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Cross-sectional study

Cross-sectional study. Yuriko Suzuki, MD, MPH, PhD National Institute of Mental Health, NCNP yrsuzuki@ncnp.go.jp. Key issues. Why research? Descriptive study Hypothesis testing Association Sampling An example of cross-sectional study. Why research?. To guide health practice and policy

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Cross-sectional study

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  1. Cross-sectional study Yuriko Suzuki, MD, MPH, PhD National Institute of Mental Health, NCNP yrsuzuki@ncnp.go.jp

  2. Key issues • Why research? • Descriptive study • Hypothesistesting • Association • Sampling • An example of cross-sectional study

  3. Why research? • To guide health practice and policy • Because local research is often needed to guide local health practice and policy • Because carrying out research strengthens research capacity

  4. What is a hypothesis • A statement which describes what you expect to find in a specific manner • Clearly stated • Testable and refutable • Not a mere research question or objective • Backed by sample size calculation, and an appropriate design and analysis

  5. Example • Statement of the problem: mental health problems are said to be common in the aftermath of a disaster, and mental health problems are believed to be associated with physical damage • Aim: to describe the association between physical damage and mental health problems • Question: Are mental health problems associated with physical damage in time of disaster? • Hypothesis: elderly people with poor mental health are more likely to have severe housing damage in time of disaster

  6. Advantages of hypothesis-driven research • Greater credence given to validity of findings • Less risk of type I and II errors • Type I error: mistakenly see association while there isn’t. • Type II error: mistakenly see no association while there is. • Ease of replication

  7. What do epidemiologists do? • Describe • Distribution of health-related states in a population • Extent, type, severity • Who, where, when? • Explain • Analytical epidemiology • Hypothesis-driven etiological research • Risk factors and causes • Evaluate • Quasi-experimental studies • Randomized controlled trials

  8. Association Risk factor Disease True association? Exposure Outcome Independent Dependent Chance Confounding Bias

  9. Descriptive studies • Case series • Cross-sectional study • Multi-center (geographic variance) • Ecological correlation • Repeated surveys (temporal variance)

  10. Who to study? • Population • Sample • Advantage: • time and cost • Disadvantages: • sampling error, • bias if sample is not representative of population

  11. Random sampling • Simple • Systematic • Stratified • Multi-stage and cluster

  12. How big a sample? • Sample size calculation is important to avoid errors in interpreting findings: • Type I errors: • The null hypothesis is rejected when it is in fact, true (p value) • Type II errors: • The null hypothesis is accepted when it is, in fact, false (power)

  13. Prevalence study Niigata Suzuki Y, Tsutsumi A, Fukasawa M, et al. Prevalence of mental disorders and suicidal thoughts among community-dwelling elderly adults 3 years after the niigata-chuetsu earthquake. J Epidemiol. 21:144-50. 2011

  14. Earthquakes in Niigata • In 2004: The Niigata-Chuetsu earthquake • 2004.10.23.5:56pm • Magnitude:6.8 in Richter scale • Seismic intensity:7 in Japanese scale • Damage:68 deaths4805injuries • In 2007: The Niigata Chuetsu-oki earthquake • 2007.7.16.10:13am • Magnitude:6.8 in Richter scale • Seismic intensity:6 in Japanese scale • Damage:15 deaths2345injuries

  15. Prevalence of mental health disorders among community dwelling elderly three year after the Niigata-Chuetsu earthquake • Face-to-face interviews were conducted to the older people above 65 in the severely damaged area by the Niigata-Chuestu earthquake • Diagnoses of mental disorder were confirmed using Mini International Neuropsychiatric Interview (M.I.N.I.), and quality of life (QOL) were measure by WHOQOL • The prevalence and its associated factors were described.

  16. Methods • Data collection Trained health professionals administered the questionnaires and the following structures interviews; • Measurement • Diagnosis of mental disorders (M.I.N.I.) • Major depression (current, since the earthquake) • Minor depression(current, since the earthquake) • Suicidal tendency(current, since the earthquake) • Posttraumatic stress disorder (current) • Alcohol dependence and abuse (current) • QOL：WHO/QOL-BREF • Physical • Psychological • Social • Environmental

  17. Population of the older adults (65 and over) in the severely affected areas in Ojiya city (n=902) • Exclusion • Dead(n=42) • Hospitalized (n=20) • Institutionalized( n=15) • Movedout(n=24) • Community-dwelling older adults (n=799) Results（１）：Flow of the study (2007.10.1-2008.1.11) • Completed interviews (n=496), Completion rate62.1% • Unable to interview • Absents(n=27) • Due to disability (hearing, seeing, etc) (n=71) • Refusal to interview (n=215)

  18. Results（2）

  19. Results（3） I. Prevalence study Severity of disaster damage

  20. Prevalence of mental disorders in 2 weeks and past 3 years among the older people living in community by gender (n=444) Results（4） Prevalence rate (%) ** ** ** **:p<0.05 ** 2w3y Major and Minor depression 2w3y Suicidal tendency 2w3y Major depression Current PTSDEarthquake Other events Current alcohol- dependence, abuse

  21. Results（5） The percentage of those who met criterion A and B of PTSD in DSM-IV-TR by exposure of the earthquake and the other events (n=446) (n=443) (n=245) (n=445) (n=88) (n=51)

  22. Results（7） QOLmean : male 3.54 (95%CI:3.47-3.60) female 3.48 (95%CI:3.43-3.53)

  23. Results（8）

  24. Discussion（1） • Prevalence of major depression and PTSD was lower than previous researches in disaster settings in other countries（6.4-11%, 4.4-25% respectively in literature）. • The prevalence of major depression since the earthquake was 4.4%, within the range of the prevalence in non-disaster community studies (0.9-9.4% in literature). • Among males, the alcohol related problems were reported in 6.0% and among females, major or minor depression were reported in 10.0%, and suicidal tendency were seen in 8.0% of the interviewees. • Pathological level→about same level as usual • Subclinical level → require further attention to promote their mental health

  25. Discussion（2） • In general, having fewer cohabitants, and greater degree of disaster damage, and any physical illness were attributing to the worse quality of life. • The risk factors for poor QOL were severity of disaster damage, and physical illness in physical domain, fewer cohabitants and physical illness in psychological domain, being female, and fewer cohabitants in environmental domain. • Mental health and physical health care would be better if provided hand in hand, and social support persistently had favorable effects on QOL among disaster affected elderly people.

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