Overall

Between the years of 1999 and 2020, there were 3,064,049 reported deaths related to chronic lower respiratory diseases in this study population.

Overall, the age-adjusted mortality rate (AAMR) decreased significantly from 70 (95% CI 69.6 to 70.4) in 1999 to 64.2 (95% CI 64.2 to 64.3) in 2020 with an AAPC of -0.93* (95% CI -1.08 to -0.76) (Supplemental Table 2; Supplemental Fig. 1). From 1999 to 2017, the APC in AAMR was − 0.46* (95% CI − 0.64 to -0.22), which then increased significantly from 2017 to 2020 to -3.70* (95% CI -6.04 to -1.86) (Fig. 1).

By the end of the study period, the highest mortality rate was seen in the elderly population (ages 85 or older), with a CMR of 612.6 in 2020. The largest mortality rates were also seen in non-Hispanic White males, with an AAMR OF 68.4 in 2020. Although males demonstrated the highest overall mortality in the study with declining trends, it is important to recognize that females, although having overall lower mortality, did not demonstrate the same declining trend until the latter half of the 2010s. Lastly, regionally, the males in both the Midwest and South had the greatest AAMR of 70.2 and 68.4, respectively. Males in rural populations had the highest mortality rate of all populations, with an AAMR of 87.4.

Demographic differencesGender stratified

In men, the AAMR decreased from 90.5 (95% CI 89.8 to 91.2) in 1999 to 61.9 (95% CI 61.4 to 62.3) in 2020, with an AAPC of -1.59* (95% CI -1.79 to -1.22) (Supplemental Table 2; Supplemental Fig. 1). The APC in AAMR was − 1.28 (95% CI -1.50 to 0.85) from 1999 to 2018, which then accelerated significantly from 2018 to 2020 to -4.48* (95% CI -6.65 to -1.45) (Fig. 1).

In women, the AAMR overall decreased from 58.1 (95% CI 57.6 to 58.5) in 1999 to 51.7 (95% CI 51.4 to 52.1) in 2020, with an AAPC of -0.49* (95% CI -0.74 to -0.25) (Supplemental Table 2; Supplemental Fig. 1). However, the APC in AAMR was 0.09 (95% CI -0.08 to 0.34) from 1999 to 2017, which finally trended downward from 2017 to 2020 to -3.95* (95% CI -7.52 to -1.51) (Fig. 1).

Fig. 1

(a) Overall and gender stratified data regarding mortality rates associated with chronic lower respiratory diseases in the United States between 1999 and 2020. *Indicates the APC is significantly different from 0. (b) Stratified data by racial/ethnic groups regarding mortality rates associated with chronic lower respiratory diseases in the United States between 1999 and 2020. *Indicates the APC is significantly different from 0

Race stratified

For chronic lower respiratory diseases, the highest mortality was seen in the non-Hispanic (NH) White population, which remained the highest throughout the years of 1999–2020. The AAMR decreased slightly from 74.6 (95% CI 74.1 to 75.0) in 1999 to 71.2 (95% CI 71.1 to 71.3) in 2020, with an AAPC of -0.60 (95% CI -0.84 to -0.34) (Supplemental Table 3; Supplemental Fig. 2a). The AAMR APC was − 0.11 (95% CI -0.29 to 0.17) from 1999 to 2017, which accelerated to -3.47* (95% CI -6.88 to -1.08) from 2017 to 2020 (Supplemental Fig. 2b). Non-Hispanic Asian or Pacific Islander populations remained as the lowest mortality racial group with an AAMR that decreased significantly from 30.0 (95% CI 28.1 to 31.8) in 1999 to 16.2 (95% CI 15.6 to 16.9) in 2020 with an APC of -2.63* (95% CI -2.90 to -2.33) (Supplemental Table 3; Supplemental Fig. 2a). Non-Hispanic Black or African American populations had a steady AAMR of 51.7 (95% CI 50.5 to 52.9) in 1999 to 46.0 (95% CI 45.1 to 46.8) in 2020. With an AAPC of -0.54 (95% CI -0.80 to -0.17), this population had a mortality rate between NH White, the highest AAMR racial group, and NH Asian or Pacific Islander, the lowest AAMR racial group (Supplemental Fig. 2b). The AAMR APC was − 2.15* (95% CI -6.15 to -0.48) from 1999 to 2004, which decelerated to -0.03 (95% CI -0.30 to 1.47) from 2004 to 2020 (Supplemental Fig. 2b).

Race and gender stratified

On further stratification of both gender and race, the highest AAMR was seen in NH White males with a profound decrease in AAMR of 94.6 (95% CI 93.8 to 95.4) in 1999 to 68.4 (95% CI 67.9 to 69.0) in 2020 (Fig. 2; Supplemental Table 4). With an AAPC of -1.33* (95% CI -1.57 to -0.97), the 1999–2018 APC was − 1.00 (95% CI -1.18 to 0.21), and the 2018–2020 APC accelerated to -4.52* (95% CI -7.04 to -1.17) (Supplemental Fig. 3a). NH Asian or Pacific Islander males had the lowest mortality rate with an APC of -3.19* (95% CI -3.45 to -2.88) (Supplemental Fig. 3a).

For females, NH White females had a significant increase in AAMR from 62.9 (95% CI 62.4 to 63.5) in 1999 to 68.3 (95% CI 67.8 to 68.8) in 2017, followed by a decrease in AAMR to 60.1 (95% CI 59.6 to 60.5) in 2020 (Fig. 2; Supplemental Table 4). The 1999–2017 APC was 0.47* (95% CI 0.26 to 0.74) before finally assuming a downward trend from 2017 to 2020 with an APC of -3.85* (95% CI -6.49 to -1.78) (Supplemental Fig. 3b). NH American Indian or Alaska Native females followed a similar trend with marked increase in AAMR from 50.8 (95% CI 43.6 to 58) in 1999 to 59.1 (95% CI 53.7 to 64.4) in 2017 (1999–2017 APC 0.91 (95% CI 0.43 to 1.70)), followed by a decreasing trend in AAMR to 43.6 (95% CI 39.3 to 47.8) by 2020 (2017–2020 APC − 8.19 (95% CI -16.28 to -3.30)) (Supplemental Fig. 3b). NH Black or African American females demonstrated a decrease in AAMR from 1999 to 2004 with an APC of -0.96 (95% CI -4.73 to 0.51); however, between 2004 and 2020, this population illustrated an increase in AAMR with an APC of 0.78* (95% CI 0.50 to 2.19) (Fig. 2, Supplemental Fig. 3b). NH Asian or Pacific Islanders females remained with the lowest mortality rate with an APC of -1.81* (95% CI -2.19 to -1.32) (Supplemental Fig. 3b).

Fig. 2

Data stratified by racial/ethnic groups and gender for chronic lower respiratory diseases related mortality in the United States between 1999 and 2020. *Indicates the APC is significantly different from 0

Age group stratified

Patients who are 85 years of age or older had the highest crude mortality rate, with a slight increase from 646.0 (95% CI 638.2 to 653.7) in 1999 to 700.6 (95% CI 694.1 to 707) in 2017, before decreasing to 612.6 (95% CI 606.7 to 618.6) in 2020 (Supplemental Table 5; Supplemental Fig. 4a). The 1999–2017 APC was 0.40* (95% CI 0.18 to 0.72) and the 2017–2020 APC was − 4.05* (95% CI -7.65 to -1.51) (Supplemental Fig. 4b). Followed by the 85 years or older age group, patients between 70 and 84 years of age had the second highest crude mortality rate, which decreased from 326.2 (95% CI 323.8 to 328.6) to 230.2 (95% CI 228.6 to 231.9) between 1999 and 2020 (Supplemental Table 5; Supplemental Fig. 4a). With an AAPC of -1.53* (95% CI -1.78 to -1.28), the 1999–2016 APC was − 0.81* (95% CI -1.04 to -0.50) and the 2016–2020 APC was − 4.55* (95% CI -7.87 to -2.76) (Supplemental Fig. 4b).

Regional variationCensus region-based differences

In 1999, AAMR was highest in the West at 75.7 (95% CI 74.8 to 76.6), followed by the Midwest at 71.4 (95% CI 70.6 to 72.2) and the South at 71.6 (95% CI 71 to 72.3), with the Northeast region having the lowest AAMR at 60.6 (95% CI 59.8 to 61.4) (Supplemental Table 6). The Midwest and South have remained stable between 1999 and 2017 with an APC of 0.08 (95% CI -0.16 to 0.63) in the Midwest and − 0.09 (95% CI -0.28 to 0.19) in the South (Supplemental Table 6; Supplemental Fig. 5a). However, within this same period, AAMR in the West has dropped significantly below the Midwest and South with an APC of -1.50 (95% CI -1.65 to -1.20) (Supplemental Fig. 5b). Between 2017 and 2020, there has been a regional decline in AAMR in all four regions. By the end of the study, the highest AAMR was seen in the Midwest at 63.0 (95% CI 62.4 to 63.7), followed closely by the South at 62.3 (95% CI 61.8 to 62.7), then the West at 49.4 (95% CI 48.8 to 50), with the Northeast region still having the lowest AAMR at 47.0 (95% CI 46.4 to 47.6) (Supplemental Fig. 5b).

Gender and census region-based differences

Females in the Midwest region demonstrated an increase in AAMR from 58.4 (95% CI 57.5 to 59.4) in 1999 to 65.4 (95% CI 64.5 to 66.4) in 2015 (1999 to 2015 APC 0.86*), before decreasing to 58.1 (95% CI 57.2 to 58.9) in 2020 (2015 to 2020 APC − 2.02*) (Fig. 3; Supplemental Table 7; Supplemental Fig. 6a). Similar patterns were seen with females in the Southern region with increases in AAMR from 57.9 (95% CI 57.1 to 58.7) in 1999 to 64.6 (95% CI 63.9 to 65.3) in 2017 (1999 to 2017 APC 0.60*), before decreasing to 57.6 (95% CI 57.0 to 58.2) in 2020 (2017 to 2020 APC − 3.76*) (Fig. 3; Supplemental Table 7; Supplemental Fig. 6a). Although females in the West region began the study with the highest AAMR of 65.7 (95% CI 64.6 to 66.8), it decreased significantly to 45.3 (95% CI 44.6 to 46) by 2020 (1999 to 2017 APC − 1.19*, 2017 to 2020 APC − 4.45*) (Fig. 3; Supplemental Table 7; Supplemental Fig. 6a). Females in the Northeast region remained the lowest with an AAMR of 51.1 (95% CI 50.2 to 52) in 1999 to 40.5 (95% CI 39.7 to 41.2) in 2020 (Fig. 3; Supplemental Table 7; Supplemental Fig. 6a).

On average, in male populations throughout all of the regions, there were significant decreases in AAMR; however, in the Midwest and South, the male populations had higher AAMRs of 70.2 (95% CI 69.1 to 71.2) in the Midwest and 68.4 (95% CI 67.7 to 69.2) in the South (Fig. 3; Supplemental Table 7; Supplemental Fig. 6b). Northeast males had the lowest AAMR of 47.7 (95% CI 46.8 to 48.7) (Fig. 3; Supplemental Table 7; Supplemental Fig. 6b). The Midwest male population, although still decreasing in AAMR, had the lowest reduction in mortality with an AAPC of -1.20* (95% CI -1.45 to -0.83) compared to -1.38* (95% CI -1.66 to -0.90) in the Southern region, -1.80* (95% CI -2.01 to -1.59) in the Northeast region, and − 2.08* (95% CI -2.30 to -1.85) in the Western region (Fig. 3; Supplemental Table 7; Supplemental Fig. 6b).

Fig. 3

(a) Data stratified by region regarding mortality rates associated with chronic lower respiratory diseases in the United States between 1999 and 2020. *Indicates the APC is significantly different from 0. (b) Data stratified by region and gender regarding mortality rates associated with chronic lower respiratory diseases in the United States between 1999 and 2020. *Indicates the APC is significantly different from 0

State-level differences

Large state-to-state variations in AAMR exist within the United States. The lowest overall AAMR is 29.5 (95% CI 28.8 to 30.2) in Hawaii, while the highest AAMR is 95.1 (95% CI 94.1 to 96.1) in West Virginia (Supplemental Table 8). Other states included in the ≤ 10th percentile of chronic lower respiratory disease-related mortality include the District of Columbia (AAMR of 37.2), New Jersey (AAMR of 47.4), New York (AAMR of 47.9), Connecticut (AAMR of 50), and Utah (AAMR of 51.3). The states included in the ≥ 90th percentile of chronic lower respiratory disease-related mortality also include Indiana (AAMR of 83.7), Arkansas (AAMR of 85.5), Wyoming (AAMR of 89.7), Kentucky (AAMR of 94.1, Oklahoma (AAMR of 94.2), and West Virginia (AAMR of 95.1).

The state of Alaska had the largest decreased rate of change when comparing the AAMR from 1999 to 2020 of -40.2 with an APC of -2.02* (95% CI -2.56 to -1.43) (Supplemental Table 9; Supplemental Fig. 7a, 8a). Followed by Wyoming and Washington, with a decrease in AAMR of -34.5 (AAPC of -1.06* (95% CI -1.59 to -0.50)) in Wyoming, and − 33.3 (AAPC of -2.36* (95% CI -2.91 to -1.91)) in Washington (Supplemental Table 10; Supplemental Fig. 7b). Arkansas had the most increase in AAMR by 21.2 (AAPC of 1.29* (95% CI 0.89 to 1.90)) (Supplemental Table 10; Supplemental Fig. 8a, 8b). Hawaii demonstrated the lowest AAMR throughout 1999–2020 decreasing from 36.9 to 27.4 with a change of AAMR of -9.5 from 1999 to 2020 (Fig. 4).

Fig. 4

Data stratified by state regarding total change in AAMR per 100,000 from 1999 to 2020 for chronic lower respiratory diseases-related mortality in the United States

Rural versus urban differences

Throughout the study period, urban populations had average AAMRs that were lower at 51.7 (95% CI 51.4 to 52) compared to rural areas at 78.4 (95% CI 77.6 to 79.2) (Fig. 5, Supplemental Table 11). Overall, the urban population decreased in AAMR with an AAPC of -1.18* (95% CI -1.44 to -0.90) compared to rural areas at an AAPC of 0.25* (95% CI 0.03 to 0.49). In 1999, urban females and rural females had similar AAMRs, with urban females at 58.2 (95% CI 57.7 to 58.7) and rural females at 57.9 (95% CI 56.8 to 58.9). However, the difference widened with urban females overall having a decrease in mortality with an AAPC of -0.81* (95% CI -1.06 to -0.52), the 1999–2017 APC was − 0.23 (95% CI -0.43 to -0.08) and the 2017–2020 APC was − 4.26* (95% CI -7.74 to -1.80) (Supplemental Fig. 9). In contrast, rural females had a slight increase in mortality with an AAPC of 1.03* (95% CI 0.76 to 1.27), the 1999–2017 APC was 1.64* (95% CI 1.44 to 1.92) and the 2017–2020 APC was − 2.57* (95% CI -6.23 to -0.23) (Supplemental Fig. 9). Both urban and rural males demonstrated decreases in mortality throughout the study period with AAPCs of -1.79* (95% CI -2.00 to -1.44) in urban males and − 0.60* (95% CI -0.79 to -0.38) in rural males (Supplemental Fig. 9).

Fig. 5

Data stratified by gender and urban-rural classifications for chronic lower respiratory diseases related mortality in the United States between 1999 and 2020. *Indicates the APC is significantly different from 0