Passive smoking at home is a risk factor for community-acquired pneumonia in older adults: a population-based case–control study

Jordi Almirall; Mateu Serra-Prat; Ignasi Bolíbar; Elisabet Palomera; Jordi Roig; Imma Hospital; Eugenia Carandell; Mercè Agustí; Pilar Ayuso; Andreu Estela; Antoni Torres; the Study Group of Community-Acquired Pneumonia in Catalan Countries (PACAP)

doi:10.1136/bmjopen-2014-005133

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Passive smoking at home is a risk factor for community-acquired pneumonia in older adults: a population-based case–control study

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Passive smoking at home is a risk factor for community-acquired pneumonia in older adults: a population-based case-control study
Jordi Almirall
Published on: 23 November 2015
Issues before interpretation foo making informed decision making
Pankaj B Shah
Published on: 23 November 2015

Published on: 23 November 2015
Passive smoking at home is a risk factor for community-acquired pneumonia in older adults: a population-based case-control study
- Jordi Almirall
- Other Contributors:
  Mateu Serra-Prat, Ignasi Bolibar et al.
Dear Prof Pankaj B Shah, Thank you very much for your comments and for the opportunity to clarify the design, the data and the results of the present analysis. The PACAP study was a large population-based case-control study that recruited 1336 cases of CAP and 1326 controls without CAP matched by age and sex (total sample of 2662 subjects). For the purpose of assessing the effect of passive smoking on CAP, only never smo...
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Dear Prof Pankaj B Shah, Thank you very much for your comments and for the opportunity to clarify the design, the data and the results of the present analysis. The PACAP study was a large population-based case-control study that recruited 1336 cases of CAP and 1326 controls without CAP matched by age and sex (total sample of 2662 subjects). For the purpose of assessing the effect of passive smoking on CAP, only never smokers were selected from the original PACAP sample. Among this original sample, 1003 subjects were never smokers and constitute the subsample for the present analysis. Never smokers were then classified as passive or non-passive smokers at home depending if they reported to be exposed to tobacco consumption at home or not. We hereby present the results for all age groups: 1.- Never smoker(>14 years group) Passive smokers at home:CAP 143;Controls(without CAP) 140 Non-Passive smokers at home: CAP 328; Controls (without CAP) 392 TOTAL: CAP 471; Controls(without CAP) 532
Data from the subgroup of subjects >65 years of age were as follows:
2.- Never smokers(>65 years group) Passive smokers at home:CAP 59;Controls(without CAP)43 Non-Passive smokers at home: CAP 168; Controls (without CAP) 195 TOTAL: CAP 227; Controls(without CAP) 238
On the other hand, as mentioned in the data analysis section in the manuscript two approaches were established to assess the relationship between passive smoking and CAP: a) estimation of incidence of CAP in general >14 years population (for exposed and non-exposed) and the RR, from the prospective phase of the study and b) estimation of OR from the case-control study. In our opinion, presenting the results of both different analyses is of value because both showed very similar and concordant results which reinforce their robustness. Controls were frequency matched by age and sex with cases in the original PACAP sample. However, when selecting only the subgroup of never smokers this matching could be lost. That is beacuse we also present results adjusted for age and sex. Finally, regarding the effect of passive smoking in ?65 years old subjects, with a statistically significant chi square, crude OR (1.59) and RR (1.48) and with and adjusted OR (1.56) just in the limit of significance, we conclude that passive smoking is a risk factor for CAP in this age group.
Conflict of Interest:
None declared
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Conflict of Interest:
None declared.
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Published on: 23 November 2015
Issues before interpretation foo making informed decision making
- Pankaj B Shah, Professor
Dear Sir, at the outset, I would like to congratulate BMJ open and authors for publishing wonderful study. There are certain issues which needs more clarity before an reader can make informed decision. 471 patient mentioned in abstract is missing in the content of the paper. The number of cases and control somehow do not match with the earlier paper cited for the detailed methodology. After preparing 2X2 table, authors...
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Dear Sir, at the outset, I would like to congratulate BMJ open and authors for publishing wonderful study. There are certain issues which needs more clarity before an reader can make informed decision. 471 patient mentioned in abstract is missing in the content of the paper. The number of cases and control somehow do not match with the earlier paper cited for the detailed methodology. After preparing 2X2 table, authors should have restricted to either calculation of OR or RR rather than both as the results make interpretations difficult. The authors indicate about frequency matching for age, sex while same is adjusted in logistic regression. It is also indicated that controls are selected from the random sample which is probably difficult as only 1003 participants were never smokers which includes 471 cases. This number 1003 also does not match which the earlier study cited for detail methodology. Passive smoking definition is restricted to only current smokers. CAP can have some risk associated with people living earlier with a smoker but not currently staying. Some of the results are included in data analysis section which could have been avoided. It is indicated that table shows significant result for participants more than age 65 years but adjusted odds ratio is 1.56 (1.00 to 2.45. Since CI has 1 that indicates that there is no significant association. Comparing the same with RR in table 2, it is 1.48 (1.08 to 2.03)which indicates significance. Hence it may be good on authors part to restrict to either OR or RR. If authors believe that this is case control study, then they should have restricted to OR.If the author assumes that since it is population based case control study which can assess incidence and relative risk, they should have avoided OR. If authors believe that this is case control study, then they should have restricted to OR.
All these issues are very important for making informed decision.
Conflict of Interest:
None declared
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Conflict of Interest:
None declared.
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