestational age |
1.22 (1.14–1.31) |
Same meta-analysis |
| Preterm delivery |
1.41 (1.22–1.61) |
Same meta-analysis |
| Pre-eclampsia |
1.54 (1.32–1.81) |
Same meta-analysis |
| Preterm delivery under active management |
1.07 (0.91–1.26) |
Subgroup, same meta-analysis |
| Exacerbation risk: obesity |
RR 1.25 (1.15–1.37) |
Robijn 2022, PMID 35705210 |
| Exacerbation risk: smoking |
RR 1.35 (1.04–1.75) |
Same review |
| Exacerbation risk: depression/anxiety |
RR 1.42 (1.27–1.59) |
Same review |
| Exacerbation risk: moderate–severe vs mild |
RR 3.44 (2.03–5.83) |
Same review |
12. SABA and systemic steroid safety
| Figure |
Evidence |
Source |
| SABA overuse prevalence |
30% collected ≥3 canisters in baseline year |
Swedish cohort n=365,324; Nwaru 2020, PMID 31949111 |
| Attack risk, 3–5 canisters |
HR 1.26 (1.24–1.28) |
Same cohort |
| Attack risk, 6–10 canisters |
HR 1.44 (1.41–1.46) |
Same cohort |
| SABA ≥3 canisters and mortality |
RR 2.04 (1.37–3.04) |
27-study meta-analysis; Tsao 2025, PMID 40491263 |
| Systemic steroid and osteoporosis/fracture |
adjusted HR 3.11 (1.87–5.19) |
Matched cohort; Price 2018, PMID 30214247 |
| Systemic steroid and pneumonia |
HR 2.68 (2.30–3.11) |
Same cohort |
| OCS and osteoporosis |
pooled HR 1.76 (1.48–2.09) |
Chalitsios 2021, PMID 33799052 |
| Severe-asthma registry ≥500 mg OCS/year |
44% |
Politis 2024, PMID 38622806 |
| Severe-asthma registry ≥1,000 mg OCS/year |
32% |
Same registry |
13. Inequity and patient priorities
| Figure |
Evidence |
Source |
| Lowest vs highest income attack odds |
OR 1.25 (1.13–1.37) |
Gassasse 2025, PMID 40688041 |
| Same, children |
OR 1.36 (1.23–1.50) |
Same meta-analysis |
| Same, adults |
OR 1.19 (1.05–1.33) |
Same meta-analysis |
| Lower SES and ED attendance |
OR 1.61 (1.40–1.84) |
Redmond 2022, PMID 34673047 |
| Lower SES and hospitalization |
OR 1.63 (1.34–1.99) |
Same review |
| Patient goals aligning with clinician goals |
53% |
Severe-asthma cohorts; Mulvey 2021, PMID 33577946 |
| Severe Asthma Questionnaire test–retest ICC |
0.93 |
Hyland 2018, PMID 29794132 |
Known conflicts and interpretation caveats
- GBD uncertainty intervals are modeled uncertainty, not sampling confidence intervals.
- Trial relative effects require the comparator’s baseline event rate for individual absolute benefit.
- Observational SABA/OCS associations include confounding by disease severity, but dose-response supports safety action.
- Diagnostic sensitivity/specificity changes with threshold, spectrum, treatment and reference standard.
- Biomarker thresholds are drug-, assay-, age- and population-specific.
- Prevalence estimates from specialty or imaged cohorts should not be applied to community asthma.
- “Remission” definitions differ and must specify on-treatment versus off-treatment state.