According to WHO, 235 million people currently suffer from this illness. The underlying mechanism of asthma have been explained in various studies and revealed asthma as a chronic respiratory disease marked by type-2 inflammation, fundamentally the T helper Type 2 (TH2) lymphocyte overactivity in the airways, causing airway hyperresponsiveness.

The TH1 and TH2 cells have counterregulatory associations. Nevertheless, the relationship between asthma (a TH2-predominant condition) and the risk of systemic inflammatory diseases, for example, RA (a TH1 condition) is not well known. Therefore, this population-based case-control study was focused on determining whether asthma was related to elevated risks of incident RA among adults. This research study by Sheen YH and colleagues examined current incident RA cases and controls matched by age, sex, and registration year from the general population in Olmsted County (Minnesota) between January 2002 - December 2007. Using the predetermined asthma criteria, they implemented comprehensive medical record reviews to identify the asthma status. The incidence of a history of asthma before the index date was differentiated between cases and controls. To adapt to confounding factors, logistic regression models were helpful. Out of a total of 439 cases, 221 were RA cases and 218 controls. The RA cases had 156 (70.6%) females, 207 (93.7%) white, 53 (24.0%) had a history of asthma and the median age at the index date was 52.5 years. A total of 35 controls (16.1%) out of 218 had a history of asthma. Remarkable associations were observed between asthma and increased risks of RA (adjusted odds ratio, 1.74; 95% CI, 1.05-2.90; P = .03) after the adjustment for age, sex, body mass index, socioeconomic status, and comorbidity.

In spite of counterregulatory relationship between TH1 and TH2 cells, the asthma patients had a significantly higher risk of developing RA than healthy individuals.