Epidemiology Assignment: Arsenic Exposure and Health Outcomes

This epidemiology assignment analyzes a study conducted in Bangladesh, investigating the correlation between arsenic exposure from drinking water and mortality rates, including all-cause and chronic disease deaths. The study employed a cohort design with multiple follow-ups to assess the impact of arsenic exposure levels on health outcomes. The assignment addresses the study's objectives, methodology, participant selection, and limitations, particularly regarding loss of follow-up. The findings reveal a significant association between chronic arsenic exposure and increased mortality, with higher arsenic levels linked to elevated hazard ratios. The assignment explores the use of primary exposure variables like marital status, gender, and age, and discusses the influence of confounding variables such as body mass index. It also interprets the 95% confidence intervals and multivariate hazard ratios, highlighting the study's conclusion that arsenic exposure from drinking water poses a substantial health risk, emphasizing the need for public health interventions to mitigate these effects. The study's use of age-standardized ratios to compare risks over time is also discussed.

Running head: EPIDEMIOLOGY 1
Epidemiology
Name
Date of Submission

EPIDEMIOLOGY 2
Q1
The main aim of this study was to assess progressively whether recent exposure to
arsenic from drinking water and chronic infections were associated with all causes as well as
chronic disease deaths among the population in Bangladesh.
Q2. The criteria used for the selection of the study participants in this case was random
sampling upon meeting the inclusion and exclusion criteria. An advantage of this method is that
it gives and opportunity for any member of the population to be chosen as part of the sample. A
disadvantage of random sampling is that there are some features of the sample that are not part of
the study question and these might act as sources of bias.
Q3. The researchers were not able to get rid of loss of follow-up. This is because
although the research was structured in a way of active follow-up to the cohort. In this case, the
follow-up was structured in the phases throughout the study period. The first follow-up was
conducted between sept 2002 to May 2004, the second was in June 2004 to August 2006, and
thirst follow-up was from January 2007 to February 2009. In these follow-ups, there are some
months which have not been accounted for, and probably, there could be some losses of follow-
ups (Argos et al., 2010).
Q4. the results of this study indicated that there were 407 deaths between October 200 to
February 2009. The obtained multivariate adjusted hazard ratios for the all-cause mortalities as
compared to arsenic levels in 10.1-50, 50.1-150, and 150-864, with 10 least being in water
samples from well water was 1.34 at 95% CI, and 1.68 respectively. However, these findings
were similar to daily arsenic doses as well as the arsenic contained in urine. These findings
indicated that the chronic exposure to arsenic through drinking water was linked to increased
death rates among the population in Bangladesh. The data from this follow up study can be used

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to determine the long-term effects of exposure to arsenic from drinking water and the possible
effects of these exposure to the long-term effects. Additionally, the findings recommend the
adoption of relevant measures to counter the effects of human exposure to arsenic in drinking
water.
Q5. Advantage:
a. source of rich datasets for a research
b. It gives detailed information concerning the subject.
Disadvantage:
a. It is time consuming in terms of integrating different information to make a meaningful
conclusion.
b. It requires close keenness and thus might be subject to errors in making
ascertainments.
Q6. a. The primary exposure variables in this case were marital status, gender age and
arsenic. Gender was an important variable because there were variations of arsenic chronic
effects among men and women. Age was also relevant variable because the study participants
were required to be in the range of eighteen to seventy-five years. Marital status was an
important exposure because the households are the major source of contamination due to
consumption of contaminated drinking water.
b. The advantage of using marital status as a primary exposure variable is that it is
indicative that the family point is a possible point of exposure to arsenic in drinking water. It is at
the household levels that many people are likely to get exposed to arsenic levels in a short
duration of time. However, a disadvantage of this primary exposure variable is that being

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married does not indicate the presence of many family members, while others could not be living
with their families.
Q7. In this article, there is an evidence of the body mass index being a confounding
variable to the arsenic exposure. In table 1, an increase in body mass index was associated with
increase in arsenic exposure in drinking water. At the same time, the body mass index is a strong
confounder of all-cause mortality.
Q8. The 95% confidence interval means that the used sample, in this study, if taken in a
repeated manner 95% of the intervals would fall within the population mean. In this case, at 95
% confidence interval, the interval has a probability of 0.95 of having the population mean. In
this article, the quadrant that indicated a 15% increase in all-cause mortality had a 0.95
probability of falling within the one quartile.
Q9. The probability of multivariate hazard ration for making a comparison to baseline
arsenic levels at a frequency of 1.46 level would be 0.95. these means that after the first follow-
up, the likelihood of hazard occurring was at 1.46.
Q10. This study found that there were some significant association between exposure to
arsenic from water and mortality rates. Additionally, the exposure to arsenic as measured from
the arsenic in urine was associated with all-cause mortality. At the same time, the mortality rates
were increasing as the level of arsenic were increasing in contaminated drinking water. The data
indicated that a trend of risk of arsenic exposure was high in the exposed population (Chen et al.,
2009). The association between arsenic concentrations in water collected water from wells and
mortality never indicates significant changes, and thus possibility of medical disorders which can
also act as confounding effects.

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Q 11. This is an indication that the presence of arsenic from drinking water collected
from the wells causes a chronic infection to a proportion of 24% of the total population in this
study. The researchers thus found that as the exposure to arsenic from water increased, so did the
risk of all- cause mortality as a result of chronic disease deaths also increase.
Q12. The age standardized ratios are very important in comparing the risks of events in
two different time frames. In this case, one population needs to be adjusted so as to have the
same structure of age as the other population.
First the age specific is calculated for every age group; whereby the number of deaths are
divided by the population and then multiplied by 100,000.
Then each of the age specific rates are multiplied by the proportion of the people who
belong to a certain age group.
As indicated in table two, the new standardized information indicates that the incidence
rate is 3330 per every 100,000 person years with various age distributions.
(Incidence rate divided by the person at risk) multiplied by 100,000
=(2714.4/3330 ) *100000
=81513 per every 100,000 people.

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References
Argos, M., Kalra, T., Rathouz, P. J., Chen, Y., Pierce, B., Parvez, F., ... & Sarwar, G. (2010).
Arsenic exposure from drinking water, and all-cause and chronic-disease mortalities in
Bangladesh (HEALS): a prospective cohort study. The Lancet, 376(9737), 252-258.
Chen, Y., Parvez, F., Gamble, M., Islam, T., Ahmed, A., Argos, M., ... & Ahsan, H. (2009).
Arsenic exposure at low-to-moderate levels and skin lesions, arsenic metabolism,
neurological functions, and biomarkers for respiratory and cardiovascular diseases:
review of recent findings from the Health Effects of Arsenic Longitudinal Study
(HEALS) in Bangladesh. Toxicology and applied pharmacology, 239(2), 184-192.