Background/Purpose: Classical statistics provide information on mortality rates for basic causes of death. Although many inflammatory rheumatic diseases decrease life expectancy, they are generally not a direct cause of death. Since 2016, the Spanish Institute of Statistics provides information on all causes appearing on certificates, in addition to the basic one; this may help to estimate the real burden of this group of diseases on mortality in Spain.

Methods: Population estimates and individual death records for inflammatory rheumatic diseases [ICD10 M05-14; M30-36; M45-46] for 2016-2018 were available from the National Institute of Statistics. We calculated age-adjusted mortality rates by sex and by age group (0-44, 45-64 and ≥ 65) a) using only the basic cause (BC) (Table 1); and b) using the certificates in which these diseases appear anywhere, either as a basic, immediate, intermediate or fundamental cause (MCD) (Table 1). In the latter case, we also describe which are the non-rheumatic basic causes of death in the certificates mentioning rheumatic pathology (Figure1).

Results: Inflammatory rheumatic syndromes appeared in 6998 death certificates (2333 annual average, 63% women), although BC were considered in only 36% of them (833 deaths per year; 66% women), with age-adjusted mortality rates for MDC and BC of 1.56 and 0.64 deaths/100,000 inhabitants, respectively. In the certificates mentioning rheumatic pathology (MCD) in which this was not the basic cause, death was mainly attributed to cardiovascular disease (20%), cancer (12%) and respiratory diseases (10%).

Within age groups, the adjusted rate of MDC for deaths in those under 45 years of age was 0.17 per 100,000 (0.12 as a basic cause); 1.76 for the 45 to 64 range (0.85 as a basic cause); and 17.54 for those over 64 years of age (6.14 as a basic cause). Overall, the rates in women were somewhat higher, although the main differences between sexes were observed in systemic sclerosis and lupus (almost three times more frequent in women) and in spondyloarthritis (in which the male rates were double those of women). Rheumatoid arthritis, as expected, had the highest mortality in both sexes, with adjusted rates based on MDC more than three times higher than those calculated with BC alone (MDC: 0.56/100,000; BC: 0.17/100,000). The change in rates using MDC is rather less marked in the more aggressive entities, such as systemic sclerosis or systemic lupus erythematosus, and especially in deaths in persons younger than 45 years. In these subgroups, rheumatologic diseases are the basic cause of death in almost two thirds of the certificates in which they appear, and in almost 90% if we are talking about deaths in young people with systemic sclerosis.

Conclusion: At the population level, these syndromes have a non-negligible importance in terms of mortality, which is underestimated in the classic mortality statistics, based only on basic causes. The underestimation is less in the more severe rheumatologic processes. The rates provided here probably portray a picture closer to reality of the burden that these diseases represent in Spanish mortality.

Figure 1. Basic cause of death among deceases registering inflammatory rheumatic diseases in the death certificate. Spain, 2016_2018.

Table 1.Age-adjusted mortality rates in Spain in 2016_18 for all inflammatory rheumatic syndromes using MCD and BC approaches

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/estimating-the-weight-of-rheumatologic-diseases-in-mortality-in-spain-basic-cause-of-death-vs-multiple-cause-analysis/