Research Methods - 25-hydroxyvitamin D and depressive symptoms

Running head: RESEARCH METHODS 1
Research Methods
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1) The study aimed at determining the association between 25-hydroxyvitamin D and depressive
symptoms among older adults. Hypovitaminosis D is a condition that is common among senior
adults and is caused by the deficiency in Vitamin D which has further been associated with poor
health and chronic diseases (Stewart & Hirani, 2010). It is therefore suggested that
Hypovitaminosis D is likely to be a contributing factor to depression among older adults
(Milaneschi et al., 2010).
2) Population-based cohort study. This study design has multiple strengths. The outcomes of
such a study design apply to a specific population and thus eliminating selection bias. It also
allows the calculation of the population estimates, distribution and incidence rates. Additionally,
the design allows the unbiased study of the association of confounders to exposures and results
including those undefined in the initial research hypotheses (Strobe Initiative, 2014). On the
other hand, a population-based cohort study requires more time and is much costlier. It also
requires a larger sample size and is prone to misclassification and follow-up bias (Sorlie & Wei,
2011).
3) Women and men with 25(OH)D less than 50 nmol/l had increases in CES-D scores of 2.1 and
1.9 respectively. Low vitamin D in both men and women was a significant predisposing factor
for developing a depressed mood with a hazard ratio of 1.6 and 2.0 respectively. Therefore,
Hypovitaminosis D is a predisposing factor for depression among elderly adults with women
being affected the most. The outcome is thus consistent with the main objective because it shows
the association between the study variables as indicated in the objective
4) a) The study provides a basis for future research by exploring research that has not been
carried out by previous researchers. The study provides the strongest scientific evidence because
it identified the exposure before the results.
b) However, the study considers only one risk factor of depression among the elderly, yet there
exist other several aspects of vitamin D deficiency that influences depression.
5) The discussion and conclusion section of the study has been integrated effectively. The
current results have been examined in the context of current research knowledge. For instance,
the section cites the relevant findings of previous studies on relatively similar research and then

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compares with the current study to point out the research gap that has been filled by the present
study. The discussion section is of high quality because it also includes the strengths and
limitations of the study. This is critical because it shows whether the outcomes can be reliable or
not. Furthermore, the discussion section provides on how the limitations could not be significant
to the extent that they affect the general outcome of the study. The conclusion is based on the
outcomes, addresses the research objective and nothing new is introduced.
The study has multiple implications. The outcomes of the study can be used by healthcare
professionals to help control the prevalence of depression among older adults by first
ascertaining their vitamin D status. Nutritional experts can also make use of the outcomes to
recommend a relatively high consumption of foods fortified with vitamin D to the older adults.
The ministry of health could also utilize the findings to help control the increasing depression
among older adults by making policies on the construction of aged care centers that allow sun
exposure. The large sample size used in the study implies that the findings can be generalized to
any population of older adults.
6) No. the results of the study were not valid. First, the loss of participants to follow-up was
significant. Secondly, the lost participants were older and more affected by chronic illness than
those that remained for assessment thus limiting the generalization of the results of the study.
Other researchers have also indicated that significant loss of participants to follow-up in cohort
studies substantially affects the validity of the outcomes in cohort studies more so when the loss
to follow-up is also differential (Boffetta, 2011; Mann, 2012).
7) The study was unbiased because the researcher used the CES-D questionnaire to collect data
observed among the participants. The instrument has widely been used before to measure
depressive symptoms in the older population. Furthermore, the use of random selection during
selection minimized any chances of selection bias in addition to the use of a selection criteria.
The large sample size made the results more generalizable thus improving its external validity.
study was also biased because of the significant loss of follow-up participants resulted in
selection bias.

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8) The outcomes of the study could be used in clinical practice in several ways. Clinical experts
could recommend the consumption of foods rich in vitamin D or exposure to sunlight when
presented with older adults experiencing depression and related illness among older adults. This
is because the current study confirms the association between the two variables. In other words,
the health experts can opt for the normalization of vitamin D levels as a method of treatment.
9) The study found out that vitamin D has a substantial effect on the functionality of the brain,
hence the causal association between the deficiency in vitamin D levels and the beginning of
depressive symptoms. However, the current evidence is not sufficient to confidently warrant the
causal association. Hence the need for future research to examine the potential causal pathway
between the deficiency in Vitamin D and depression.
10) The article was written most appropriately. First, the article follows the standard outline of
observation studies according to the STROBE Statement (Vandenbroucke et al., 2014). The
division of the article into subtopics and topics increases its readability in addition to the visual
presentation of the outcomes of the analyses in table format. Additionally, it was written in a
value-free language with both strengths and weaknesses being highlighted. Moreover, ethical
issues were addressed since the study procedure adhered to the Italian National Institute of
Research and Care on Aging Ethical Committee. Therefore, it can generally be concluded that
the article was written.

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References
Boffetta, P. (2011). Internal and external validity of cohort studies. Annals of Agricultural and
Environmental Medicine, 18(2).
Mann, C. J. (2012). Observational research methods—Cohort studies, cross sectional studies,
and case–control studies. African Journal of Emergency Medicine, 2(1), 38-46.
Milaneschi, Y., Shardell, M., Corsi, A. M., Vazzana, R., Bandinelli, S., Guralnik, J. M., &
Ferrucci, L. (2010). Serum 25-hydroxyvitamin D and depressive symptoms in older
women and men. The Journal of Clinical Endocrinology & Metabolism, 95(7), 3225-
3233.
Stewart, R., & Hirani, V. (2010). Relationship between vitamin D levels and depressive
symptoms in older residents from a national survey population. Psychosomatic
Medicine, 72(7), 608-612.
Sorlie, P., & Wei, G. S. (2011). Population-based cohort studies: still relevant?. Journal of the
American College of Cardiology, 58(19), 2010-2013.
Strobe Initiative. (2014). Strengthening the Reporting of Observational Studies in Epidemiology
(STROBE): explanation and elaboration. International Journal of Surgery, 12(12), 1500-
1524.
Vandenbroucke, J. P., von Elm, E., Altman, D. G., Gøtzsche, P. C., Mulrow, C. D., Pocock, S. J.,
... & STROBE Initiative. (2014). Strengthening the Reporting of Observational Studies in
Epidemiology (STROBE): explanation and elaboration. International journal of
surgery, 12(12), 1500-1524.