Cross-sectional study Yuriko Suzuki, MD, MPH, PhD National Institute of Mental Health, NCNP...
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Transcript of Cross-sectional study Yuriko Suzuki, MD, MPH, PhD National Institute of Mental Health, NCNP...
Cross-sectional studyCross-sectional study
Yuriko Suzuki, MD, MPH, PhDNational Institute of Mental Health, NCNP
Key issuesKey issues
• Why research?
• Descriptive study
• Hypothesis testing
• Association
• Sampling
• An example of cross-sectional study
Why research?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
What is a hypothesisWhat 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
ExampleExample
• 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
Advantages of hypothesis-Advantages of hypothesis-driven researchdriven research
• Greater credence given to validity of findings
• Less risk of type I and II errorso Type I error: mistakenly see association while
there isn’t.o Type II error: mistakenly see no association
while there is.
• Ease of replication
What do epidemiologists What do epidemiologists do?do?
• Describeo Distribution of health-related states in a populationo Extent, type, severityo Who, where, when?
• Explaino Analytical epidemiologyo Hypothesis-driven etiological researcho Risk factors and causes
• Evaluateo Quasi-experimental studieso Randomized controlled trials
Association Association
Risk factor
Disease
Exposure Outcome
Independent
Dependent
ChanceBias
Confounding
True association?
Descriptive studiesDescriptive studies• Case series
• Cross-sectional studyo Multi-center (geographic variance)o Ecological correlation o Repeated surveys (temporal variance)
Who to study?Who to study?• Population
• Sampleo Advantage:
• time and costo Disadvantages:
• sampling error, • bias if sample is not representative of population
Random samplingRandom sampling
• Simple
• Systematic
• Stratified
• Multi-stage and cluster
How big a sample?How big a sample?
• Sample size calculation is important to avoid errors in interpreting findings:
• Type I errors: o The null hypothesis is rejected when it is in
fact, true (p value)• Type II errors:
o The null hypothesis is accepted when it is, in fact, false (power)
Prevalence study
• 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 13
Niigata
Earthquakes in NiigataEarthquakes 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 deaths 4805 injuries
• 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 deaths 2345 injuries
Prevalence of mental health disorders among community dwelling elderly three year after the Niigata-Chuetsu earthquake
1. Face-to-face interviews were conducted to the older people above 65 in the severely damaged area by the Niigata-Chuestu earthquake
2. Diagnoses of mental disorder were confirmed using Mini International Neuropsychiatric Interview (M.I.N.I.), and quality of life (QOL) were measure by WHOQOL
3. The prevalence and its associated factors were described.
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4. Data collection Trained health professionals administered the
questionnaires and the following structures interviews;
5. MeasurementA) Diagnosis of mental disorders (M.I.N.I.)
a. Major depression (current, since the earthquake)b. Minor depression (current, since the earthquake) c. Suicidal tendency (current, since the earthquake)d. Posttraumatic stress disorder (current)e. Alcohol dependence and abuse (current)
B) QOL : WHO/QOL-BREFa. Physicalb. Psychologicalc. Sociald. Environmental
MethodsMethods
Community-dwelling older adults (n=799)
Population of the older adults (65 and over) in the severely affected areas in Ojiya city (n=902)
ExclusionDead (n=42)Hospitalized (n=20)Institutionalized( n=15
)Moved out (n=24)
Completed interviews (n=496), Completion rate 62.1%
Unable to interviewAbsents (n=27)Due to disability (hearing, seeing, etc) (n=71)
Refusal to interview (n=215)
Results (1): Flow of the study (2007.10.1-2008.1.11)
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ResultsResults (( 22 ))Table 1. Characteristics of participants of the study of three year after the Niigata-Chuetsu earthquake in 2004 (n=473) n % Mean 95% CIGender
Male 190 40.2 Age
65-74 209 44.2 75+ 264 55.8 Average age 76.0 75.4-76.6
Marital statusMarried 328 69.3 Divorced 3 0.6 Bereaved 140 29.6 Never married 2 0.4
EducationElementary school 128 27.5 Koutouka 112 24.0 Chugakko 167 35.8 Koukou 20 4.3 Others
Numbers of year in education 8.2 8.1-8.4Number of cohabitant 3.9 3.7-4.1Previous psychiatric visit 19 4.3
Digit spam (3 digits) Incorrect 29 11.2
Severity of disaster damageResultsResults (( 33 )) I. Prevalence
study
Prevalence of mental disorders in 2 weeks and past 3 years Prevalence of mental disorders in 2 weeks and past 3 years
among the older people living in community by gender (n=444)among the older people living in community by gender (n=444)
Results ( 4 )
**
**
**:p<0.05
2w 3yMajor depression
2w 3yMajor and Minor depression
Current PTSDEarthquake Other events
Current alcohol-dependence, abuse
2w 3ySuicidal tendency
Pre
vale
nce
rate
(%
)
**
**
(n=446) (n=443) (n=245) (n=445) (n=88) (n=51)
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
Results ( 7 )
QOL mean : male 3.54 (95%CI:3.47-3.60) female 3.48 (95%CI:3.43-3.53)
Results ( 8 ) Results of regression analysis for quality of life and interviewees’ basic characteristics (n=439)Variables Physical Psychologic
al Social Environmental Mean QOL score
Coef. Coef. Coef. Coef. Coef.Gender -0.05 -0.07 0.07 -0.10 * -0.05 (male=0, female=1)
Age -0.01 0.00 0.00 0.00 0.00 year
Marital status 0.03 0.01 -0.08 -0.04 0.00 (not married=0, married=1)
Number of cohabitants 0.02 0.03 * 0.02 0.03 ** 0.03 *
Years in education -0.03 0.00 0.00 -0.01 -0.01
Previous psychiatric visit -0.13 -0.03 -0.06 0.04 -0.03
(never=0, yes=1)
Severity of disaster damage in 2004
-0.05 * -0.03 -0.04 -0.03 -0.04 *
Physical illness -0.29 ** -0.17 ** -0.01 0.00 -0.15 **
Intercept 4.9 3.6 4.1 3.6 3.9 Adjusted R2 0.060 0.022 0.003 0.015 0.034 *:p<0.05, **:p<0.01
• 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
Discussion ( 1 )
• 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.
Discussion ( 2 )