Background/Purpose: Most studies looking at seasonal variations in giant cell arteritis (GCA) note a seasonal trend, but show disparity on timing. Concurrent peaks of GCA and polymyalgia rheumatica (PMR) have been described by some studies questioning a common precipitating agent. We aimed to analyze the seasonal variation of GCA and PMR in the US using a large inpatient database.

Methods: We used Nationwide Inpatient Sample (NIS) database to identify patients aged ≥ 18 years from 2009-11 with a diagnosis of GCA and PMR with ICD-9-CM codes 446.5 and 725 in the first 3 positions. We used the Edwards’ recognition and estimation of cyclic trend method to study the seasonal patterns of GCA and PMR hospitations stratified by age. Z-test was used to compare seasonal incidences

Results:

A total of 57728 and 242862 hospitalizations with a diagnosis of GCA and PMR respectively were reported from 2009-11. A significant seasonal variation was observed with highest number of GCA hospitalizations in summer (peak/low ratio 1.092, 95% CI 1.067-1.118, p<0.0001) and most significant peaks seen in age group 65-69 (peak/low ratio 1.092, 95% CI 1.067-1.118, p<0.0001) (Figure 1). No significant seasonal variation was seen with PMR hospitalizations.

Conclusion:

Our study found peak GCA hospitalizations in summer months which is concurrent with trends seen in Israel and England but differ from other studies showing peaks in late winter and autumn. Interestingly, no similar pattern was observed in closely related disorder, PMR. A better understanding of these patterns could lead to identification and possibly control of potential environmental triggers in the genetically predisposed population.

Figure 1. Graph showing seasonal trend for GCA and PMR, 2009-2011

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/seasonal-variation-in-giant-cell-arteritis-and-polymyalgia-rheumatica-hospitalizations-data-from-nationwide-inpatient-sample/