Do inhaled corticosteroids for asthma increase diabetes risk?

Oral corticosteroids such as prednisone have well-known side effects that include increased insulin resistance and risk for diabetes, but what if they are inhaled for chronic inflammatory respiratory conditions such as asthma? A study recently published in The American Journal of Medicine addresses this question. The authors first observe:

"Systemic corticosteroids are known to increase diabetes risk, but the effects of high-dose inhaled corticosteroids are unknown. We assessed whether the use and dose of inhaled corticosteroids increase the risk of diabetes onset and progression."

The authors examined a cohort of 388,584 patients treated for respiratory disease during 1990-2005, then followed them through 2007 or until diabetes onset. (A subcohort treated with oral blood sugar lowering medication was followed until they developed diabetes.) They evaluated their data to estimate the rate ratios of diabetes onset and progression associated with 'current' inhaled corticosteroid use and adjusted for the relevant variables. Their data showed that among their study cohort...

"...30,167 had diabetes onset during 5.5 years of follow-up (incidence rate 14.2/1000/year), and 2099 subsequently progressed from oral hypoglycemic treatment to insulin (incidence rate 19.8/1000/year). Current use of inhaled corticosteroids was associated with a 34% increase in the rate of diabetes and in the rate of diabetes progression. The risk increases were greatest with the highest inhaled corticosteroid doses, equivalent to fluticasone 1000 μg per day or more."

The authors' conclusion should be considered not only for the case management of asthma (before significant markers for pre-diabetes and diabetes emerge), but for the metabolic and endocrine effects beyond respiratory disease:

"In patients with respiratory disease, inhaled corticosteroid use is associated with modest increases in the risks of diabetes onset and diabetes progression. The risks are more pronounced at the higher doses currently prescribed in the treatment of chronic obstructive pulmonary disease."