INTRODUCTION for determining occurrence and natural history of


essay reviews three peer-reviewed and published scientific academic journal articles
(Mahishale et al 2015; Schett et al 2013; Penn et al 2013). The essay
discusses the advantages and disadvantages of cross-sectional study, cohort
study and randomised control trial studies. A brief discussion of the case-control
studies will be given. The essay will also give a definition of what
epidemiology is and why it is important and its value in public health activities.
The essay will conclude by summarising all key issues mentioned in the essay.

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is defined as “the study of how often diseases
occur in different groups of people and why” (Thacker 2006). A range of methods can be used to perform
epidemiology investigations; surveillance and descriptive research studies which
can be used to study distribution; analytical studies can also be used to study
determinants (Thacker 2006). The importance of epidemiology is that it saves money during the course of prevention. The
investigation would recognize the reason of the outbreak and show the way to
interventions to prevent more cases of the disease happening.

studies trail a group of individuals to determine if the developments of the
out of interest are different between groups with different exposures to jeopardy
factors. The advantages of cohort studies are that they are the best method for
determining occurrence and natural history of ailment. They avoid moral troubles
of experimental exposure to jeopardy factors (Concato and Horwitz 2004).
Multiple results variables can be measured in a single study. The disadvantages
are that they are more costly to put in place and maintain; loss of trail up
put at risk the validity of outcomes, ineffective studying outcomes that are uncommon
or have an extended latent period, accounting for confounding issues and they
are more subject to bias than Randomised control trials (RCTs)? (Concato and
Horwitz 2004).

Control Trials gives the most excellent estimated of the beneficial effects of
treatment. Their advantages are that they are the most excellent process for
evaluating effectiveness, randomisation avoids confounding, and Bias is reduced
by allocation concealment and blinding. Their disadvantages are that they are hard;
they take more time and are very expensive. They have moral restrictions, strict
exclusion/inclusion criterion and volunteer bias lessens generalisability, restricted
trail up necessitates surrogate end points and ineffective for investigating uncommon
adverse effect (Gluud 2006).

studies are studies in which groups of individuals of diverse types are collected
and put into one large sample size group and studied at only a single point
(Kunz et al 2007). The advantages of these studies are that they are not costly
to perform and does not need a lot of time; they are used to show/or disprove
assumptions; captures an exact point in time; includes multiple variables at
the time of statistics collection; the information can be used for different
types of research studies and many findings and results can be analysed to generate
new theories/studies or in-depth research studies. The disadvantages of these
studies are that they cannot be used to investigate behaviour over a period of
time; does not assist in determining the cause and effect; the timing of the data
collections is not certain to be representative and results can be faulty or twisted
if there is a disagreement of interest with the financial support (Kunz et al

control studies are generally retrospective, applicants with the outcome of
interest are matched alongside applicants from the source population who do not
have the outcome variable (Schultz et al 2002). The advantages of these studies
are that they are good quality for uncommon diseases or outcomes with a long
duration between exposure and results and the disadvantage is that confounding
factors are hard to control (Schultz et al 2002).

Cross-sectional study

et al 2015 undertook a cross-sectional study research to determine the
relationship between Chronic Obstructive Lung diseases (COPD) and the common,
chronic comorbid conditions of diabetes mellitus (DM), hypertension (HTN) and
cardio-vascular diseases (CVD) and also to determine how these affect the
clinical course of COPD. A cross sectional study was performed whereby all the
COPD groups diagnosed as per Global Initiative for Chronic Obstructive Lung
disease-2013 (GOLD 2013) criterion were screened for DM, HTN and CVD as per
national and World Health Organization (WHO) guidelines.

sources of the information was extracted from inpatient and outpatient
departments of pulmonary medicine, Internal medicine and endocrinology and
cardiology department at a tertiary care hospital at Belgaum district of Karnataka
in India. The prime information was gathered between January 2013 and December
2014. The inclusion criterion included both male and female patients diagnosed
with COPD and were aged 40 years and above. The exclusion criteria was when
patients had any chronic lung disease previous than COPD, connective tissue
disorders, HIV infection, chronic liver disease, chronic renal failure, chronic
alcoholics and  malignancies on long-term
steroid or cytotoxic drug therapy.

information which was recorded integrated biomass fuel exposure, age, sex, symptoms
related to the respiratory system, HTN, DM and CVD with length of illness level
of dyspnoea, smoking status, previous medication, current treatment, occupation
and number of exacerbations that is the number of emergency hospital admissions
on unplanned hospital visits in the past. All applicants were subjected to
spirometry and patients with history of bronchodilator predicted were measured
as cases of COPD. After that they were branded as mild, moderate, severe and
very severe COPD patients as per the GOLD guidelines.

All applicants
were assessed by a consensus panel that decided after plenary conversation
whether diagnosis of HTN, CVD or DM was presented, likely or not present. The
panel comprise of general physicians, pulmonologist, and cardiologist.
Diagnosis of COPD was established as per the strategies of the GOLD program,
which gives standard diagnostic criterion, severity staging as well as commendations
for deterrence and managing of COPD. The panel established diagnosis of HTN, CVD
and DM if participants met the WHO criterion for these disorders.

thousand four hundred and thirty-two applicants with COPD were recruited in the
research study with one thousand six hundred and forty-eight males and seven
hundred and eight-four females. About one thousand three hundred and fifty-one
applicants were smokers whilst six hundred and fifty-three had a past history
of biomass fuel exposure. Analyses demonstrated that increasing age, a higher
pack year of smoking, high dose score and male sex were linked with a higher
risk of HTN CVD and DM. NCDs as well as COPD, HTN, DM and CVD are the main worldwide
health problems. They are the global leading cause of disease burden and death
and are increasing in occurrence even in low and middle income countries like

presents of numerous co-morbidities adds to the complications and heterogeneity
of COPD. The worldwide aging of the world’s population is reinforcing this
trend, partially due to the fact that the occurrence is higher in age groups.
The current research study showed that the occurrence of DM in study groups was
25.94% which is substantial higher than the national average of eight percent.  In the current research study the risk of DM augmented
with the severity of COPD. The research study also established that the risk of
CVD and HTN is considerably in COPD individuals compared to the general populace.
The research study also recognized that the risk of CVD and HTN also augmented considerably
with severity of COPD. The research study also recognized that augment in the figure
of co-morbidities in COPD leads to increase in the severity of the ailment,
frequent emergency visits, exacerbations, limited physical activity, high
symptom score and poor quality of life as per DOSE score.

strength of the study was that it was a big sample size; it focused on particular
collection of subjects (COPD) at high jeopardy of DM, HTN and CVD individuals
who are symptomatic and aged. The selection was based not merely on the
symptomatology but as well on an in depth individual appraisal by a multi-disciplinary
team which was the cardiologist, pulmonologist and a general physician that
took into account medicinal history, jeopardy factors, physical assessment, blood
tests and all other important examinations to arrive at the diagnosis of co-morbidities.

The limitation
of the study was the fact that it is a solitary centric cross-sectional study
and therefore the results of the assessment cannot be widespread. The study did
not comprise previous co-morbidity similar to skeletal muscle dysfunction;
depression that COPD shows, these might have also added to the results.

Cohort study

et al 2013 undertook a research study to evaluate if type 2 diabetes (T2DM) is
an independent risk predictor for severe osteoarthritis (OA). The study design
was a cohort study with age and sex-stratified random sample of nine hundred
and twenty-seven men and woman aged forty to eighty years and was trailed over twenty
years from 1990 to 2010. The research study population was recruited in 1990
baseline as a random sample stratified in proportion to age and sex of all population
of Bruneck. A total of nine hundred and twenty-seven men and women was recruited
and trailed up until 2010 with assessments carried out every five years that is
1990, 1995, 2000, 2005 and 2010 and participation rate >90. Information T2DM
and arthroplasty was obtainable in all nine hundred and twenty-seven applicants
including five hundred and seventy-six applicants who were still living in 2010
and three hundred and fifty-one individuals who died throughout 20 years of trail
up. The study protocol of the Bruneck study was reviewed and accepted by the
ethics committees of Bolzano and Verona and all study applicants gave their
written informed permission (Schett et al 2013).

baseline and every five year trail up demographic and socioeconomic
characteristics, co-morbidities and medicines were recorded. Information was recovered
from (1) clinical history, (2) complete physical and neurologic
examinations and (3) measures such
as blood pressure recording, electrocardiography and carotid ultrasonography.
The presents of T2DM was diagnosed according to the American Diabetes
Association criterion. Localization, date and conditions of total hip and knee
arthroplasty that happened as from 1990 and 2010 was carefully recorded using
three sources of information (1) individual self report, health check up records
of the Brunel hospital and general practitioners and a standard  assessment of all radiographs even taken on
study individuals (Schett et al 2013).

the 2010 trail up exam, a total of five hundred and seventy-six subjects were
still living and had full data on arthroplasty and of these four hundred and
eight-eight applicants in fourth trail up. The self-directed questionnaires of
the knee injury and osteoarthritis results score and the Western Ontario and
McMaster University Osteoarthritis Index (WOMAC) both addressed the severity symptoms
associated with OA was filled out by three hundred and forty-seven men and
women who did not differ from the whole cohort of four hundred and eight-eight
applicants in any of the populace characteristics assessed (  Schett et al 2013).

was analysed by means of the statistical packages SPSS and STATA version 10.1
(StataCorp). At baseline sixty-nine of the nine hundred and twenty-seven
applicants of Bruneck research study meet the diagnostic criterion for T2DM.
Mean HbAic at baseline was 7.2%. Oral ant- diabetic medicines were used in
forty-one and insulin in three of the sixty-nine applicants. A total of thirty-one
of the sixty-nine applicants with diabetic had medical signs of a
polyneuropathy at baseline and this ratio augmented to 55.1% during trail up.
No individuals have been pretentious by T1DM. Between 1990 and 2010, thirteen
arthroplasties due to severe symptomatic hip/knee OA were performed in diabetic
individuals corresponding to an intercession rate of 17.7 per 1000 person-years
(Schett et al 2013).

The connection
linking OA and T2DM suggests that alterations in glucose metabolism directly have
an effect on joint integrity independently of body weight and creates an
opportunity for anticipating that sufficient controls of glucose metabolism hold
back the development of OA. The information illustrates that T2DM is a strong
predator for the growth of severe OA. In spite of the evidence from
cross-sectional research studies that OA is linked to the metabolic syndrome
and high blood glucose levels no research study addressed whether diabetes is  independently linked to OA and in particular
whether such a link is independent of body weight. This research study is the initial
study to demonstrate that T2DM foresees severe OA independent of age, sex and
BMI and provides both longitudinal and cross-sectional proof for an independent
association between type T2DM and OA (Schett et al 2013).

with diabetes may be given more medical attention than non-diabetic individuals,
leading to augmented attentiveness of or even over treatment of OA. Fear of
deterioration of the common medical condition in diabetic individuals could at slightest
theoretically guide to previous interventions in this group. In the present research
study radiographic severity of OA previous to surgery and the age at
arthroplasty together was identical in individuals with and without T2DM
suggesting no main dissimilarities in the indication for interventions in these
groups (Schett et al 2013).

strength of the research study was that the populace based design is strength
as well as it is a continuing and complete trail up and the use of joint
failure necessitates arthroplasty as a hard finishing point. The other strength
of the research study is the connection linking T2DM and OA which was reliable
when using 3 different approaches of OA ascertainment as follows joint failure
as determined by arthroplasty, signs and indications of OA as quantified by the
WOMAC and KOOS scores and the severity of joint alters as determined by
musculoskeletal US. Also the connection linking obesity and OA is entrenched
and above all supported by longitudinal information showing that obesity involves
a higher risk for developing severe OA (Schett et al 2013).

The limitation
of the study is that the numbers of arthroplasties are <100 which is measured as a limit to the research study outcomes. On the other hand arthroplasty are said to achieve the mainly severe disease phenotype of OA which is less common (Schett et al 2013). Randomized control trial Penn et al (2013) undertook a research study to see "the importance of weight loss maintenance and risk prediction in the prevention of type 2 diabetes (T2DM)" by means of lifestyle interventions with the plan of trying to increase physical activities, adjusting diet, and promote weight loss >5%. The research
study is a randomised control trial whereby applicants were allocated at a
random in a 1:1 ratio to an intensive lifestyle intercession to encourage more
physical activity and dietary modification or to a minimum lifestyle recommendation
control group. Applicants had a clinical assessment, as well as an Oral Glucose
Tolerance Test (OGTT) anthropometric and blood biochemistry measurements at
baseline and annually thereafter (Penn et
al 2013).

over forty years with BMI >25kgm or family history of T2DM in the SLIM research
study and with IGT defined as plasma glucose 7.8 to 11.0mmol two hours following
a standard fasting Oral Glucose Tolerance Test. The exclusion criterion was
diagnosis of T2DM, chronic illness making involvement in moderate physical
activity unfeasible and medication that would compromise the intercession. Intercession
objectives were based on a normal protocol and included weight loss decrease of
>5%, moderate physical activity for slightest thirty minutes per day or
equivalent and enhanced dietary quality with more fibre, reduced fat and
decrease saturated fat intake. Intercession delivery focused on individual
counselling including motivational interviewing. Physical activity and food diaries
completed quarterly facilitated personalised recommendation delivered by skilled
health professionals (Penn et al

group applicants were given short written information and verbal information regarding
a healthy diet and what is achieved on physical activity. The prime outcomes
were impact of life style intercession on T2DM occurrence. Secondary results
were weight loss, improved physical activity and enhanced dietary quality
sample size was determined for the DPS with eighty percent power and ninety-five
percent significance to detect thirty percent decrease of T2DM occurrence in
the intercession group compared with the control group (Penn et al 2013).

the three European Diabetes Prevention Study (EDIPS) cohorts recruited a total
of seven hundred and seventy-one applicants and followed them up during 3.1
years. In the intercession group one hundred and fourteen achieved >5%
weight loss at one year, one hundred and five maintained their weight at year two
and eighty-six at year three while in the control group fifty achieved >5%
weight loss at year one, twenty-six maintained this at year two and eighteen at
year three. Cox- regression analysis of pooled information illustrated that
applicants who achieved >5% weight loss at year one had sixty-four percent
lower T2DM occurrence, those who maintained this at year two had seventy-nine
percent lower T2DM risk and those who maintained this at year three had eighty-nine
percent low T2DM risk. There were no statistically considerable different
differences in any of the baseline variables for those who met, or did not meet
these weight loss goals other than a little lower baseline age for those accomplishing
the weight loss goal in the first year (Penn et al 2013).

The analysis
obtained supports existing proof for the effectiveness of intensive lifestyle
intercessions to prevent T2DM in adults with IGT and gives proof for the generalisability
of such intercession to European populations. Occurrence of T2DM decreased by
57% in the intercession group compared with the control group (Penny et al 2013).

strength of the research study was that the EDIPS RCTs were carried out in
three ethnically different populations, recruited over a ten year and the standardization
of finding in different countries corroborates the generalisability of the
lifestyle intercession originally planned for the DPS. The EDIPS protocol was universal
in all three groups. The research study also established improvement in weight
loss by means of lifestyle changes intercessions. The approach acknowledged the
need for some local differences in intervention delivery to achieve cultural
resonance, but the intercession goals, strengths and mode of delivery were the
same. Alterations to diagnostic criterion for T2DM since the design of EDIPS
would have left out some applicants because they would have been diagnosed with
T2DM for the duration of recruitment (Penn et
al 2013).

The limitation
of this research study was that it was carried out on white European
populations while in people of South Asian or African origin ethnicity, T2DM
risk is high. Effectiveness of lifestyle based interventions for T2DM avoidance
in these populations was established but not in Europe so far (Penn et al 2013).


importance of epidemiology is that it saves
money during the course of prevention. The investigation would recognize the
reason of the outbreak and show the way to interventions to prevent more cases
of the disease happening. Cohort
studies trail a group of individuals to determine if the developments of the
out of interest are different between groups with different exposures to
jeopardy factors. Randomised Control Trials gives the most excellent estimated
of the beneficial effects of treatment. Cross-sectional studies are studies in
which groups of individuals of diverse types are collected and put into one
large sample size group and studied at only a single point. Case control
studies are generally retrospective, applicants with the outcome of interest
are matched alongside applicants from the source population who do not have the
outcome variable.








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