Volume 30, Number 1—January 2024
Research
Population-Based Study of Pertussis Incidence and Risk Factors among Persons >50 Years of Age, Australia
, Ken L. Chin, Adrienne Guignard, Leah-Anne Latorre, C. Raina MacIntyre, Brittany Schoeninger, and Sumitra Shantakumar
Table 1
Baseline patient characteristics for persons ≥50 years of age with pertussis identified in the overall study population, Australia*
| Characteristics | Year
|
p value† | |||||
|---|---|---|---|---|---|---|---|
|
2015, n = 253 |
2016, n = 251 |
2017, n = 219 |
2018, n = 162 |
2019, n = 148 |
Total, n = 992 |
||
| Age, y | |||||||
| Mean (95% CI) | 62.5 (61.3–63.7) | 63.1 (61.9–64.3) | 63.1 (61.9–64.2) | 65 (63.4–66.5) | 63.8 (62.3–65.4) | 63.3 (62.7–63.9) | 0.22 |
| Median (IQR)
|
61
(54–68)
|
61
(54–68)
|
63
(56.5–69.5)
|
63
(56–70)
|
63
(55.5–70.5)
|
62
(55.5–68.5)
|
0.15
|
| Sex‡ | |||||||
| M | 91 (36) | 77 (31) | 73 (33) | 56 (35) | 49 (33) | 332 (33) | 0.61 |
| F
|
162 (64)
|
173 (69)
|
146 (67)
|
105 (65)
|
99 (67)
|
658 (67)
|
0.61
|
| Smoking status | |||||||
| Never | 101 (41) | 107 (45) | 94 (44) | 67 (41) | 70 (47) | 433 (44) | 0.61 |
| Past | 49 (20) | 45 (19) | 53 (25) | 51 (31) | 33 (22) | 216 (22) | 0.46 |
| Current | 15 (6) | 22 (9) | 17 (8) | 14 (9) | 9 (6) | 75 (8) | 0.61 |
| Unknown
|
79 (32)
|
63 (27)
|
51 (24)
|
30 (19)
|
36 (24)
|
268 (27)
|
0.13
|
| Alcohol consumption/d§ | |||||||
| None | 94 (39) | 97 (41) | 86 (40) | 75 (46) | 75 (51) | 426 (43) | 0.09 |
| ≤1 unit | 39 (16) | 32 (14) | 35 (16) | 28 (17) | 28 (19) | 161 (16) | 0.13 |
| >1 unit | 18 (7) | 12 (5) | 14 (7) | 15 (9) | 18 (12) | 76 (8) | 0.13 |
| Unknown
|
93 (38)
|
96 (41)
|
80 (37)
|
44 (27)
|
27 (18)
|
329 (33)
|
0.09
|
| Vaccination history¶ | |||||||
| Pertussis | 36 (14) | 29 (12) | 36 (16) | 31 (19) | 25 (17) | 140 (14) | 0.22 |
| Influenza | 2 (1) | 49 (20) | 68 (31) | 71 (44) | 59 (40) | 241 (24) | 0.09 |
| Pneumococcal
|
8 (3)
|
11 (4)
|
15 (7)
|
11 (7)
|
21 (14)
|
60 (7)
|
0.04
|
| Residence | |||||||
| New South Wales | 83 (34) | 54 (23) | 51 (24) | 34 (21) | 49 (33) | 282 (29) | 0.81 |
| Victoria | 64 (26) | 78 (33) | 71 (33) | 40 (25) | 29 (20) | 258 (26) | 0.31 |
| Queensland | 29 (12) | 26 (11) | 27 (13) | 15 (9) | 9 (6) | 111 (11) | 0.22 |
| Western Australia | 21 (9) | 17 (7) | 15 (7) | 12 (7) | 7 (5) | 70 (7) | 0.10 |
| South Australia | 12 (5) | 10 (4) | 6 (3) | 3 (2) | 6 (4) | 38 (4) | 0.31 |
| Tasmania | 5 (2) | 11 (5) | 12 (6) | 35 (22) | 30 (20) | 89 (9) | 0.09 |
| Australian Capital Territory | 26 (11) | 31 (13) | 23 (11) | 14 (9) | 11 (7) | 105 (11) | 0.13 |
| Northern Territory
|
4 (2)
|
10 (4)
|
10 (5)
|
9 (6)
|
7 (5)
|
39 (4)
|
0.13
|
| Comorbidities# | |||||||
| COPD | 41 (16) | 51 (20) | 40 (18) | 38 (23) | 25 (17) | 185 (19) | 0.81 |
| Asthma | 25 (10) | 35 (14) | 27 (12) | 24 (15) | 16 (11) | 117 (12) | 0.81 |
| CVD | 101 (40) | 111 (44) | 96 (44) | 78 (48) | 57 (39) | 409 (41) | 0.61 |
| Heart failure | 4 (2) | 4 (2) | 3 (1) | 2 (1) | 9 (6) | 16 (2) | 0.61 |
| Diabetes mellitus | 32 (13) | 32 (13) | 36 (16) | 34 (21) | 18 (12) | 144 (14) | 0.61 |
| History of stroke | 3 (1) | 3 (1) | 3 (2) | 2 (1) | 9 (6) | 21 (2) | 0.27 |
| Chronic kidney disease | 5 (2) | 4 (2) | 10 (5) | 4 (2) | 5 (3) | 27 (3) | 0.58 |
| Cancer, active or remission | 23 (9) | 45 (18) | 32 (15) | 29 (18) | 22 (15) | 136 (14) | 0.79 |
*Values are no. (%) except as indicated. Variables were defined as those at baseline (i.e., restricted to those recorded during the study period or until the time of pertussis diagnosis). COPD, chronic obstructive pulmonary disease; CVD, cardiovascular disease (except heart failure); IQR, interquartile range. †Pearson χ2 or Fisher exact test for categorical variables, Student t-test/Wilcoxon/Kruskal Wallis tests for continuous variables, as appropriate. There were significant differences in smoking status, alcohol consumption, state of residence (Western Australia, Australian Capital Territory), COPD, and diabetes between males and females. ‡Two patients had sex documented as unknown. §One unit of alcohol is defined as containing 10 g of alcohol according to Australia’s national alcohol guidelines. ¶History of pertussis immunization was defined as the presence of pertussis immunization record throughout the study period, as recorded in the Australia general practitioner electronic medical records database. #History of CVD, chronic kidney disease, and cancer were defined as those at baseline and were restricted to those recorded during the study period, or until the time of pertussis diagnosis, as applicable.