Mary Emmett, PhD, FACHE Center for Health Services and Outcomes Research

Transcription

1 Mary Emmett, PhD, FACHE Center for Health Services and Outcomes Research

2 Objectives Information to increase an understanding of common terms used in healthcare. To increase an understanding of how statistics are applied. To demonstrate skill in the application of statistics.

3 Prevention of falls in older people living in the community Prevalence Incidence Longitudinal Percentage Best available evidence Odds Ratio Confidence Interval Sensitivity Specificity F =; p

4 Prevention of falls in older people living in the community Predictive Non-linear Relative rate Relative risk Risk ratio Pooled relative risk Systematic Review Meta-Analysis Randomized controlled trial

5 Prevalence According to the WHO, 28-35% of older people (> 65 years) fall each year globally and prevalence increases with age. Prevalence = measure of how common a condition or disease occurs in the population. Expressed as a percentage. Incidence Incidence = rate of occurrence of new cases in a specified period of time. Usually it is one year. Expressed as a rate. E.g. the number of new falls in a year divided by the size of the population over the age of 65 who did not have a fall.

6 Longitudinal A longitudinal study found that 68% of people who fell reported some injury. What is meant by this term? Data are gathered on falls over an extended period of time, usually several years. If the data are from the same people it is called a longitudinal cohort study.

7 Best Available Evidence This review summarizes the best available evidence on risk factors for falls in older people living in the community and how to assess the risk of falls. What is the best available evidence? Best refers to valid and reliable information, which is the result of studies.

8 Sensitivity versus Specificity The timed up and go (TUG) test involves timing how long it takes some to get up from an armchair, walk 3 m, turn around, come back and sit on the same chair. The test is fairly easy to administer and takes less than 5 minutes. It has been shown to be a reliable and valid indicator of falls risk. In general, TUG times > 12 seconds are associated with an increased risk of falls. A study found that older adults who had a previous fall took 22 s (standard deviation 9) to complete the TUG, while non-fallers took 8 s (2) to complete the test (F=23; p<0.001). Using a cut-off value of 13.5 s, TUG had a sensitivity of 80% and a specificity of 100%.

9 Sensitivity Context timed up and go test. Using a cut-off value of 13.5 s, TUG has a sensitivity of 80% and specificity of 100%. Sensitivity = true positive TUG percentage. In this case the cut-off was positive 80% of the time. Specificity Specificity = the true negative percentage. In this case the % of persons not included was 100%. In other words, the cut-off was set high enough that no one was missed. Both terms are associated with TUG

10 TUG: Additional Terms Standard Deviation = 22 s with a std. deviation of 9. This means the variation in the sample. In this case it is 13 s to 31 s. F = 23 this is a statistical value known as the F Statistic. An example of an F statistic is the output when conducting a t-test. p < means the value of the older adults who had a previous fall 22 s (standard deviation 9) to complete the TUG, compared with non-fallers took 8 s (2) to complete the test (F=23; p<0.001) is statistically significant based on an F=23.

11 Reliable vs Valid Reliability measure of consistency. Can you get the same result time after time. Validity do the instruments measure what they are supposed to! Important to remember: An instrument can not be valid unless it is reliable.

12 Prospective Research Design: Types of Research Randomized Controlled Trial Individuals are randomly assigned to an intervention or control or different interventions. Might include blinding of the investigators. Non-Randomized Comparative Trial Assigned to intervention or control Followed prospectively to determine differences in outcome Prospective Cohort Exposed and unexposed groups Follow over time

13 Research Design: Additional Considerations Meta-Analysis A 2013 systematic review and meta-analysis of randomized controlled trials evaluated the effect of fall prevention exercise programs on fall related injuries in community dwelling older adults. Systematic Reviews A systematic review of randomized trials of intervention to reduce falls in older people living in the community What is the difference? SR = summary of carefully designed studies. A systematic review answers a defined research question by collecting and summarizing all empirical evidence that fits prespecified eligibility criteria. MA = Includes the data from the selected studies and completes an analysis. A meta-analysis is the use of statistical methods to summarize the results of these studies.

14 Reliable vs Valid Reliability measure of consistency. Can you get the same result time after time. Validity do the instruments measure what they are supposed to! Important to remember: An instrument can not be valid unless it is reliable.

15 Relative Rate a cluster randomized trial (842 households). reported that home modification reduced the rate of injuries from falls by 39% compared with a waiting list control group (relative rate 0.61, 0.1 to 0.91) Comparing resulting in an association. Relative Risk A meta-analysis found that combined vitamin D and calcium supplementation of institutionalized older people was associated with reduced risk of fractures (relative risk 0.71, 0.57 to 0.89). This was compared to community group (0.89, ) Probability.

16 In statistics and epidemiology, relative risk or risk ratio (RR) is the ratio of the probability of an event occurring (for example, developing a disease, being injured) in an exposed group to the probability of the event occurring in a comparison, non-exposed group.

17 Odds Ratio People with type 2 diabetes have an increased risk of falls compared with those without type 2 diabetes (odds ratio 2.0, 95% confidence interval 1.2 to 3.4) Odds Ratio measure of the effect of diabetes on falls. Confidence Interval If the OR is > 1 the control is better than the intervention. If the OR is < 1 the intervention is better than the control. Confidence Interval -- the level of uncertainty with respect to the effect as measured by the odds ratio.

18 Predictive and Non-linear Predictive the preferred walking speed is predictive of a wide range of adverse health outcomes, including falls. TUG Non-linear The association between walking speed and falls is non-linear, with a greater risk of outdoor falls among faster walkers, and greater risk of indoor falls among slow walkers.

19 CREDIT Vieira ER, Palmer RC, Chaves PHM. Prevention of falls in older people living in the community. BMJ 2016; 353:i1419.