Background:
Smoking has been linked to low-grade systemic inflammation, a known risk factor for disease. This state is reflected in elevated white blood cell (WBC) count.

Objective:
We analyzed the relationship between WBC count and smoking in healthy men and women across several age ranges who underwent preventive medical check-ups in the workplace. We also analysed the relationship between smoking and lung function

Methods:
Cross-sectional descriptive study in 163 459 men and 59 382 women aged between 16 and 70 years. Data analysed were smoking status, WBC count, and spirometry readings.

Results:
Total WBC showed higher counts in both male and female smokers, around 1000 to 1300 cell/ml (t test, P < 0.001). Forced expiratory volume in 1 second (FEV1%) was higher in nonsmokers for both sexes between 25 to 54 years (t test, P < 0.001). Analysis of covariance showed a multiple variable effect of age, sex, smoking status, body mass index on WBC count. The relationship between WBC blood count and smoking status was confirmed after the sample was stratified for these variables. Smokers with airway obstruction measured by FEV1% were found to have higher WBC counts, in comparison to smokers with a normal FEV1% among similar age and BMI groups.

Conclusions:
Smoking increases WBC count and affects lung function. The effects are evident across a wide age range, underlining the importance of initiating preventive measures as soon as an individual begins to smoke.