risk factors for severe acute lower respiratory tract infection in under-five children

8/10/2019 Risk Factors for Severe Acute Lower Respiratory Tract Infection in Under-Five Children

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Original Articles

Indian Pediatrics 2001; 38: 1361-1369

Risk Factors for Severe Acute Lower Respiratory Tract Infection in Under-Five Children


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S. Broor+, R.M. Pandey*, M. Ghosh, R.S. Maitreyi+, Rakesh Lodha,Tanu Singhal and S.K. Kabra

From the Department of Pediatrics, *Biostatistics and +Microbiology, All India Institute of MedicalSciences, Ansari Nagar, New Delhi 110 029, India.

Correspondence to: Dr. S.K. Kabra, Additional Professor, Department of Pediatrics, All India Institute ofMedical Sciences, Ansari Nagar, New Delhi 110 029, India. E-mail: skkabra@ hotmail.com

Manuscript received: May 2, 2001, Initial review completed: June 13, 2001,Revision accepted: August 22, 2001.

Background :Acute lower respiratory infection (ALRTI) is the leading cause of death in children belowfive years of age. Identification of modifiable risk factors of severe ALRTI may help in reducing the burdenof disease. Methods:A hospital based case control study was undertaken to determine risk factorsassociated with severe lower respiratory tract infection (LRTI) in under-five children. A case definition ofsevere ALRTI as given by World Health Organization (WHO) was used for cases. Healthy childrenattending Pediatrics out patient department for immunization during study period were enrolled ascontrols. Details of potential risk factors in cases and controls were recorded in pre-designed

proforma.Resul ts :512 children including 201 cases and 311 controls were enrolled in the study. Onstepwise logistic regression analysis it was found that lack of breastfeeding (OR: 1.64; 95% CI: 1.232.17); upper respiratory infection in mother (OR: 6.53; 95% CI: 2.7315.63); upper respiratory infection insiblings (OR: 24; 95% CI: 7.874.4); severe malnutrition (OR: 1.85; 95% CI: 1.143.0); cooking fuel otherthan liquid petroleum gas (OR: 2.5; 95% CI: 1.514.16); inappropriate immunization for age (OR: 2.85;95% CI 1.595.0) and history of LRTI in the family (OR 5.15, 95% CI 3.08.8) were the significantcontributors of ALRTI in children under five years. Sex of the child, age of the parents, education of theparents, number of children at home, anemia, inadequate caloric intake, type of housing were notdocumented to be significant risk factors of ALRTI.Conclusion:Lack of breast-feeding, upper respiratoryinfection in mother, upper respiratory infection in siblings, severe malnutrition, cooking fuel other thanliquid petroleum gas, inappropriate immunization for age and history of LRTI in the family were thesignificant risk factors associated with ALRTI.

Key words:Breastfeeding, Malnutrition, Passive smoking, Pneumonia.

ACUTE lower respiratory tract infection (ALRTI) is a leading cause of mortality in children below five yearsof age in the developing countries(1). Behrman in a review of epidemiology of ALRTI in developingcountries identified low birth weight, malnutrition, vitamin A deficiency, lack of breastfeeding and passivesmoking as risk factors for ALRTI(2). Recent studies have added other risk factors to the list includingpoor socioeconomic status, large family size, family history of bronchitis, advanced birth order, crowding,young age, air pollution, and the use of non-allopathic treatment in early stages of illness(3-13). Morerecent reviews suggest that indoor air pollution is one of the major risk factor for acute lower respiratorytract infection in children in developing countries(14-15). Many of the factors mentioned are amenable tocorrective measures and may help in reducing the alarmingly high global burden of ALRTI. We, therefore,undertook this study to identify the risk factors for ALRTI in hospitalized children in North India.

Subjects and Methods

The study was carried out from March 1995 to February 1997 in the Pediatric wards of our hospital whichis a tertiary care hospital situated in Northern India. Children admitted with severe acute lower resiratorytract infection (ALRTI) in the absence of under-lying chronic illnesses during the study period wereenrolled in the study as cases.

Acute respiratory tract infection was defined as presence of cough with or without fever for less than twoweeks. Severe ALRTI was defined as presence of lower chest in-drawing with respiratory rates of more


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than 60 per minute in an infant less than 2 months, more than 50 per minute in infants between age group3-12 months and more than 40 per minutes in children between 13-60 months of age(16). Controlsincluded in the study were healthy children below 5 years of age attending Pediatric out-patientdepartment during the study period for immunization.

For both cases and controls, clinical review including history and physical examination, was undertaken to

elicit various potential risk factors and these were recorded in a pre-designed proforma. Age of the childwas recorded in completed months and the age of mother and father were recorded in completed years.Education of mother and father was recorded in completed years of formal education. If a mother orfather of the child were not able to read or write they were labeled as illiterate. For analysis, ages of themother, father and child were converted to categorical variables (mother as 25 years and > 25 years,father 30 years and >30 years, children 1 year and >1 year). History of immunization was elicited fromparents and verified by checking the written document wherever available. A child was assessed to becompletely immunized if he/she had received all vaccinations due for his age according to nationalimmunization schedule(17).

History of smoking by various members in the family and details of cooking fuel used was recorded. Ahistory of upper respiratory infection in mother, father, sibs or grand parents in preceding two weeks anda history of pneumonia/bronchitis in any family member was elicited. Information on the type of house

(thatched or cemented) was recorded.

History of breastfeeding and the age of introduction of supplementary feeding was elicited. Caloric intakeof the child was calculated by recording the food items given to the child regularly prior to the currentillness by recall. Child was examined for pallor and graded as suffering from severe anemia if the color ofpalmer creases was similar to the rest of the palm(18). Length of the child was measured on aninfantometer to the nearest centimeter till the age of two years and thereafter height on a stadiometer.Weight of the child was recorded on beam type of weighing scale to the nearest 100 g. For assessment ofseverity of malnutrition an age independent criteria in form of ratio of weight in kilograms multiplied by 100and length or height in cm2 was calculated. The ratio of more than 0.14 was considered as normal or mildmalnutrition while a ratio of less than or equal to 0.14 was considered as severe malnutrition(19).

Statistical Methods

Data was recorded on a pre-designed proforma and managed on Excel spread sheet. All the entries weredouble checked for any possible key-board error. Association of each of the categorical variable withsevere acute lower respiratory tract infection (outcome variables) was assessed with chi-square test andthe strength of their association was computed by unadjusted odds ratio (95% confidence interval).Variables showing statistically significant association with the outcome variables upto p = 0.2 were consi-dered as potential risk factors of severe acute lower respiratory tract infection. Subse-quently, thesevariables were simultaneously subjected to stepwise multiple logistic regression model to determine thesignificant independent risk factor of severe ALRTI. Data analysis was performed using STATA 6.0Intercooled version (STATA Corp. Houston, Texas, USA). In this study p value less than 0.05 wasconsidered as statistically significant.

Results

In this study majority of children (62.5% in cases and 66.9% in controls) were infants with their agedistribution comparable. There were significantly more boys in cases (73.1%) as compared to controls(64.0%)(p = 0.03). Both mothers and fathers level of education was negatively associated withoccurrence of severe acute lower respiratory tract infection. There were significantly higher numbers ofilliterate mothers (34.8%) in ALRTI group as compared to controls (19.6%) (p


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0.000). Similarly, the families having history of LRTI; and having more than two children at home, weresignificantly positively associated with ALRTi (Table I). Amongst the four nutritional variables consideredin this study, lack of breastfeeding, malnutrition, and inadequate caloric intake were significantlyassociated with ALRTI (Table II). Both the environmental variables (cooking fuel used and type of home)were strongly associated with ALRTI (Table III).

When the variables showing significant association at p 12

76

(37.8)

103

(33.1)

1.0

ex

Male 147 (73.1) 199 (64) 1.51 1.022.24 0.03

Female 54 (26.9) 112 (36.0) 1.0

others age (years)

25 121 (60.2) 143 (46.0) 1.77 1.232.54 0.02

> 25

80

(39.8)

168

(56.0)

1.0

athers age (years)

30 135 (68.2) 193 (62.0) 1.31 0.901.91 0.15

> 30 66 (31.8) 118 (31.8) 1.0

others education

Illiterate 70 (34.8) 61 (19.6) 2.82 1.814.38

10 years 61 (30.4) 78 (25.1) 1.92 1.242.96 0.000

> 10 years 70 (50.8) 172 (55.3) 1.0

athers education

Illiterate

35

(17.4)

19

(6.1)

3.55

1.946.53

10 years 64 (31.8) 95 (30.5) 1.30 0.871.93 0.000

> 10 years

102

(50.8)

197

(63.3)

1.0


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Immunization

Complete for age

60

(29.8)

158

(50.8)

0.41

0.280.59 0.000Incomplete forage

141 (70.2) 153 (49.2) 1.0

URTI

Mother

Yes

36

(17.9)

9

(2.9)

7.32

3.4415.57

0.006

No

165

(82.1)

302

(97.1)

1.0

Father

Yes 3 (1.5) 4 (1.3) 3.18 0.9416.700.062

No 193 (98.5) 307 (98.7) 1.0

Sibs

Yes 39 (19.4) 4 (1.3) 18.47 6.4852.610.000

No 162 (81.6) 307 (98.7) 1.0

Grand Parents

Yes

4

(2.0)

1

(0.03)

6.29

0.6956.720.101

No

197

(98.0)

310

(99.7)

1.0Family history of LRTI

Yes 37 (18.4) 67 (21.5) 2.77 1.884.09 0.000

No 114 (81.6) 244 (78.5) 1.0

No of children at home

>2

78

(39.2)

32

(12.3)

1.78

1.212.61

0.003

2

121

(60.8)

227

(87.7)

1.0

Table II__ Bivariate Relationship Between Various Nutritional variables and Acute Lower RespiratoryTract Infections.

Variables

Acute lower respiratory tract infection

Unadjusted

95% CI

P-value

Yes

(%)

No

(%)

Odds ratio

PallorSevere 29 (14) 11 (21.6) 0.76 0.521.130.186None-mild 172 (86) 40 (79.4) 1.0Breast-feedingNo

55

(27.4)

42

(13.5)

2.08

1.213.590.000 4 mo

99

(39.4)

194

(62.4)

0.814

0.521.26

> 4 mo

47

(33.2)

75

(24.1)

1.0

MalnutritionSevere 115 (59.9) 124 (40.0) 2.24 1.553.230.000Mild/None

77

(40.1)

186

(60)

1.0

Caloric Intake

Inadequate

71

(35.5)

75

(24.8)

1.65

1.112.44

0.011Adequate 130 (64.7) 227 (73.2) 1.0

Table III__ Bivariate Relationship Between Various Environmental variables and Acute Lower RespiratoryTract Infections.

Variables Acute lower respiratory tract infection Unadjusted95% CI p-value

Yes (%) No (%) Odds ratioOther fuelOther than 74 (36.8) 64 (20.6) 2.24 1.513.34 0.006


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LPGLPG

127

(63.2)

247

(79.4)

Type of Home

Thatched 26 (12.9) 15 (4.9) 2.90 1.495.62 0.002

Cemented 175 (87.1) 293(95.1)SmokingMothers

Smoking 1 (0.5) 0 3.11 0.16183.70.33Notsmoking

200 (99.5) 311(100)

Fathers

Smoking

64

(31.8)

85

(27.2)

1.24

0.831.86 0.27Notsmoking

134 (68.2) 226(72.8)

GrandparentsSmoking 1 (0.5) 9 (2.9) 0.18 0.01.31 0.06Notsmoking

187 (99.5) 302(97.1)

LPGLiquid petroleum gas.

Table IV__ Risk Factors of Acute Lower Respiratory Tract Infection Using Stepwise Multivariate LogisticRegression Analysis

Risk factors

Adjusted Odds radio

95% CI

p-value

1.

Cooking fuel other than gas

2.51

1.514.16 0.00002. URTI in mother 6.53 2.7315.610.00003. URTI in siblings 24.07 7.874.4 0.0000

4.No breastfeeding or breastfeeding lessthan 4 months

1.64 1.232.17 0.001

5.

Severe Malnutrition

1.85

1.143.0

0.013

6.

Inappropriate immunization for age

2.85

1.595.0 0.00007. Family history of LRTI 5.15 3.008.82 0.0000

Use of biomass fuels (wood, crop-residues, animal dung), coal and other media (kerosene) arepredominant contributors to indoor air pollution. Nearly half the worlds households, more so in developingcountries and the countryside (90%), use these fuels for cooking. These are burnt in simple stoves withvery incomplete combustion generating a lot of toxic products that adversely affect specific and nonspecific local defenses of the respiratory tract(14,15). The risk is highest for mothers and young childrendue to longer stay indoors and close proximity during cooking. A recent review that systematicallyanalyzed all published studies pertaining to indoor air pollution from biomass fuels concluded that there isa strong consistent increase in ALRTI in young children even after adjusting for confounders such aspoverty. Provision of clean fuels, householders education and modification of stoves are potential

measures to decrease this risk(14,15).

Environmental tobacco smoke (ETS) is another indoor pollutant that reduces local defense mechanismsand predisposes children to invasive infection(20,21). In the present study smoking by the mother, fatheror grand parents did not emerge as a significant risk factor in bivariate analysis. The number of mothersand grandparents who were smokers was low. The number of fathers who smoked was relatively greaterin the cases as compared to controls, but the difference did not reach statistical significance. Theexposure of children due to smoking by fathers may be limited because of relatively greater time spent byfathers outside the home.


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History of LRTI in family was an independent risk factor for severe penumonia. We believe that thisprobably results from family members sharing common environ-ment that predisposed them for LRTI. Thepossibility of asthma/chronic bronchitis in the family members identified as LRTI cannot be ruled out asthe diagnosis was based on the history. History of URTI in the mother or siblings was associated withhigher risk of ALRTI in cases. Most of URTI are caused by viral infections that are highly contagious andlikely to occur in many members of the family. Viral URTI may predispose a child to ALRTI(22).

Lack of exclusive breastfeeding for first four months and severe malnutrition were independent riskfactors for ALRTI. Both these factors can be prevented by proper health education of mothers.Inadequate caloric intake was found to be significant factor associated with ALRTI in bivariate analysisbut it was not a significant factor on multivariate analysis. Caloric intake goes down in all acute illnessestemporarily but longer duration of inadequate intake results in malnutrition. For effect of exclusive breastfeeding on ALRTI, children below 4 months of age were counted with the group of children breastfed forless than 4 months even though they may be exclusively breastfed. To see the true protective effect ofexclusive breast-feeding up to four months we did the entire calculations again after excluding childrenbelow 4 months of age (data not shown). The final results were not altered. It is important to note thatexclusive breastfeeding for first 4 months of life not only protect against severe ALRTI but also protectsfrom development of asthma and other allergic disorders(23,24).

For assessment of malnutrition we used weight/length2 as pediatricians are familiar with it. We alsocalculated weight for height z scores for cases and controls. The result of this analysis also showedmalnutrition as a significant risk factor (OR 2.6; 95% CI 1.25-5.4; p = 0.008) for ALRTI in children below 5years of age.

We observed that children who were immunized for age were less likely to suffer from ALRTI ascompared to those incom-pletely immunized. This was independent of maternal age or education. Itsuggests that mothers utilizing immunization services are better aware of health care facilities andprobably seek early consultation for illness of their children. Awareness of mothers leading to earlyidentification of illness probably avoids severe illness.

We conclude that indoor environmental pollution (use of cooking-fuel other than LPG) and nutritionalfactors (lack of breast-feeding, severe malnutrition) are modifiable major risk factors for severe

pneumonia. Appropriate measures to reduce exposure of children to indoor environmental pollutants likesmokes produced due to use of biomass may help to reduce severe ALRTI. Promotion of exclusivebreastfeeding in first four months and appropriate nutritional supplements thereafter may help indecreasing the incidence of severe ALRTI.

Contributors:SKK was involved in designing the study, collection of data and preparation of manuscript.He will act as a guarantor of the study. SB was involved in design and writing of the manuscript. MG wasinvolved in data collection. RMP was involved in statistical analysis and manuscript writing. RL, TS andRSM helped in drafting the manuscript.

Funding: Department of Biotechnology, Government of India.

Competing interests: None stated.

Key Messages

Lack of breast-feeding, upper respiratory infection in mother, upper respiratory infection insiblings, severe malnutrition, cooking fuel other than liquid petroleum gas, inappropriateimmunization for age, and history of LRTI in the family were the significant contributors ofsevere ALRTI in children under five years.

Sex of the child, age of the parents, education of the parents, number of children at home,anemia inadequate caloric intake, type of housing were not significant risk factors of severe


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ALRTI.


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