Cigarette smoking and risk of subsequent use of antibacterials: a follow-up of 365,117 men and women.

OBJECTIVES Antibacterial prescribing is driving antibiotic resistance. We aimed to analyse whether smoking habits are associated with susceptibility to be prescribed antibacterials in primary care and to examine whether patients' smoking habits influence physicians' choice of therapy. METHODS Information on smoking habits from health surveys in 1985-99 was related to use of antibacterials 5-25 years later by linkage to the Norwegian Prescription Database. The study population included 365 117 men and women, 40-45 years old. Individuals likely to have chronic obstructive airway disease were excluded. Relative risk (RR) of being dispensed antibacterials for systemic use was calculated for five levels of smoking intensity with never smokers as reference. Adjustments were made for age, education, marital status, household size, body mass index and residence (rural/urban). RESULTS Fifty-six percent of the male and 69% of the female never smokers received at least one antibacterial prescription in the whole period, increasing to 68% and 82%, respectively, in heavy smokers (>19 cigarettes/day) (adjusted RR 1.17 and 1.16). The percentage receiving at least one antibacterial prescription every year was 0.5% in male and 1.9% in female never smokers, increasing to 1.1% and 4.0%, respectively, in heavy smokers (adjusted RR 2.07 and 1.89). The proportion of antibacterial users who were prescribed broad-spectrum antibacterials increased with increasing cigarette consumption. CONCLUSIONS Smoking habits influenced the usage of antibacterials years later with a dose-response relationship. Prescribers seem to acknowledge smoking as a risk factor for resistant bacteria since broad-spectrum antibacterials are more frequently prescribed to smokers than never smokers.