Background and objective: Although smoking is associated with an increased incidence of cardiovascular disease and death, many smokers remain healthy after many years of smoking. Our objective was to assess whether this variation is related to rate of decline of respiratory function.
Design: This was a population-based cohort study, its subjects being men born in 1914 from Malmö, Sweden.
Methods: All 291 smokers who since the baseline examination in 1969 had remained in Malmö were invited to a follow-up examination in 1982. Of the 242 participants, 199 men without history of myocardial infarction or stroke were included in the study. Eighty-four of them had quit smoking. The incidence of cardiovascular disease and death during 14 years was studied in relation to the decline in lung function [forced expiratory volume during 1 second (FEV1.0) and vital capacity] between 55 and 68 years of age.
Results: Fifty-nine (51%) smokers and 43 (51%) ex-smokers died. Forty-four (38%) smokers and 29 (35%) ex-smokers suffered a cardiovascular event. The mortality rate among smokers in the high, middle and low thirds with regard to the decline in FEV1.0 was 66.5, 44.0, and 37.6, respectively, per 1000 person-years (P for trend = 0.04). The corresponding figures in ex-smokers were 88.7, 42.0, and 35.1 (P for trend = 0.002). The cardiovascular event rate among smokers in these three groups was 56.0, 41.0, and 22.7 events, respectively, per 1000 person-years (P for trend = 0.01). The association remained significant after adjustments for potential confounders. A change in vital capacity was associated with a similar pattern of disease and death.
Conclusion: Although smoking is associated with an accelerated respiratory decline, there are marked differences between smokers. The increased cardiovascular event and death rates among those whose lung function declined the most suggests that the change in respiratory function can be used as a measure of individual susceptibility.