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Research Christmas 2017: Natural Phenomena

Association between rainfall and diagnoses of joint or back pain: retrospective claims analysis

BMJ 2017; 359 doi: (Published 13 December 2017) Cite this as: BMJ 2017;359:j5326
  1. Anupam B Jena, Ruth L Newhouse associate professor of health care policy and medicine1,
  2. Andrew R Olenski, graduate student2,
  3. David Molitor, assistant professor of finance3,
  4. Nolan Miller, professor of finance and Julian Simon faculty fellow3
  1. 1Department of Health Care Policy, Harvard Medical School Boston, MA 02115, USA; Department of Medicine, Massachusetts General Hospital, Boston, MA, USA; National Bureau of Economic Research, Cambridge, MA, USA
  2. 2Department of Economics, Columbia University, New York, NY, USA
  3. 3Department of Finance, University of Illinois at Urbana-Champaign, Champaign, IL, USA
  1. Correspondence to: A B Jena jena{at}
  • Accepted 1 November 2017


Objective To study the relation between rainfall and outpatient visits for joint or back pain in a large patient population.

Design Observational study.

Setting US Medicare insurance claims data linked to rainfall data from US weather stations.

Participants 1 552 842 adults aged ≥65 years attending a total of 11 673 392 outpatient visits with a general internist during 2008-12.

Main outcome measures The proportion of outpatient visits for joint or back pain related conditions (rheumatoid arthritis, osteoarthritis, spondylosis, intervertebral disc disorders, and other non-traumatic joint disorders) was compared between rainy days and non-rainy days, adjusting for patient characteristics, chronic conditions, and geographic fixed effects (thereby comparing rates of joint or back pain related outpatient visits on rainy days versus non-rainy days within the same area).

Results Of the 11 673 392 outpatient visits by Medicare beneficiaries, 2 095 761 (18.0%) occurred on rainy days. In unadjusted and adjusted analyses, the difference in the proportion of patients with joint or back pain between rainy days and non-rainy days was significant (unadjusted, 6.23% v 6.42% of visits, P<0.001; adjusted, 6.35% v 6.39%, P=0.05), but the difference was in the opposite anticipated direction and was so small that it is unlikely to be clinically meaningful. No statistically significant relation was found between the proportion of claims for joint or back pain and the number of rainy days in the week of the outpatient visit. No relation was found among a subgroup of patients with rheumatoid arthritis.

Conclusion In a large analysis of older Americans insured by Medicare, no relation was found between rainfall and outpatient visits for joint or back pain. A relation may still exist, and therefore larger, more detailed data on disease severity and pain would be useful to support the validity of this commonly held belief.


  • Contributors: All authors contributed to the design and conduct of the study, data collection and management, analysis interpretation of the data; and preparation, review, or approval of the manuscript. ABJ supervised the study and is the guarantor. The research conducted was independent of any involvement from the sponsors of the study. Study sponsors were not involved in study design, data interpretation, writing, or the decision to submit the article for publication.

  • Funding: No funding.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at (available on request from the corresponding author) and declare: support provided by grants from the Office of the Director, National Institutes of Health (ABJ, NIH early independence award, grant 1DP5OD017897-01) and National Institute on Aging (NM and DM, grant R01AG053350); no financial relationships with any organizations that might have an interest in the submitted work in the previous 3 years; and no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: Not required.

  • Data sharing: No additional data available.

  • Transparency: The guarantor (ABJ) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies are disclosed.

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