Importance of Incidence Rate Ratio in Public Health Study

This study explains the importance of incidence rate ratio in public health and how it measures the frequency of a given incidence over a specific time period. It also discusses the type of study, study design characteristics, and the estimation of attributable risk.

Running head: PUBLIC HEALTH 1
Public health
Students name:
Instructors name:
Course name:
Date:

PUBLIC HEALTH 2
Public health
Attributable risk involves the variation of new cases in exposed and non exposed
individuals. The risks involved measures the possibility of an illness in exposed set of people
attributable to the exposure. On the contrary, this is done by eliminating a risk that would have
happened as a result of other causes. However, they may determine the number of disease cases
in the exposed group that could be avoided if the exposure factors were removed.
An odd ratio that is more than one shows an increase in the occurrence of a given event.
On the other hand, a possible ratio that is less than one indicates a reduction in the event that is
about to occur. Relative risk also known as risk ratio involves the ratio in possibility of disease in
an exposed group to the probability of the same illness individuals not exposed to it. Relative
risk measures relationship between exposure and the disease outcome basing on the incidence of
the illness in the group that is exposed in relation to those not exposed.
Relative risk is equal to one that may show there is no association between a given
exposure and the outcome. In addition, the one that may be greater than one indicates a positive
association to mean that there is increased risk of a disease when exposed to a given factor. The
risk that may be less than one explains a reduction in risk of a disease outcome as a result of
exposure to a certain factor. Incidence rate explains new cases of an illness that is within a
specified period of time (Bayne, Farah, Herbst & Hsieh 2018). However as a part of the
population at danger in disease it measures frequency in which disease arises over a given
specific period of time. Only new cases are captured during calculations while the initial ones are
excluded.
Case-control studies are retrospective study designs which define two groups, one
having disease and that without disease. It examines whether there is a reasonable difference in
the rates of exposure to a specific risk factor between the groups. This study involves cases and
controls whereby cases involve patients having the disease while controls are patients who do not
have the disease.

PUBLIC HEALTH 3
(1a) Importance of the incidence rate ratio in this study
The incidence rate ratio is important in this study since it measures the frequency in which a
given incidence occurs over a specific time period. In the study, it provides information on the
number of new cases of bladder cancer in Northern Italy and gives a picture of changes in
bladder cancer disease progression. Incidence rate must be calculated in order to determine
attributable risk that base on the exposures factors like cigarettes smoking, coffee consumption,
history of cystitis, occupation at risk and vegetable consumption.
(b)Type of study
A retrospective case-control design was used in the study since it examines exposures to
blood cancer risk on protective factors in relation to their outcome. It uses existing data like
medical records, administrative database, and interviews with patients known to have the disease
to compare cases and controls. The group of people who have developed blood cancer is
compared to those without illness and hypothesis is formulated concerning a possible association
between blood cancer and exposure factor for further investigation on potential relationship
between the factors and the disease.
(c) Study design characteristic used in the estimation of the incidence rate ratio
The main characteristic in the study is time since the populations in the study have to be
monitored for a specific period of time to identify whether they may be infected by bladder
cancer on exposure to the given factors.
(2) A similarity in the distribution of variables in cases and control
The used variables in table 1 are sex, age, and education on the factors resulting in bladder
cancer (Abnet, Arnold & Wei 2018). These variables are same for those having disease and those
without the illness in order to find whether there is possibility of new cases from those with and
without the disease in relation to the risk factors.
3(a)
Relative risk is the estimated parameter in table 3 and 4 since it is calculated as the
possibility of an illness in a group that is exposed to that of not exposed group.

PUBLIC HEALTH 4
(b) Formula in calculating Relative risk
(i) Cohort study context: it is expressed as the incidence of a disease in the exposed group to
that of the unexposed group.
Relative risk = Incidence in exposed/ incidence in unexposed
RR=Ie/Iu
( ii) case-control study context: it is calculated as the probability of disease in cases to that of
disease in controls.
Disease No
disease
Cases a b
Controls
c d
Probability of disease in cases, R1 = a/(a+b)
Probability of disease in controls, R2= c/(c+b)
Therefore Relative Risk= threat of occasion in treatment group/ threat of occasion in control
group.
=a/(a+b)/ c/(c+b)
4 Attributable risk estimation
Event No event
Yes a = 68 b = 25
No c = 363 d = 466
Odd Ratio (OR) =ad/bc
=68 x 466/363 x 25
OD = 3.49
Estimation of population exposure (Px) = c/c + d
= 363/(363 +466)
Px = 0.44

PUBLIC HEALTH 5
Percentage of attributable risk = Px x (OR-1)/ 1+ Px (OR -1) x 100%
0.44 ( 3.49 – 1)/1 + (0.44 x 3.49-1) x 100%
Attributable risk percentage = 52.28%
(b) Comparison of the attributable risks
The estimated attributable risk value in history of cystitis is higher than that in Table 3.
This shows that cystitis history can highly contribute to bladder cancer. In reduced cystitis cases
attributable risks for bladder cancer is decreased as in Table 3.
Conclusion
Cohort and case control studies are important since they are done to find out whether given
factors increase the likelihood of a disease in a given group of people. This study helps in
avoiding false hypotheses on disease causes that have not been proved. It also helps in providing
information on how to prevent various illnesses in populations by minimizing the risk factors
that increase probability of a disease. When a study has established that various factors increase
the possibility of an illness, measures can be put in place to ensure that these factors are
eliminated to control populations from acquiring the disease. Health education can be done to
educate people on the dangers that can result to a given illness.

PUBLIC HEALTH 6
References
Abnet, C. C., Arnold, M., & Wei, W. Q. (2018). Epidemiology of esophageal squamous cell
carcinoma. Gastroenterology, 154(2), 360-373.
Bayne, C. E., Farah, D., Herbst, K. W., & Hsieh, M. H. (2018). Role of urinary tract infection
in bladder cancer: a systematic review and meta-analysis. World journal of urology, 36(8), 1181-
1190.