Influence of environmental humidity on clinical and functional features of the course of asthma

Introduction. Previously it was shown that patients suffering from chronic obstructive pulmonary diseases are especially sensitive to changes in weather and climate conditions, in particular to one of the main meteorological elements - relative air humidity. At the same time, there is insufficient information on whether increased relative humidity can trigger the formation of osmotic airway hyperresponsiveness in patients with asthma and its features in different seasons of the year.

Aim. To study the clinical picture of the disease, lung function and the airway reaction to the hypotonic stimulus in asthma patients in seasons of the year which are contrasting in humidity.

Materials and methods. In 82 patients (average age 40.5±1.1 years) with mild persistent asthma, disease control was assessed using the ACT questionnaire. Lung function and airway response (AFEV₁) to 3-minute inhalation of ultrasonically nebulized distilled water (UNDW) were studied in the seasons of the year with low and high relative humidity of atmospheric air.

Results. In the initial examination of patients in a season with low relative humidity of ambient air, FEV₁ for the general group was 98.2±2.2%, MEF_25-75 72.9±3.5%, AFEV₁ -3.7±1.0%, ACT 18.3±0.6 points. Airway hyperresponsiveness to the hypoosmolar stimulus was detected in 12 (15%) patients (ΔFEV₁ -18.1±2.1%), 7 (9%) showed an increase in FEV₁ after UNDV by 12.1±3.3%, 63 (77%) patients did not have a reaction to UNDW (ΔFEV₁ -2.7±0.5%). When re-examining the same patients in the wet season, the lung function impairment was recorded (FEV1 averaged 93.8±2.3, p=0.023; MEF_25-75 6 3.9±3.3, р=0,006), airway reaction the UNDW was increased (ΔFEV₁ -8.1±1.4%, p=0.005), asthma control was decreased (ACT 17.0±0.7 points, p=0.034), the number of patients with altered reactivity to UNDW increased from 23 to 50%. In the wet season, the number of asthma patients with osmotic airway hyperresponsiveness (ΔFEV₁ -19.8±1.9%) reached 40% (33 patients) (χ²=12.3; p<0.001), 8 (10%) were observed with increase in FEV1 to the UNDW (9.4±1.4%), in 41 patients (50%) there was no airway reaction to the UNDV (ΔFEV₁ -2.0±0.7%).

Conclusion. An increase in the environment relative humidity in asthma patients leads to a decrease in control of the disease, worsening of airway patency, an increase in the severity of the airway reaction to acute bronchoprovocation with UNDW, and increase in the number of patients responding to the osmotic stimulus.

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