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Presented at a Research Methods course at the Northern Area Armed Forces Hospital on December 28, 2020 3.40pm by Dr Omar Hasan Kasule Sr Professor of Epidemiology and Bioethics, King Fahad Medical City.
STEPS OF AN EPIDEMIOLOGICAL INVESTIGATION
• Identifying and describing a problem
• Using the scientific method to formulate and test hypotheses
• Interpreting findings.
TWO TYPES OF EPIDEMIOLOGICAL STUDIES
• Observational: get information on disease and causes without interfering with nature
• Experimental: manipulate the causes artificially to see the effect on disease
SOURCES OF EPIDEMIOLOGICAL INFORMATION FROM EXISTING DATA
• Census
• Medical facilities: government and private sector
• Health surveys
• Vital statistics
SOURCES OF EPIDEMIOLOGICAL INFORMATION FROM OBSERVATIONAL STUDIES
• Observational studies allow nature to take its course and just record the occurrences of disease
• Observational studies describe the what, where, when, and why of a disease.
• Observational studies do not interfere with the cause or the outcome
SOURCES OF EPIDEMIOLOGICAL DATA FROM EXPERIMENTAL STUDIES
• Experimental studies are natural or true experiments
• They involve deliberate human action or intervention whose outcome is then observed.
• They have the advantage of controlled conditions
• They have ethical problems of experimenting on humans..
TYPES OF OBSERVATIONAL STUDIES
• Cross-sectional studies including ecological studies and surveys
• Case-Control studies
• Follow-up (cohort) studies
TYPES OF EXPERIMENTAL STUDIES
• Laboratory-based experimental studies
• Community based experimental studies
• Randomized clinical trials
• Non-randomized clinical studies
EXAMPLE OF RESEARCH BASED ON OBSERVATIONAL DATA - 1
Yamanaka H et al. A large observational cohort study of rheumatoid arthritis, IORRA: Providing context for today's treatment options. Mod Rheumatol. 2020 Jan;30(1):1-6. Real-world evidence, based on real-world data from routine clinical treatment, is becoming increasingly important for providing high-quality medical care. Large-scale cohort studies can provide useful access to some of this real-world evidence, as shown by the IORRA (Institute of Rheumatology, Rheumatoid Arthritis) cohort in Japan. This large cohort study of patients with rheumatoid arthritis (RA) has been surveying enrolled participants since its inception in
2000. In the last 19 years, it has served as a database for a wide range of research in areas including transitions in medical care at the clinical level, changes in therapeutic drugs, approaches to comorbidities, developments in pharmacoeconomics, and the effects of genomic information on treatment options. This research has resulted in the publication of 133 articles in English to date. IORRA monitors changes in the management of RA, and has quantified over time the daily experience of clinicians who provide routine medical care. Such observational databases, which reflect the reality of daily clinical practice, will become increasingly important and may provide a model for similar research in other disease areas.
EXAMPLE OF RESEARCH BASED ON OBSERVATIONAL DATA - 2
Aranda-Abreu GE et al. Observational study of people infected with SARS-Cov-2, treated with amantadine. Pharmacol Rep. 2020 Dec;72(6):1538-1541.
BACKGROUND: We conducted an observational study of 15 patients from a Southeastern area of Mexico with symptoms compatible with SARS-Cov-2, which were treated with the antiviral amantadine. METHODOLOGY: In this study, data were collected from 15 individuals with clinical symptoms of COVID-19 infection, which were treated on an ambulatory basis with 100 mg of amantadine for a period of 14 days. RESULTS: This drug demonstrated its effectiveness, as patients recovered successfully with this treatment without the necessity of attending a hospital to use mechanical ventilation. All patients developed IgG antibodies to
SARS-Cov-2. CONCLUSION: Amantadine can be used as a viable and cost-effective alternative
for treating people with severe acute respiratory syndrome (SARS-Cov-2) on an
ambulatory basis, while the vaccine is not available.
EXAMPLE OF RESEARCH BASED ON OBSERVATIONAL DATA - 3
Godos J et al. Dairy foods and health: an umbrella review of observational studies. Int J Food Sci Nutr. 2020 Mar;71(2):138-151.
Evidence on the consumption of dairy foods and human health is contradictory. This study aimed to summarize the level of evidence of dairy consumption on various health outcomes. A systematic search for meta-analyses was performed: study design, dose-response relationship, heterogeneity and agreement of results over time, and identification of potential confounding factors were considered to assess the level of evidence. Convincing and probable evidence of decreased risk of colorectal cancer, hypertension, and cardiovascular disease, elevated blood pressure, and fatal stroke, respectively, was found for total dairy consumption; possible decreased risk of breast cancer, metabolic syndrome, stroke, and type-2 diabetes, and increased risk of prostate cancer and Parkinson's disease was also found. Similar, yet not entirely consistent evidence for individual dairy products was reported. Among potential confounding factors, geographical localization and fat content of dairy have been detected. In conclusion, dairy may be part of a healthy diet; however, additional studies exploring confounding factors are needed to ascertain the potential detrimental effects.
EXAMPLE OF A RESEARCH-BASED ON EXPERIMENTATION
Eğilmez OK et al. Investigation of the Protective Effect of Nigella Sativa Oil in Cisplatin
Induced Oral Mucositis: An Experimental Study. Turk Arch Otorhinolaryngol. 2020 Mar;58(1):10-15.
OBJECTIVE: The aim of this experimental study was to investigate the histopathologic effect of Nigella Sativa oil (NSO) on cisplatin (Cis) induced oral mucositis (OM) in rats. METHODS: Twenty-four rats were divided into four equal groups. The animals in Group 1 and Group 2 were given 5 mg/kg intraperitoneal (ip) Cis systemically on the 1st, 3rd, and 5th days of the study. Additionally, 15 mL NSO was given to the rats in Group 2, with gavage feeding on days 1, 3, 5, 7, and 9. The animals in Group 3 were given per oral 15 ml NSO on days 1, 3, 5, 7, and 9. As the control group, Group 4 received a total of 15 mL 0.9% saline solution divided into 5 doses on days 1, 3, 5, 7, and 9 by oral gavage. On the 14th day, animals were euthanized and buccal mucosa from both sides, including submucosal tissues, were excised and taken to histopathological examination. RESULTS: The mean mucosal thicknesses of the groups were 224.58 μm, 276.1 μm, 323.33 μm, and 331.33 μm, respectively for Groups 1, 2, 3, and 4 (p<0.05). When the degree of mucosal inflammation was examined, the most intense inflammation was detected in Group 1 and the least intense inflammation was in Group 4
(p<0.01). The degree of inflammation in Group 2 and Group 3 was similar to Group 4 (p>0.05). CONCLUSION: According to the results of this study, NSO, for which anti-inflammatory and antioxidant properties have been shown in previous studies, may also be effective in preventing Cis-induced OM.