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We appreciate the comments of Macleod and Davey-Smith on our recent
article reporting an association between systemic inflammation markers and
socio-economic status.[1,2] In their letter, Macleod and Davey-Smith
state that our findings, particularly the association of fibrinogen with
socio-economic status, and its interpretation is not correct, and runs
contrary to the principle of "Mendelian randomisat...
We appreciate the comments of Macleod and Davey-Smith on our recent
article reporting an association between systemic inflammation markers and
socio-economic status.[1,2] In their letter, Macleod and Davey-Smith
state that our findings, particularly the association of fibrinogen with
socio-economic status, and its interpretation is not correct, and runs
contrary to the principle of "Mendelian randomisation". As the evidence,
they refer to the finding that plasma fibrinogen concentrations are
related to a polymorphism in the b-fibrinogen gene, with presence of the
"T" allele being associated with higher levels. According to the authors,
this finding is in keeping with the evidence from controlled trials which
suggests that drugs lowering fibrinogen do not decrease the risk of
coronary heart disease (CHD) and therefore, the association between plasma
fibrinogen and CHD risk is most probably not causal.
We believe, however, that the authors have misinterpreted our
findings and conclusions to some extent. First, we did not study the
relationship of fibrinogen to the risk of cardiovascular disease, but our
aim was merely to study the association of systemic inflammation markers
and socio-economic status in a cross-sectional design. The relationship of
plasma fibrinogen level and CHD risk has been found in a number of
prospective observational studies. Data on clinical trials are scarce, and
do not in our understanding justify any conclusions about the causality on
the observed association at the moment.[2]
Furthermore, we did not state that the fibrinogen-social position
link is not a reflection of the social patterning of prevalent disease, or
other health related behavioural or biological factors (smoking, obesity
etc.). In our article, we said that systemic inflammation is a biologically
plausible mediator between socio-economic status and the risk of
cardiovascular disease but our intention was not to state that socio-
economic position as such causes chronic systemic inflammation. Therefore,
we concluded also that other factors, which were not included in the
analyses, such as prevalent or sub-clinical diseases, and behavioural and
environmental factors, such as diet, exercise and exposure to toxic
substances at work or elsewhere, and low birth weight may be involved.
We suspect also that the concept of "Mendelian Randomisation", if
used the way the authors are using it, is not going to be very helpful for
untangling the causal roles of factors that lead to the disease outcomes.
They take one single nucleotide polymorphism (SNP) of a single gene, in
this case the fibrinogen beta gene, and draw inferences from that to the
plasma fibrinogen concentration and to the causal effects of fibrinogen on
the coronary heart disease risk. This is a simplistic view, which does not
take properly into account the complex genetic background of a
multifactorial disease. Usually, the repeatability of these single gene -
single SNP studies has been poor. As to fibrinogen, there are three genes
encoding the fibrinogen molecule, fibrinogen alpha, fibrinogen beta, and
fibrinogen gamma. At least 157 SNPs are known in these three genes.[4,5]
Furthermore, other genes, such as the IL-6 gene, are likely to have an
effect on the fibrinogen concentration. There is enormous potential for
interactions between these different genetic variants as well as between
the genetic variants and 'environmental' factors. In addition,
pleiotropism and epistasis are common. Therefore, we think that the
concept of "Mendelian randomisation" is, in most cases, a cross
oversimplification of the underlying biology of a complex, multifactorial
disease. We suspect that its applicability is likely to be rare and
limited to few special occasions.
References
1. Macleod J, Davey Smith G. Fibrinogen, social position, and risk of
heart disease. J Epidemiol Community Health 2004;58:157.
2. Jousilahti P, Salomaa V, Rasi V, Vahtera E, Palosuo T. Association of
markers of systemic inflammation, C reactive protein, serum amyloid A, and
fibrinogen with socio-economic status. J Epidemiol Community Health
2003;57:730-733.
3. Danesh J, Collins R, Appleby P, Peto R. Associaitons of fibrinogen, c-
reactive protein, albumin or white cell count: meta-analyses of
prospective studies of coronary heart disease. JAMA 1998;279:1477-1482.
4. Sing CF, Stengard JH, Kardia LR. Genes, environment, and cardiovascular
disease. Arterioscler Thromb Vasc Biol 2003;23:1190-6.
My understanding, confirmed by brief review of data on the ONS
website, is that the South Asian population in the UK has a younger age
distribution than the white population. In this case, would an indicator
based on those aged over 35 need further adjustment for the age
distribution beyond 35 in order to examine prescribing? Is it possible
that we are seeing an age effect in the negative correlation...
My understanding, confirmed by brief review of data on the ONS
website, is that the South Asian population in the UK has a younger age
distribution than the white population. In this case, would an indicator
based on those aged over 35 need further adjustment for the age
distribution beyond 35 in order to examine prescribing? Is it possible
that we are seeing an age effect in the negative correlation of
prescribing rates and ethnic minority population proportions?
Conflict of Interest
YHEC Ltd is a contract research company and
carries out projects for both the NHS/DH and for the pharmaceutical
industry. We are not conducting any current research on prescribing rates
for coronary heart disease nor do we see the paper or our comment as
impinging on any of our current work.
We read with great interest the recent paper by Martins et al.[1]
concerning the influence of socioeconomic conditions on air pollution
adverse health effects in elderly people in Sao Paulo, Brazil. These
results are very interesting and may promote understandings of which
social category of persons are most sensitive to air pollution. The
authors suggest that socioeconomic deprivation represents a...
We read with great interest the recent paper by Martins et al.[1]
concerning the influence of socioeconomic conditions on air pollution
adverse health effects in elderly people in Sao Paulo, Brazil. These
results are very interesting and may promote understandings of which
social category of persons are most sensitive to air pollution. The
authors suggest that socioeconomic deprivation represents an effect
modifier of the association between air pollution and respiratory deaths
in elderly people for an increase of 10 µg/m3. They conclude that poverty
represents an important risk factor that should be taken into account when
determining the health consequences of environmental contamination. We
agree with these conclusions nevertheless, the question is to know if poor
people died because they are more illness or inaccessibility (geographic
and economic considerations) to health care system or because they were
more exposed to air pollution ?
We know that people with lower socioeconomic status are more sensitive to
a large number of risk factors according to different life habits, or to
addictive conducts as smoking habits [2].
When air pollution is considered, socioeconomic characteristics as an
effect modifier can take two aspects. First, people with low socioeconomic
status may be more sensitive in term of health effect because they have
associated pathologies and individuals with certain diseases had a greater
risk of dying during an episode of increased of air pollution than did
members of the general population [3]. Furthermore, people living in
underprivileged sectors would have both more limited access to healthcare
[4] and greater exposure to air pollution. Exposure conditions is the second
aspect of the interpretation of the effect modifier. Jerrett et al.[5]
argue, low socioeconomic conditions may be associated with manufacturing
and so with a higher workplace exposures, but also with a lower mobility.
In addition, persons with lower socioeconomic characteristics may be
exposed to a complex mix of pollution from indoor sources, as well as
outdoor pollution due to traffic, industry, and waste burning in
developing countries. It seems necessary to explore the link between
individual exposure and socioeconomic characteristics because these two
factors are strongly correlated.
More studies are need to investigate this effect modifier and particularly
the signification of this effect. To understand this effect we will need
individual data on risk factor but also data on individual exposure to
have a good interpretation of the results and to have policy implications.
References
(1) Martins MC, Fatigati FL, Vespoli TC et al. Influence of socioeconomic
conditions on air pollution adverse health effects in elderly people: an
analysis of six regions in Sao Paulo, Brazil. J Epidemiol Community Health
2004;58:41-6.
(2) Prescott E, Godtfredsen N, Vestbo J, Osler M. Social position and
mortality from respiratory diseases in males and females. Eur Resp J
2003;21:821-6.
(3) Goldberg MS, Burnett RT, Bailar JC et al. Identification of persons
with cardiorespiratory conditions who are at risks of dying from the acute
effects of ambient air particles. Environ Health Perspect 2001;109:487-94.
(4) Chen Y, Dales R, Krewski D. Asthma and the risk of hospitalization in
Canada : the role of socioeconomic and demographic factors. Chest
2001;119:708-13.
(5) Jerrett M, Burnett RT, Brook J et al. Do socioeconomic characteristics
modify the short term association between air pollution and mortality ?
Evidence from a zonal time series in Hamilton , Canada. J Epidemiol
Community Health 2004;58:31-40.
It is important to highlight shortfalls in service delivery to looked after children. However, the provision of information as in the quoted study is seldom enough to change practice.
In Northern Ireland we have had integrated health and social services
since the early 1970s. As part of Children's Services Planning we tagged
the records of Looked After Children and compared the immunisation stat...
It is important to highlight shortfalls in service delivery to looked after children. However, the provision of information as in the quoted study is seldom enough to change practice.
In Northern Ireland we have had integrated health and social services
since the early 1970s. As part of Children's Services Planning we tagged
the records of Looked After Children and compared the immunisation status
of Looked After Children (LAC) and children who were not Looked after.
The results are shown here in Table 1.
Table 1 Child health system records of looked after and other children in
Craigavon Banbridge Health and Social Services Trust, October 2001.
Number (%) of children
born 1 Jan 1987 to 31 Dec 1999
Looked after
children (n=75)
Other children
(n=23 936)
Completed Primary
immunisations
67 (89.3)
22979 (96)
Meningococcal C
68 (90.6)
22260 (93)
Measles, mumps, and rubella
69 (92)
22979 (96)
These figures have been published.[1] Integrated health and social
services can be an effective means of protecting the health of vulnerable
children in Society.
Reference
1. Farrell B., Findings for looked after children are not
generalisable. BMJ 2003; 326:1088 (letter)(17 May)
The paper by Syed et al,[1] provides observations on the use of face
masks by members of the public for protection against the severe acute
respiratory syndrome (SARS) coronavirus (CoV).
The authors’ raise an
important question as to whether masks are effective in preventing
disease. The type of masks used can generally be categorized as either
surgical or paper and are suggested to off...
The paper by Syed et al,[1] provides observations on the use of face
masks by members of the public for protection against the severe acute
respiratory syndrome (SARS) coronavirus (CoV).
The authors’ raise an
important question as to whether masks are effective in preventing
disease. The type of masks used can generally be categorized as either
surgical or paper and are suggested to offer similar protection. For
health care workers (HCW), it has been shown [2] that masks do not provide
adequate protection against SARS CoV. However, protection for HCW is
somewhat different than that for those of the general public, especially
those not directly exposed to droplet transmission on a “continous” basis
from an infected individual. The finding of a possible dose-response [3] for
exposure and infection to SARS CoV lessens the chance of infection through
droplet transmission by the general public, especially when some personal
protection is afforded. When masks are used along with other hygiene
practices, risk of infection, excluding close contact with an infected
person, like a family member, can be minimized.
Masks have been shown to provide an increased protection rate of 2.[4]
for Mycobacterium tuberculosis in comparison to no mask4. Since SARS CoV
has been suggested to be spread by aerosol droplet and not to any
significant degree by airborne transmission,[5] masks will probably provide
some increased protection to the general public. However, as noted by
Syed, it is necessary that they be properly used and changed frequently.
Since this virus can survive for 72 hours or more on surfaces, its
transmitted through fomite contact and infection can occur by mucus
membranes (e.g. conjunctiva);[5] thus, other personal hygiene practices
(e.g. hand washing) are of equal or greater importance4.
For public health protection, use of masks can have some impact on
preventing the spread of SARS CoV. However, this should be only one
health practice that is encouraged by the public since others (e.g. hand
washing) are also of great importance.
References
1. Syed Q, Sopwith W, M Regan M, Bellis MA. Behind the mask. Journey
through an epidemic: some observations of contrasting public health
responses to SARS. J Epidemiol Community Health, 2003; 57: 855 - 856.
2. Lange JH. SARS and respiratory protection. Hong Kong Medical
Journal 2004; 10: 392-3.
3. Scales DC, Green K, Chan AK, Poutanen SM, Foster D, Nowak K,
Raboud JM, Saskin R, Lapinsky SE, Stewart TE. Illness in intensive-care
staff after brief exposure to severe acute respiratory syndrome. Emerg
Infect Dis [9: 1205-10] 2003 Oct [accessed December 19, 2003]. Available
from: http://www.cdc.gov/ncidod/EID/vol9no10/03-03-0525.htm
4. Barnhart S, Sheppard L, Beaudet N, Stover B, Balmes J.
Tuberculosis in health care settings and the estimated benefits of
engineering controls and respiratory protection. J Occup Environ Med 1997;
39: 849-853.
5. Centers for Disease Control and Prevention. Public health guidance
for community-level preparedness and response to Severe Acute respiratory
Syndrome (SARS). Draft, October, 2003;
http://www.cdc.gov/ncidod/sars/sarsprepplan.htm
Dear Editor
We appreciate the comments of Macleod and Davey-Smith on our recent article reporting an association between systemic inflammation markers and socio-economic status.[1,2] In their letter, Macleod and Davey-Smith state that our findings, particularly the association of fibrinogen with socio-economic status, and its interpretation is not correct, and runs contrary to the principle of "Mendelian randomisat...
Dear Editor
My understanding, confirmed by brief review of data on the ONS website, is that the South Asian population in the UK has a younger age distribution than the white population. In this case, would an indicator based on those aged over 35 need further adjustment for the age distribution beyond 35 in order to examine prescribing? Is it possible that we are seeing an age effect in the negative correlation...
Dear Editor,
We read with great interest the recent paper by Martins et al.[1] concerning the influence of socioeconomic conditions on air pollution adverse health effects in elderly people in Sao Paulo, Brazil. These results are very interesting and may promote understandings of which social category of persons are most sensitive to air pollution. The authors suggest that socioeconomic deprivation represents a...
Dear Editor
It is important to highlight shortfalls in service delivery to looked after children. However, the provision of information as in the quoted study is seldom enough to change practice.
In Northern Ireland we have had integrated health and social services since the early 1970s. As part of Children's Services Planning we tagged the records of Looked After Children and compared the immunisation stat...
Dear Editor
The paper by Syed et al,[1] provides observations on the use of face masks by members of the public for protection against the severe acute respiratory syndrome (SARS) coronavirus (CoV).
The authors’ raise an important question as to whether masks are effective in preventing disease. The type of masks used can generally be categorized as either surgical or paper and are suggested to off...
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