Oct 1, 1988 - oa South African Medical Journal - Crowding and alcohol abuse as risk factors for tuberculosis in the Mamre population - results of a ...
352
SAMT VOL 74
1 OKT 1988
Crowding and alcohol abuse as risk factors for tuberculosis in the Mamre population Results of a case-control study N. COETZEE,
D. YACH,
G. JOUBERT
Summary As part of a community health programme, a populationbased case-control study was undertaken to determine whether crowding and alcohol are risk factors for tuberculosis in Mamre. Forty notified cases of tuberculosis were compared with 84 randomly selected controls. Cases and controls were group-matched for age and sex. Seventy-six per cent of dwellings had a housing density ratio greater than 100%. There was no association between crowding and tuberculosis, but cases lived in houses that were significantly older than those of controls (odds ratio 4,8, 95% confidence interval 1,5 - 15,6). There was an association between alcohol problems in the household and tuberculosis (odds ratio adjusted for employment status 2,2, 95% confidence interval 1,3 - 3,8). Further studies using refined methods are needed to evaluate the role of crowding in tuberculosis. The need for alcohol intervention campaigns in conjunction with tuberculosis control programmes directed at high-risk groups should be considered. S Air Med J 1988: 74: 352-354.
Tuberculosis is the leading notifiable disease in the RSA1 and accounts for considerable morbidity2 and monality.3 The notification rate in the coloured population has been increasing since the mid-1970s. 4 The notification rate for tuberculosis in Mamre in 1986 was 5,6/1000, similar to the tuberculosis incidence rate in the western Cape. 5 Pulmonary tuberculosis is a disease with low infectiousness.6, 7 Close and prolonged contact (such as sharing a household) is known to increase the secondary attack rates of contacts. 8- 11 Several explanations for the high incidence of tuberculosis among coloureds have been suggested. These include overcrowding as a risk factor for infection, alcohol and smoking as risk factors for disease,l2-15 and patient and health service compliance. 16 Crowded living conditions have been documented as being associated with an increased occurrence of several diseases, tuberculosis in particular. 17-19 Various studies have attempted to quantify the degree of association between tuberculosis infection and crowding. 20- 22 They have encountered several methodological problems. These include defining crowding adequately,23 differentiating crowding in a house from residential density, (the latter refers to the proximity of dwellings to each other regardless of the density of occupation per house 24 ), adjustment for factors that could confound the tuberculosis-crowding relationship of
Department of Community Health, University of Cape Town N. COETZEE, M.B. CH.B., D.A. (S.A.), D.T.M. & H. Centre for Epidemiological Research in Southern Africa, South African Medical Research Council, Parowvallei, CP D. YACH,
indices of crowding,24-26 lack of temporality, ecological fallacyp and failure to distinguish between disease and infection. Alcoholism and alcohol intake are also closely associated with tuberculosis disease 1H5 and one hospital-based study found a 49% prevalence of.alcoholism in patients with newly diagnosed tuberculosis. 14 The rate for active tuberculosis among indigent alcoholics and drug abusers is 28 times that of the general New York City population. 13 The purpose of this study was to determine whether crowding and alcohol problems in the household were risk factors for tuberculosis in a defined community.
Methods A census of the population of Mainre28 that included healthrelated information was conducted in November/December 1986. A case-control study was designed using the 1986 census data as baseline information. Cases were defined as all Mamre residents (in 1986) notified for tuberculosis (pulmonary and other) to the Cape Divisional Council during 1984 to 1986 47 cases met this definition. Potential controls included all residents who were reponed in the census data set as not having been treated for tuberculosis in 1986, had not been notified for tuberculosis to the Cape Divisional Council since 1977, and did not share a household with the cases. Ninety-four controls were selected by means of random number generation and group-matched for age and sex to cases. Two field-workers, blinded to the case/control status of subjects, visited the dwellings of cases and controls in November/December 1987, administered the pretested questionnaires and toojl: measurements of the dimensions of all sleeping rooms (including floor surface area, ceiling height and openable window surface area). The questionnaire obtained information about the relationship of the respondent to the study subject, duration of stay in the dwelling, renovations and additions to the house, and history of tuberculosis treatment. Information concerning alcohol consumption was obtained from the 1986 census data set. A household with an alcohol problem was defined as a household in which one of its members reponed alcohol to be a problem. The reliability of measurements was determined by repeating all sleeping room measurements on 11 randomly selected dwellings. . Analysis. Indices of crowding and cut-off points are specified in the Appendix. Cases were compared with controls and odds ratios 29 (with 95% confidence intervals) for risk factors were calculated as the measure of association.
Results
M.B. CH.B., B.sc. HONS (EPIDEMIOL.), M.P.H.
G. JOUBERT,
B.A., B.Sc. HONS
Cases and controls did not differ with respect to their response rate or age and sex distribution (Table I). One control had to
SAMJ
TABLE I. DISTRIBUTION OF SELECTED VARIABLES IN CASES AND CONTROLS Responded to survey Sex Male Female Total Age (yrs) 0,05) (Table I). However, cases lived in dwellings that were signiftcantly older than those of controls (Table 11). Cases did not differ from controls in respect of other indices of crowding used (Table 11). An association was found between households that reponed alcohol to be a problem and tuberculosis (odds ratio 3,97, 95% conftdence interval 1,51 - 10,54). The association remained after adjustment for employment status (adjusted odds ratio 2,2, 95% conftdence interval 1,3 - 3,8).
Discussion
= 4,67 (P = 0,03).
be excluded because she had been cenified as having had tuberculosis. For the analysis double cases and controls were excluded so as to prevent any possible effect of clustering of risk factors in the household. The fmal analyses were therefore conducted using 35 cases and 80 controls. The reliability of sleeping room measurements (assessed by calculating the median difference between the fust and second measurements, expressed as a percentage of the median measurement of the ftrst reading) was 5,8% for room volume
The housing characteristics of cases and controls are similar. The significant difference in age of dwellings between cases and controls is probably linked to social and economic factors, since poorer families reside in older hpmes. The sleeping rooms of 34% of dwellings did not comply with the National Building Regulations and Building Standards Act No. 103 of 1977 specifications for natural ventilation (minimum openable window area per room should be at least 5% of the total floor area, or 0,2m2 , depending on which is greater). According to the specifications of the Slums Act the minimum sleeping room volume per person of 29% of households is inadequate. The minimum speciftcation for sleeping room floor area per person (Slums Act No. 76 of 1979) was not met in 26% of households. Of concern is the high percentage of dwellings (76%) that have a housing density ratio greater than 100%. It is interesting
TABLE 11. AGE OF DWELLING AND INDICES OF CROWDING* Age of dwelling (years)t >80 2,5 was considered to be an indicator of crowding. 4. EPs per habitable room in dwelling (EPPH). A value of> 2,5 was considered to be an indicator of crowding. EP values rather than true counts were used so as to gain better perspective on the amount of space occupied per person. Children aged under 10 years would need less space and could share sleeping rooms with adult couples.
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