Content
Introduction
Pneumonia background
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Environmental – poverty, pollution, crowding, cigarette smoke exposure, season,
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Maternal – low education, HIV, psychosocial distress,
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Child – nutrition, male sex, HIV, preterm birth, low birthweight, lack of breastfeeding, and
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Health system – lack of access to preventive treatment (immunization).
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in which periods certain subgroups are at high(er) risks, and
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how the relative risks possibly evolve over time.
Methodology
The Drakenstein child health study data
Possible risk factors
Statistical models
Binary covariates models
Seasonality models
Estimation
Statistical analysis and model selection
Results
Data description
Risk factors | Mbekweni n (%) | TC Newman n (%) |
---|---|---|
Total | 628 (55.2) | 509 (44.8) |
HU | 397 (63.2) | 493 (96.9) |
HEU | 228 (36.3) | 16 (3.1) |
Girls | 316 (50.3) | 232 (45.6) |
Boys | 312 (49.7) | 277 (54.4) |
Not low WfL | 386 (61.5) | 299 (58.7) |
Low WfL | 174 (27.7) | 154 (30.3) |
Not preterm birth | 522 (83.1) | 425 (83.5) |
Preterm birth | 106 (16.9) | 84 (16.5) |
Not low birthweight | 554 (88.2) | 414 (81.3) |
Low birthweight | 74 (11.8) | 95 (18.7) |
Lower SES | 356 (56.7) | 211 (41.5) |
Higher SES | 272 (43.3) | 298 (58.5) |
Uncrowded | 487 (77.5) | 344 (67.6) |
Crowded | 141 (22.5) | 165 (32.4) |
No maternal smoking | 504 (80.2) | 232 (45.6) |
Maternal smoking | 91 (14.4) | 261 (51.3) |
Unexposed to Indoor air pollution | 311 (49.5) | 387 (76.0) |
Exposed to indoor air pollution | 132 (21.0) | 7 (1.4) |
High maternal education | 239 (38.1) | 206 (40.5) |
Low maternal education | 389 (61.9) | 303 (59.5) |
The estimated baseline hazard and baseline cumulative incidence proportion
Model 1 | Model 2 | ||||
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\(\overline {IR}\) (95% CI) | \(\widehat {HR}\ \) (95% CI; p-value) | \(\overline {IR}\) (95% CI) | \(\widehat {\overline {HR(t)}}\) (95% CI; p-value) | EDF (p-value) | |
HU | 0.29 (0.26, 0.32) | 0.29 (0.26, 0.33) | |||
HEU | 0.42 (0.35, 0.51) | 1.49 (1.21, 1.83; p<0.001) | 0.40 (0.33, 0.48) | 1.37 (1.10, 1.71; p=0.004) | 1.00 (p=0.036) |
Girls | 0.25 (0.22, 0.29) | 0.25 (0.22, 0.29) | |||
Boys | 0.38 (0.34, 0.43) | 1.53 (1.28, 1.84; p<0.001) | 0.37 (0.33, 0.43) | 1.48 (1.22, 1.79; p<0.001) | 1.00 (p=0.261) |
Not low WfL | 0.30 (0.26, 0.33) | 0.29 (0.25, 0.33) | |||
Low WfL | 0.29 (0.25, 0.35) | 0.99 (0.81, 1.22; p=0.926) | 0.31 (0.26, 0.37) | 1.07 (0.87, 1.33; p=0.522) | 1.00 (p=0.023) |
Mbekweni | 0.34 (0.30, 0.38) | 0.33 (0.29, 0.38) | |||
TC Newman | 0.29 (0.25, 0.33) | 0.85 (0.71, 1.02; p=0.074) | 0.29 (0.25, 0.34) | 0.89 (0.73, 1.07; p=0.212) | 1.00 (p=0.162) |
Not preterm birth | 0.30 (0.27, 0.33) | 0.29 (0.26, 0.33) | |||
Preterm birth | 0.42 (0.34, 0.51) | 1.41 (1.12, 1.77; p=0.003) | 0.42 (0.34, 0.52) | 1.43 (1.12, 1.81; p=0.003) | 1.00 (p=0.752) |
Not low birthweight | 0.29 (0.26, 0.32) | 0.29 (0.26, 0.32) | |||
Low birthweight | 0.46 (0.37, 0.56) | 1.56 (1.23, 1.97; p<0.001) | 0.47 (0.37, 0.58) | 1.61 (1.26, 2.05; p<0.001) | 2.11 (p=0.168) |
Lower SES | 0.37 (0.32, 0.41) | 0.37 (0.33, 0.42) | |||
Higher SES | 0.26 (0.23, 0.30) | 0.72 (0.60, 0.87; p<0.001) | 0.26 (0.22, 0.30) | 0.69 (0.57, 0.83; p<0.001) | 1.00 (p=0.127) |
Uncrowded | 0.30 (0.27, 0.34) | 0.30 (0.27, 0.34) | |||
Crowded | 0.34 (0.29, 0.41) | 1.14 (0.94, 1.39; p=0.177) | 0.35 (0.29, 0.41) | 1.16 (0.95, 1.43; p=0.152) | 1.01 (p=0.635) |
No maternal smoking | 0.28 (0.25, 0.32) | 0.28 (0.25, 0.32) | |||
Maternal smoking | 0.38 (0.33, 0.45) | 1.35 (1.12, 1.64; p=0.002) | 0.39 (0.33, 0.45) | 1.38 (1.13, 1.68; p=0.001) | 1.00 (p=0.537) |
Indoor air pollution unexposed | 0.32 (0.28, 0.36) | 0.32 (0.28, 0.36) | |||
Indoor air pollution exposed | 0.27 (0.21, 0.36) | 0.85 (0.63, 1.15; p=0.279) | 0.26 (0.20, 0.35) | 0.83 (0.61, 1.12; p=0.224) | 2.00 (p=0.337) |
High maternal education | 0.27 (0.23, 0.32) | 0.28 (0.24, 0.33) | |||
Low maternal education | 0.34 (0.30, 0.38) | 1.24 (1.03, 1.50; p=0.022) | 0.33 (0.30, 0.38) | 1.18 (0.97, 1.44; p=0.093) | 1.47 (p=0.218) |
Analysis of binary risk factors
Relative risks (i.e. hazard ratios) over time
Estimated incidence over time
Estimated cumulative incidence over time
Analysis of seasonal effects
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Autumn/Fall – 1 March to 31 May (day 60 – day 151)
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Winter – 1 June to 31 August (day 152 – day 243)
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Spring – 1 September to 30 November (day 244 – day 334)
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Summer – 1 December to 28/29 February (day 335 – day 365; day 1 – day 59)