Smoking in young women in Scotland and future burden of hospital admission and death: a nested cohort study

Background
Many women smoke, yet few longitudinal studies have examined the non-fatal burden of smoking in women.
Aim
To investigate smoking in young women, and hospital admission and death in Scotland; and to compare mortality risk with elsewhere in the UK.
Design and setting
Nested cohort study: Royal College of General Practitioners' Oral Contraception Study, UK.
Method
A total of 4121 women categorised by smoking habits and living in Scotland at recruitment (1968-1969) were followed until March 2009. Cox regression was used to investigate smoking and survival time; mortality from cancer, circulatory, or respiratory disease, and all other causes; and hospitalisation for any reason, and for specific reasons. The number and type of hospital admissions and bed-days were examined by smoking status. Life tables and Cox regression were used to compare the mortality risk of women living in Scotland with that of women living elsewhere.
Results
All-cause mortality was increased in women who smoked <15 cigarettes daily (adjusted hazard ratio = 1.99, 95% confidence interval [CI] = 1.74 to 2.27) and those who smoked ≥15 cigarettes daily (adjusted HR = 2.81, 95% CI = 2.47 to 3.20). Smoking any amount increased death from cancer, circulatory, respiratory, and other causes. Increased risk estimates were seen in one or both smoking groups for hospitalisation for any cause, and for several specific causes. More smokers than non-smokers were admitted to hospital, for four or more reasons, and had a longer total stay. The median survival age among smokers was lower in Scotland than elsewhere. Higher adjusted hazard ratios for mortality were found among smokers in Scotland.
Conclusion
This study provides a powerful reminder of the burden of smoking in young women. In the UK, harmful effects appear to be worse in smokers in Scotland.