Introduction
Rheumatoid arthritis (RA) and gout are the two most common form of inflammatory arthritis associated with pain, functional impairment, reduced health-related quality of life, hospitalization, and increased mortality [
1,
2]. In 2015, RA and gout were ranked as the 30th and 61st leading cause of years lived with disability in Sweden, respectively [
3,
4]. In the recent decades, better health status, lower disease activity, increased remission rates, and improved survival for RA have been reported and attributed to improvement in the management of RA toward early and aggressive treatment with disease-modifying antirheumatic drugs [
5‐
7]. These improvements led to reductions in orthopedic surgeries and hospitalizations for RA in several countries [
8‐
11]. By contrast, studies reported persistent suboptimal management of gout [
12,
13] with no improvement in premature mortality gap and rise in health care visits over recent decade [
9,
10,
14‐
16]. Despite the rising burden of gout, to our knowledge, there is limited data on temporal trend in gout hospitalizations and its contrast with RA hospitalizations over recent decades. To address this, we estimated temporal trends in RA and gout hospitalizations and their regional disparities among people aged ≥ 20 years in Sweden from 1998 through 2015 using routinely collected data recorded in the Swedish National Patient Register.
Discussion
We found substantial decline in the absolute and relative burden of RA hospitalizations in Sweden during the recent two decades, whereas those for gout almost doubled at the same time. Due to these opposite trends, age-standardized hospitalization rate of gout surpassed the rate for RA in 2015. While there were statistically significant changes in the absolute regional disparity (declined for RA and rose for gout), there were no statistically significant trends in the relative regional disparities.
The declining trend in RA hospitalizations in our study is consistent with decreasing trends in orthopedic surgeries and hospitalizations for RA reported from different locations [
8‐
11,
19]. These reductions are mainly attributed to better management of RA including treating to target, early and more aggressive use of disease-modifying antirheumatic drugs, and introduction of biologic agents [
6,
9]. Although reductions in RA hospitalizations and hospital days imply decrease in RA hospitalization costs, this decrease likely indicates a shift in RA costs rather than reduction in RA total costs (i.e., reduction in hospitalization costs offset by rise in medication costs) [
6,
11,
19]. A previous study in Sweden reported that substantial decline in hospital admissions and hospital days for RA from 1990 to 2010 resulted in a marked reduction in share of hospitalization costs from total RA costs (from 15% in 1990 to 3% in 2010) [
11]. On the other hand, RA outpatient physician visits remained relatively unchanged and inflation-adjusted total costs for RA rose by 32% over the same period mainly due to the introduction of biologic drugs [
11].
In contrast to the decline in RA hospitalizations, our results showed that hospitalization rates for gout almost doubled over the study period. The rising trends in gout hospitalizations have been reported in several studies [
9,
10,
16,
20]. The increasing trend in gout hospitalizations in our study is consistent with marked increase in gout incidence in Sweden over the recent decade [
12]. While the role of obesity epidemic, increasing use of diuretics and aspirin, shifts in diet and lifestyle, and rising gout awareness should not be overlooked, the substantial rises in gout hospitalizations very likely reflect persistent suboptimal gout management, medication non-compliance, and poor adherence to current gout guidelines [
13,
20‐
23]. Two recent studies from western Sweden found that only a minority of gout patients receive urate lowering therapy (e.g., only 25% of hospitalized gout patients were on recommended urate lowering therapy preceding admission [
20,
23]). Considering that gout is a treatable disease, this suboptimal care implies that many of gout hospitalizations are potentially preventable (e.g., a study noted that 89% of hospitalizations with a primary diagnosis of gout were preventable [
24]). The observed rise in gout hospitalizations with no statistically significant changes in the average length of hospital stay have very likely led to rise in hospitalization costs for gout. Previous studies in Canada [
9] and USA [
10] suggested that doubled hospitalization rate for gout was associated with 125 and 68% rises in inflation-adjusted gout hospitalization costs per 100,000 people over time. A recent study in Western Sweden reported that hospitalization rate and inflation-adjusted total annual hospitalization costs for gout increased by 45 and 56%, respectively, between 2009 and 2012 [
20].
The regional disparities in RA and gout hospitalizations in our study are consistent with geographic variations in incidence, prevalence, and treatment of these conditions [
13,
25]. In addition, regional differences in clinical practice including adherence to treatment guidelines, in environmental exposures, in distribution of risk factors including lifestyle, in socioeconomic factors, and in cultural norms including attitudes toward sickness benefits might partially explain the regional disparities in RA and gout hospitalizations [
13,
25]. Furthermore, despite the presence of the national health insurance with universal access to health care in Sweden, possibility of regional differences in availability of rheumatology specialists, and in patients’ health-seeking behavior and health care utilization cannot be ruled out.
Simultaneous investigation of the two most common form of inflammatory arthritis, the use of national inpatient data spanned over about two decades, and assessing both absolute and relative burden of hospitalizations are the main strengths of our study. However, several limitations of our study should be acknowledged. Misdiagnosis and coding errors in administrative data, particularly potential variations by time and place, is of concern. While in overall the principal diagnosis for about 1% of hospital admissions in the NPR is missing, potential regional variation in missingness is another source of concern. Due to substantial variations in coverage and quality over time, we did not include specialized outpatient care (including day surgeries) and primary care visits. For example, while the data on specialized outpatient care are available since 2001, the proportion of specialized outpatient care visits with missing primary diagnosis dropped from 25 to 30% in early years to about 4% in 2016 (
http://www.socialstyrelsen.se) that complicates conducting a proper temporal trend analysis. This implies that only those patients with more severe conditions requiring hospital admission are included in the study and hence generalizability of the findings to less severe health care visits is limited.
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