The Canadian Forces Cancer and Mortality Study II: a longitudinal record-linkage study protocol.

BACKGROUND: Military service exposes personnel to unusual situations with unclear health-related implications, and to identify both immediate and delayed risks, part of health surveillance includes examination of mortality and cancer rates that extends beyond periods of military service. The main aim of the Canadian Forces Cancer and Mortality Study II (CFCAMS II) is to describe the mortality and cancer experience of Canadian Armed Forces personnel (serving and released; about 230 000 people), with the further aim of informing health promotion and prevention programs for serving personnel and services for veterans after they leave the military. METHODS: This protocol is for a retrospective cohort study of serving and released Canadian Armed Forces personnel who enrolled on or after Jan. 1, 1976 in the Regular Force or Class C of the Reserve Force. To create our cohort, we identified record-linkage methods as the most appropriate mechanism to study mortality and cancer in those with a history of Canadian military service. Statistics Canada will link the CFCAMS II cohort file to the Canadian Vital Statistics (Mortality) and Canadian Cancer Registry databases for outcomes up to Dec. 31, 2014. The linkage will be stored in their highly secure linkage environment. Statistical analyses will be broadly divided into mortality and cancer incidence. RESULTS: We will quantify mortality and cancer morbidity incidence and survival using multiple established methods, as well as age-period-cohort regression models to describe the relation between military service and mortality and cancer outcomes. INTERPRETATION: The findings will represent novel and sound evidence on the risks and protective factors of military life.

Linking the Canadian Community Health Survey and the Canadian Mortality Database: An enhanced data source for the study of mortality.

BACKGROUND: This study summarizes the linkage of the Canadian Community Health Survey (CCHS) and the Canadian Mortality Database (CMDB), which was performed to examine relationships between social determinants, health behaviours and mortality in the household population. DATA AND METHODS: The 2000/2001-to-2011 Canadian Community Health Surveys were linked to the 2000-to-2011 CMDB using probabilistic methods based on common identifiers (names, date of birth, postal code and sex) for eligible respondents (85%; n = 614,774). Mortality records from January 1, 2000 through December 31, 2011 for people aged 12 or older were eligible for linkage (n = 2.774 million). The linkage was enhanced with information from the Historical Tax Summary File. Quality assessment consisted of internal and external validation. Cox survival analysis (age-adjusted) was conducted to estimate hazard ratios (HRs) associated with selected health behaviours. RESULTS: Overall, 5.3% of eligible CCHS respondents linked to a mortality record; false positive and false negative rates were 0.04% and 2.43%, respectively. Linkage rates were higher among males (5.8%) and people aged 75 or older (20.2%), reflecting known mortality risks. Survival analyses confirmed elevated mortality risk associated with heavy (HR 2.36, CI 1.84, 2.89) and light smoking (HR 1.91, CI 1.52, 2.33), compared with not smoking; underweight and obesity, compared with normal and overweight; low fruit and vegetable consumption; and lack of physical activity. INTERPRETATION: Linking health behaviour information from the CCHS to mortality data from the CMDB allows for a greater understanding of modifiable determinants of mortality.

Linking 2006 Census and hospital data in Canada.

BACKGROUND: Record linkage is commonly used in health research to fill data gaps. This study summarizes the linkage of the 2006 Census of Population (excluding Quebec) to hospital data from the Discharge Abstract Database (DAD). DATA AND METHODS: Hierarchical deterministic exact matching was employed to link 2006 Census and DAD (2006/2007, 2007/2008 and 2008/2009) data, based on linkage keys derived from three variables common to both files-date of birth, postal code and sex. The full census file (short-form; 23.4 million) was used for record linkage; the 20% file (long-form; 4.65 million) representing the study cohort was used for validation. Linked files were compared across jurisdictions, years and other selected covariates in terms of eligibility for linkage, keys linked, and linkage and coverage rates. RESULTS: Overall, 80% of linkage keys identified in the DAD were linked to the 2006 Census. The percentage of long-form census respondents linked to at least one hospital record ranged between 5% and 8% across jurisdictions; linkage rates were higher among known high users of hospital services: older age groups, lower-income individuals, and Aboriginal people. In general, the linked census file represents the majority of hospital events that occurred during the study period. Coverage rates (weighted/unweighted) varied by geography and age group, with lower weighted rates for the territories and some younger age groups. INTERPRETATION: With hierarchical deterministic exact matching, census data can be linked to multiple years of DAD data. Incorporation of updated postal codes from tax files reduced linkage rate attrition over time. Lower coverage rates for the territories and younger age groups suggest that these populations may be underrepresented in the linked files.

Using personal health insurance numbers to link the Canadian Cancer Registry and the Discharge Abstract Database.

BACKGROUND: Linking cancer registry and administrative data can reveal health care use patterns among cancer patients. The Canadian Cancer Registry (CCR) contains personal health insurance numbers (HINs) that facilitate linkage to hospitalization information in the Discharge Abstract Database (DAD). DATA AND METHODS: Valid HINs, captured in the CCR or obtained through probabilistic linkages to provincial health insurance registries, were used to deterministically link prostate, female breast, colorectal and lung cancers diagnosed from 2005 through 2008 with the DAD for fiscal years 2004/2005 to 2010/2011. RESULTS: At least 98% of tumours diagnosed from 2005 through 2008 had valid HINs in the CCR or obtained through probabilistic linkages. For provinces submitting day surgeries to the DAD, linkage rates to at least one DAD record were higher for female breast (95.6% to 98.1%), colorectal (96.9% to 98.7%) and lung cancers (92.8% to 96.3%) than for prostate cancers (77.2% to 91.6%). Among linked records, agreement was high for sex (99% or more) and complete date of birth (97% or more); the likelihood of a consistent diagnosis in the CCR and on at least one linked DAD record was higher for female breast (86.8% to 97.2%), colorectal (94.6% to 97.7%) and lung cancers (90.3% to 95.5%) than for prostate cancers (77.4% to 87.8%). INTERPRETATION: Deterministically linking the CCR and DAD using personal HINs is a feasible and valid approach to obtaining hospitalization information about cancer patients.

Two approaches to linking census and hospital data.

BACKGROUND: This study compares registry and non-registry approaches to linking 2006 Census of Population data for Manitoba and Ontario to hospital data from the Discharge Abstract Database (DAD). DATA AND METHODS: Using a probabilistic linkage, the registry approach linked the census data to provincial health insurance registries, followed by a deterministic linkage to the DAD based on health insurance number (HIN). The non-registry approach used hierarchical deterministic exact matching based on three variables common to both files to link census data to the DAD. The approaches were compared in terms of linkage and coverage rates, sensitivity and specificity, and consistency of HINs on the linked records. RESULTS: Results of the registry and non-registry linkage approaches were similar. In Manitoba, 7% and 6% of census long-form respondents linked to the DAD with the registry and non-registry linkage approaches, respectively; in Ontario, the linkage rate was 5% for both approaches. With the registry approach, the linked census-DAD data represented 84% (weighted) of hospital admissions in the 2006/2007 DAD in both provinces, compared with 82% in Manitoba and Ontario with the non-registry approach. INTERPRETATION: In the absence of access to provincial health insurance registries with which census data can be linked, a non-registry approach can be used to create a research-quality dataset.