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Using and Interpreting Data

Using and Interpreting Data. Substance Abuse Epidemiology Unit Epidemiology and Response Division New Mexico Department of Health. Outline. Measures of relative frequency Calculating rates Examples Age-adjustment Trends Small group exercises Sources of data

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Using and Interpreting Data

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  1. Using and Interpreting Data Substance Abuse Epidemiology Unit Epidemiology and Response Division New Mexico Department of Health

  2. Outline • Measures of relative frequency • Calculating rates • Examples • Age-adjustment • Trends • Small group exercises • Sources of data • Review of the New Mexico State Epi Profile • Community examples

  3. Ratios • Ratio: a comparison of two groups • Groups may be unrelated or subgroups of a larger category • Ratio = A / B • Examples: miles / gallon students / teacher males / females (sex ratio)

  4. Proportions • Proportion: a relationship of one part to the whole, e.g. percentage, fraction, decimal • Percentage = __A__ x 100 A + B • Numerator is always included in the denominator • Examples: • ______# of females in class______ # of females + # of males in class • ___# of alcohol-related deaths in Sandoval county_____ Total # of alcohol-related deaths in all 33 NM counties

  5. Calculating Proportions - Example Proportion of alcohol-related (A-R) deaths in Sandoval county Numerator = # A-R deaths in Sandoval county = 213 Denominator = # A-R deaths in New Mexico = 5,068 Time Period = 1999-2003 Constant = 100 Proportion of statewide A-R = __213_ x 100 = 4.2% deaths in Sandoval county 5,068

  6. Prevalence • Prevalence = the number of existing cases or events in a certain population at a given point in time • Prevalence is a proportion and can be expressed as a percentage • Includes current cases/events • Must indicate WHEN cases were enumerated Prevalence = # of existing cases = 15_ = 0.10 X 100 or 10% Total population 150

  7. Prevalence- ExampleYouth Binge Drinking Chart 2: Binge Drinking by Sex and Grade Level, 2003 NM YRRS

  8. Rates • Frequency of a defined event in a specified population during a given time period • Incorporates time into the measure • Multiplied by a constant for ease of interpretation • Rate = # events (deaths, cases, etc.) _______# people at risk_____ time • Example: crude death rate

  9. Calculating Rates - Example 2002 all cause crude death rate for NM Numerator = # of deaths in NM during 2002 = 14,344 Denominator = total population of NM in 2002 = 1,853,030 Time Period = 2002 Constant = 100,000 Crude death rate = __14,344__ X 100,000 = 774.1/100,000 1,853,030 Source: CDC Wonder

  10. Age-adjustment of mortality rates • Death rate – number of deaths occurring in a specified population during a given period of time • Crude death rate – the death rate in the total population • Adjusted death rate – recalculation of the death rate using a standard population reference • Compensates for differences in the age distributions of populations being measured • Allows comparisons between groups

  11. Age-adjustment - Example • Crude death rate (1992-1994) • Mexico: 469.6/100,000 • US: 869.6/100,000 • Adjusted death rate (1992-1994) • Mexico: 596.6/100,000 • US: 519.1/100,000

  12. Trends • Looking at the same data over time • Data collected the same way over periods of time • Numbers large enough to calculate percentages or rates for each time period • Same length of time in each period used as a data point

  13. Alcohol-Related Motor Vehicle Crash Fatality Rates, New Mexico and US, 1990-2004 Source: Division of Government Research, University of New Mexico

  14. Drug-Related Death Rates* New Mexico and US, 1990-2004 *Rates are age-adjusted to the 2000 US population Sources: Bureau of Vital Records and Health Statistics, NMDOH; CDC Wonder

  15. Small Group Exercises

  16. New Mexico Crude Death Rates By County, 2002 Source: CDC Wonder

  17. New Mexico Age-Adjusted Death Rates By County, 2002 Source: CDC Wonder

  18. Common Sources of Health Data • Population and demographic data from the US Census Bureau and the Bureau of Business and Economic Research at UNM • Birth and death data from the NM Bureau of Vital Records and Health Statistics • Population-based survey data collected by the NM DOH • YRRS: Youth Risk and Resiliency Survey • BRFSS: Behavioral Risk Factor Surveillance System • Hospitalization in-patient discharge data from the NM Health Policy Commission

  19. New Mexico SPF-SIG State Epi Profile

  20. NM SPF-SIG State Epi Profile Provides a systematic and comprehensive overview of ATODA-related consequences ….

  21. NM SPF-SIG State Epi Profile … and ATODA-related consumption

  22. How to use this report Outcome indicators: consequences • Problem statement presents overview of the data and detailed statistics • Outcome indicators – associated with two tables • Number of deaths on the left side of the table • Age-specific death rates per 100,000 population on the right side of the table* • County bar chart showing age-adjusted rates for each NM county in descending order *Note: All-ages rate is per 100,000, age-adjusted to the 2000 US population

  23. How to use this report Outcome indicators – Table 1 • Table 1: deaths and death rates by sex, age group, and race/ethnicity • Useful in determining the most important risk groups at a statewide level

  24. How to use this report Outcome indicators – Table 1

  25. How to use this report Outcome indicators – Table 2 • Table 2: deaths and death rates for each NM county by race/ethnicity • Useful in determining: • Counties with the most severe substance abuse problems • Groups with the highest risk within each county

  26. How to use this reportOutcome indicators – Table 2 *All rates are per 100,000, age-adjusted to the 2000 US population

  27. How to use this report Outcome indicators – County bar charts • Number of deaths and the percent of NM deaths occurring in each county are given next to the county name on the left side • Highest death rates are at the top • State rate shown with a darker bar for comparison

  28. Alcohol-Related Chronic Liver Disease Death Example of county bar chart • McKinley county AR-CLD death rate: 39.3/100,000 • McKinley county deaths: 119/1,304 = 9.1% of AR-CLD statewide deaths • New Mexico AR-CLD death rate: 14.4/100,000 *All rates are per 100,000, age-adjusted to the 2000 US population

  29. How to use this reportRates and numbers • Example: McKinley and Bernalillo counties • Consider both prevalence and rate when designing interventions • County with highest alcohol-related death rate • 115.1 deaths / 100,000 population • County with highest proportion of alcohol-related deaths in the state • 1,491/ 5,068 = 29.5%

  30. Alcohol-Related Death Rates by County Example of county bar chart • McKinley county alcohol-related death rate: 115.1/100,000 • New Mexico • alcohol-related death rate: • 56.7/100,000 • Bernalillo county 1494/5,068 = 29.5% of AR-CLD statewide deaths *All rates are per 100,000, age-adjusted to the 2000 US population

  31. How to use this report ATODA consumption behaviors • BRFSS data estimate number and percent of people in population engaging in behavior • Table 1: Statewide estimates by age, sex, and race/ethnicity • Table 2: County estimates by race/ethnicity • County bar charts arranged in descending order

  32. Adult Drinking and Driving Rates by County Example of county bar chart: BRFSS • Luna county: 4.8% of adults reported drinking and driving at least once in past 30 days • No estimates available for small counties • Bernalillo county accounted for 47.8% of statewide drinking drivers *Estimate of percent of people in population group who drove after drinking at least once in previous 30 days

  33. How to use this reportATODA consumption behaviors • YRRS data estimate percent of public high school students engaging in behavior • Table 1: Prevalence estimates by grade, sex, and race/ethnicity • Chart 1: County bar charts with prevalence estimates arranged in descending order

  34. Drinking and Driving Rates by County, Grades 9-12 Example of county bar chart: YRRS • Union county: 35.7% of youth reported drinking and driving in the past 30 days • New Mexico: 19.1% of youth

  35. Survey Data • BRFSS • Telephone survey of adult health conditions and risk behaviors • Random sample of adults 18 years of age or older in households with a land-line telephone • Able to generate population-based estimates for adults • YRRS • School-based survey of health risk and resiliency behaviors among 9th-12th graders in NM • School districts must agree to participate • Estimates representative of public high school students • Both surveys include self-reported data

  36. Alcohol-Related MVC Death Rates by County Adult Drinking and Driving Rates by County

  37. How to use this report Missing data • Rates calculated using small numbers are unstable and difficult to interpret • Exclusions of rates occurred if: • Fewer than four deaths and population <20 in the rate denominator (NM standard small numbers rule) • Fewer than two deaths per county per year • Results in data gaps for certain groups

  38. NM standard small numbers rule Examples of cells affected by additional SPF-SIG rule

  39. Death Hospitalization Ambulatory Not reported in any system Data Collection • Think about data availability as a pyramid • Numerator – what are you counting? • Denominator – who is in the target population? • Are the data already available? • If not, can they be collected in a systematic way?

  40. Data Collection • Numerator: Counting DWI convictions in 2004 • Denominator: Determining the population at risk Example 1 – 2004 DWI Conviction Rate for New Mexico

  41. Example 1 2004 DWI Conviction Rate for NM Numerator = # of DWI convictions in NM in 2004 =12,639 Denominator = # of licensed drivers in NM in 2004 =1,289,089 Time Period = 2004 Constant = 1,000 DWI Conviction Rate NM 2004 = _12,639_ X 1,000 1,289,089 = 9.80/1,000 Source: New Mexico Department of Transportation, Driving While Impaired in NM, 2004 Report

  42. Data Collection Example 2 – Fetal Alcohol Syndrome (FAS) Rate in New Mexico • Numerator: Counting FAS cases in NM • Denominator: Determining the population at risk

  43. Diagnosis of FAS • Documentation of 3 dysmorphic facial features • Prenatal or postnatal growth deficit in height or weight • CNS abnormality • Diagnosis classified on the basis of available history of confirmed or unknown prenatal alcohol exposure

  44. Mothers Who Drank Alcohol Three Months Prior to Pregnancy and During the Last Three Months of PregnancyNew Mexico, 1998-2002 Source: Pregnancy Risk Assessment & Monitoring System (PRAMS), NMDOH

  45. Example 2 FAS Prevalence Rate in NM Numerator = # FAS-affected children born 1998-2002 Denominator = # live births in NM 1998-2002 Time Period = 1998-2002 Constant = 10,000

  46. Data Collection - Discussion • What are some other substance use consequences in your community? • Are there data already available? • If data need to be collected, how would you define a case/event (numerator) and the population at risk (denominator)? • Who can you call for help?

  47. Acknowledgments Dan Green, Social Indicator Epidemiologist Jim Roeber, Alcohol Epidemiologist Substance Abuse Epidemiology Unit Corazon Halasan, Community Epidemiologist Community Health Assessment Program

  48. Contact Information Tierney Murphy Substance Abuse Prevention Epidemiologist New Mexico Department of Health Phone: 827-6816 E-mail: tierney.murphy@state.nm.us

  49. Omitted Slides

  50. Data Collection Example 3 – School Truancy Rate in Your Community • Numerator: Counting middle and high school students who have unexcused absences • Denominator: Determining the population at risk

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