Data are presented in various ways within CK Public Health-Health Stats. Where applicable, numbers of “events” (deaths, hospitalizations, ED visits, cases) are provided for the most current year of data available, along with age-standardized, age-specific, and sex-specific rates. Any rates presented within text are followed by their associated 95% confidence interval in brackets (e.g. 271.9 (241.0, 302.8) per 100,000). For rates presented in bar chart format, associated 95% confidence intervals are noted visually through error bars. When comparing rates between sexes, across age groups, or between Chatham-Kent and Ontario, differences are noted when they are statistically significant. Below you will find key definitions to support interpretation of the information presented on this website.
The rate at which new events (new cases of a disease or health condition) occur in the population in the given time period (e.g. rate of new cases of lung cancer among the Chatham-Kent population).
The proportion of existing cases of disease or health condition at a particular time in a defined population (e.g percent of Chatham-Kent residents that currently smoke).
International Classification of Diseases and Related Health Problems 10th Revision (ICD-10)
Counts of hospitalizations, emergency department visits and deaths, to establish cause-specific rates are based on the International Classification of Diseases and Related Health Problems 10th Revision (ICD-10). The ICD is the foundation for the identification of health trends and statistics globally, and the international standard for reporting diseases and health conditions. Uses include monitoring of the incidence and prevalence of diseases, observing reimbursements and resource allocation trends, and keeping track of safety and quality guidelines. They also include the counting of deaths as well as diseases, injuries, symptoms, reasons for encounter, factors that influence health status, and external causes of disease. The ICD has undergone several periodic revisions over the years, which have been coordinated by the World Health Organization (WHO) since 1948. The ICD is currently in its tenth revision (ICD-10). The most current version of the ICD-10 is available on the WHO website – https://icd.who.int/browse10/2010/en
The ICD-10 has undergone some modification to meet the specific administrative, epidemiological and public health research requirements of Canadians (ICD-10-CA), and is wholly comparable with WHO ICD-10 classification. The ICD-10-CA is the classification recommended in most clinical settings and it is the national standard for reporting morbidity statistics.
A main diagnostic ICD code gives the primary reason for the hospital visit or “most responsible diagnosis” (MRDx). A second set of codes, external cause codes, are used to classify the environmental events, circumstances and conditions that cause injuries (e.g. motor vehicle injury, fall injury). While these external cause codes are the principal means for classifying injury deaths, they are not used as a MRDx for hospital visits so they need to be examined separately.
The crude rate represents the total number of “events” within a specific timeframe divided by the at-risk population (for example, the total population of Chatham-Kent within that specific year). While calculation of an overall crude rate helps to determine the burden of a health outcome within a population, crude rates are influenced by the underlying age distribution of the population; therefore, comparison of crude rates between two different populations (Chatham-Kent vs. Ontario) should be avoided.
The age-specific rate represents the crude rate except that the total number of “events” and the at-risk population is restricted to a specified age group (e.g. 45 to 64 year olds). Comparing age-specific rates allows conclusions to be drawn of whether certain age groups experience higher rates of a health outcome compared to others.
The age-standardized rate is a mathematically adjusted rate that assumes two different populations have the same age structure, thereby mitigating the influence of the underlying age distribution on the rate for both populations. The population used to age-adjust the rates is the 2011 Canadian Standard population.
Crude/Age-Standardized Rate Ratio
The crude/age-standardized rate ratio represents the crude/age-standardized rate of one population divided by the crude/age-standardized rate of another population (e.g. rate for Chatham-Kent divided by rate for Ontario). The result will provide a ratio of the two rates where conclusions can be drawn on whether the rates are higher, lower or similar and if this difference is statistically significant.
The 95% confidence interval (CI) indicates the reliability of a statistical estimate or rate. A 95% confidence interval is interpreted as a range in which we can be 95% confident the true population value lies. Wide confidence intervals, suggest less reliable estimates than narrow confidence intervals. In general, the larger the population, the narrower the CI and the more precise the estimate. Confidence intervals can also be used as tests of statistical significance when comparing estimates – if the CIs for the estimates under comparison overlap, we can say the difference between the estimates is not statistically significant. For CCHS data, 95% CIs have been calculated using the “bootstrap method”.
Statistically Significant Difference
A statistically significant difference is one that is considered “real” and not due to chance alone. Statistical tests can be performed to assess differences in estimates between groups, with the test of overlapping confidence intervals being one way to examine whether observed differences are statistically significant.