Using subjective and objective measures to estimate respiratory health in a population of working older Kentucky farmers, Part 2.

Transcription

1 Using subjective and objective measures to estimate respiratory health in a population of working older Kentucky farmers, Part 2. Reliability of symptom report in older farmers Nancy E. Johnson, DrPH, CIH University of Kentucky College of Public Health

2 Study Objective Over 20% (n=29) of working older farmers in a convenience-scheduled screening exam had an FEV1% < Less than a third knew they had asthma. Over half reported no respiratory symptoms in the past year. Evaluation of specificity and sensitivity of respiratory symptom questions in estimating disease prevalence for this population AIHce Philadelphia, PA 2

3 Older Farmers Don t Quit It is not uncommon for older American farmers to work well past the traditional industrial retirement age The ability to work is a prime measure of health Continue farm work despite chronic illness or disability over the perceived uselessness of retirement. AIHce Philadelphia, PA 3

4 Methods Used data from Older Farmer Cohort (n=134) derived from the Kentucky FFHHSP. Frequencies and predictive statistical analysis SAS version 8.2 software. Symptom specificity and sensitivity with regard to the accuracy of screening questions in predicting respiratory outcomes of self-reported asthma and objective decline in lung function. EpiInfo, version 6 AIHce Philadelphia, PA 4

5 Definitions to keep in mind... Sensitivity is the probability that a symptom is positive if the person has the measured outcome (true positive) Specificity is the probability that a person without the measured outcome will not have that symptom (true negative) Positive predictive value is the probability that the person has a selected outcome given a positive test result. AIHce Philadelphia, PA 5

6 Table 3. Sensitivity and Specificity of Screening Questions Self-report of physician-diagnosed asthma Screening question No asthma Asthma Predictive value Sensitivity + - (95% CI) Wheeze in past 12 m Yes No 92 4 ( ) Wheeze w/o cold Yes No 97 9 ( ) Chest tight at work Yes No 98 9 ( ) Short of breath/hurry Yes No 65 2 ( ) Phlegm most days Yes No ( ) Good excel health Yes No 45 3 ( ) Spirometry Screening question Normal FEV 1% < 80% Predictive Sensitivity value (95% CI) + - Wheeze in past 12m Yes No ( ) Wheeze w/o cold Yes No ( ) Chest tight at work Yes No ( ) Short of breath/hurry Yes No ( ) Phlegm most days Yes No ( ) Good - excellent health Yes No ( ) Specificity (95% CI) 0.81 ( ) 0.87 ( ) 0.88 ( ) 0.57 ( ) 0.85 ( ) 0.39 ( ) Specificity (95% CI) 0.77 ( ) 0.85 ( ) 0.85 ( ) 0.55 ( ) 0.85 ( ) 0.36 ( ) AIHce Philadelphia, PA 6

7 Table 4. Multiple logistic regression Variable Odds Ratio 95% Confidence Interval Mantel-Haenszel Χ 2 Related to self-report of asthma FEV 1% < Not significant Wheeze in the past 12 months ( ) * Chest wheeze without cold ( ) not significant Short of breath when hurrying ( ) * Stuffy nose ( not significant Smoking Status Never smoker Former smoker ( ) Current smoker ( ) Work Status Fully retired Partial or full-time work ( ) Related to FEV 1% < 0.80 Physician-diagnosed asthma ( ) Wheeze in the past 12 months ( ) Chest wheeze without a cold ( ) Short of breath when hurrying Stuffy nose ( ) Smoking status Never smoker Former smoker ( ) Current smoker ( ) Work Status Fully retired n.s. Partial or full-time work n.s. AIHce Philadelphia, PA 7 *significant p<0.05

8 FFHHSP Author State Farmers Current smokers Former smokers Non-smokers No. Average Age Wilkins, et al 1999 OH y % % % Sprince, et al 2000 IA y 51 13% % % Gomez, et al 2004 NY y % % % Champney, et al 1996 CO y 20 8% 62 27% % Johnson, et al 2007 KY y 19 14% 64 48% 51 38% AIHce Philadelphia, PA 8

9 Conclusions Respiratory symptom screening questions did not match objective measures of disease. The most sensitive screening questions associated with either physician-diagnosed asthma or low FEV1% was a positive response to the question Do you consider yourself to be in good to excellent health? Lack of response to certain screening questions age lower education levels, or regional dialect differences. The Kentucky cohort was older and less educated than the cohorts used for FFHHSP studies in other states. AIHce Philadelphia, PA 9

10 Is it the smoking? While only 20% of lifelong smokers ever develop chronic obstructive pulmonary disease, it has been estimated that half the elderly individuals with asthma have not been diagnosed despite the negative impact on their quality of life AIHce Philadelphia, PA 10

11 Conclusions No significant demographic variables predictive for decreased respiratory health. type of farming, age category, body mass index, farm activity level, work status, and education The more significant information, from a public health point of view, is that 25-40% of older Kentucky farmers who do not presently smoke either report symptoms related to respiratory disease or have objective decline in FEV1%. AIHce Philadelphia, PA 11

12 Conclusions Customary symptom questions did not reliably reflect objective indicators in the Kentucky older farmer cohort. Survey questions typically used to identify potential asthma were not particularly sensitive (but were relatively specific >80%) <30% when compared with FEV1% < 0.80 <50% when addressed to farmers who report a physician diagnosis of asthma. AIHce Philadelphia, PA 12

13 The Kentucky older farmer cohort demonstrates the problem of reliability for cross-sectional surveys which rely on interview questions for exposure markers like respiratory symptoms -- particularly in populations where status, such as senescence, and attitudes, such as high motivation to work, or other factors might complicate responses. AIHce Philadelphia, PA 13