Accuracy of death certificates from diabetes, dementia and cancer in Australia: a population-based cohort study | BMC Public Health

Four notable findings emerged in the present study: (1) susceptibility to diabetes, dementia, and cancer being recorded as the underlying cause of death was low but improved significantly if contributing causes of death were taken into account; (2) women with dementia who died before 2006 were less likely to have dementia recorded on their death certificate, compared to those who died between 2006-2011 or 2012-2017. This trend was the opposite for diabetes and cancer; (3) Sociodemographic characteristics were weakly and inconsistently associated with the susceptibility of these conditions recorded on death certificates; and (4) diabetes and dementia were underreported, particularly on death certificates of women who died of circulatory disease or cancer.

In this study, we found that diabetes was recorded as the underlying cause of death for only 12.3% of women with diabetes during their lifetime. This was broadly consistent with the sensitivity seen in a US study of 11,927 diabetics (10%). [5] and another US study that used data from the National Mortality Follow-back Survey (NMFS) (10%) [12]but higher than the sensitivity found in the US Rancho Bernardo study (6.2%) [4]. The Rancho Bernardo study, which included 3,209 participants, found that the sensitivity of certification of death from diabetes was higher in women than in men, which may explain why the authors found lower sensitivity than ours, because our study had only women. . Whittal et al. investigated the accuracy of the diabetes death certificate in 1084 Caucasian subjects with diabetes who participated in surveys in rural Western Australia from 1978 to 1982, and found that 28% of these women had the diabetes recorded as underlying cause of death [13], which was much higher than our result seen in participants from Western Australia (13.4%). Whether this discrepancy indicates a downward trend in the accuracy of death certification from diabetes over the past decades in Western Australia warrants future investigation.

The accuracy of the dementia death certificate has been assessed in previous studies [6,7,8, 14,15,16,17,18,19,20]. We used survey data from a well-designed, nationally representative cohort study linked to multiple sources of routinely collected health data [21]. In our study, 52.3% of women with lifetime dementia had dementia recorded as an underlying or contributing cause of death, which was similar to the sensitivity seen in cohort studies in South London (53.6%). [7] and Finland (44.4%, 95% CI: 13.7, 78.8) [20]but higher than the sensitivity found in other cohort studies in England and Wales (21.0% in the Cognitive Function and Aging Study I (CFAS I)) [6]and the United States (28.4% and 23.8%) [14, 17]. The inconsistency between our results and the results of these studies could be due to the different periods studied. In the CFAS studies, the sensitivity of dementia death certification increased from 21.0% in participants recruited in 1989 (CFAS I) to 45.2% in participants recruited in 2008 (CFAS II) [6]. The inconsistency between the results of our study and the results of the American studies could also be explained by the different populations studied or the different gold standards used. Sensitivity of dementia death certification in US studies has generally been found to be low, even in people with end-stage dementia [16].

As the age range of participants in our study was narrow (i.e., five years), the difference in sensitivity of the dementia death certificate over the three time periods (i.e.,

Although diabetes is one of the strongest risk factors for cardiovascular disease, only 40.9% of women with diabetes had diabetes recorded as a cause of death in our study. We observed that diabetes was underreported, especially on the death certificates of women who died of ischemic heart disease. For these women, diabetes is unlikely to be unrelated to ischemic heart disease and not a contributing cause of death [13]. We also found that diabetes was underreported among women who died of cancer. This finding is consistent with that of a previous US study of 11,927 people with diabetes. [5]. Diabetes is increasingly recognized as a predictor of death from pancreatic, breast, liver and colon cancer [23, 24].

The reasons for the under-reporting of dementia on death certificates are manifold. First, cognitive impairment in people with dementia may prevent them from reporting symptoms and seeking medical help. [25], which may explain our finding that single women were less likely to have dementia recorded on their death certificate than women in a relationship. Second, the coexistence of more than one health problem (i.e. multimorbidity) is particularly common among older people. [26], making it difficult to identify dementia as the sole underlying cause of death, especially when dementia coexists with cardiovascular disease. Third, having dementia on a death certificate could be used to challenge the validity of someone’s will. [27]which may make the certifying physician less likely to record dementia as a cause of death.

It should be noted that the type of certifier (i.e. physician or coroner) also influences how multiple causes of death are recorded on death certificates. In Australia, deaths from natural causes (eg cancer or diabetes) are usually certified by a doctor, and most deaths from unknown or external causes (eg suicides) are certified by a coroner. About 86% to 89% of deaths are certified by a doctor [28], and multiple causes of death are more likely to be recorded for physician-certified deaths. Thus, multiple causes are more likely to be recorded for deaths related to diabetes, dementia and cancer than external causes. Previous analysis showed that this cohort was more socio-economically advantaged and had higher relative survival than other women in Australia born during the same period. [29]. However, the results presented in Figs. 1, 2 and 3 do not suggest that socioeconomic differences affected the sensitivity of cause of death recording.

Under-reporting of conditions on death certificates (e.g. diabetes, dementia or cancer) not only underestimates the burden of mortality associated with these diseases, but could also alter the underlying cause of death selected according to the coding rules in the automated processing. Several recommendations have been proposed to improve the accuracy of death certificates. First, as the current format of death certificates can have limited space, and it has been suggested that adding a series of checkboxes for the most common conditions to death certificates could improve the under-reporting of certain conditions (for example, diabetes) [30]. In Australia, electronic death certificate formats are being adopted in some States/Territories, allowing more conditions to be listed in Part II. Second, more educational support to help physicians improve the accuracy of death certificates could be helpful. Our findings underscore the importance of considering how causes of death (including underlying and contributing causes of death) are recorded, a challenge highlighted by the need to distinguish between death from COVID and death with COVID. In addition, national statistics showing both underlying and contributing causes of death would better represent the burden of disease.

Three main limitations of this study should be acknowledged. First, because this study was from the ALSWH, only women were included, which limits our ability to generalize the results to men. Second, the narrow age range of the participants limited the generalizability of the research findings to all women in Australia. Third, place of death (e.g., hospital or aged care facility) was found to be associated with death certificate accuracy for dementia [6, 7]but we were unable to obtain this information.

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