Effects of smoking cessation on insulin and cardiovascular risk factors--a controlled study of 4 months' duration.

OBJECTIVES

To investigate the effects on serum lipids, plasma fibrinogen, plasma insulin, plasma C-peptide and blood glucose, of smoking cessation after 4 months. To develop a group-based smoking intervention programme in primary health care.

SETTING

Twenty health centres in primary health care in southern Sweden.

SUBJECTS

Four hundred habitual smokers (> 10 cigarettes per day-1, > 10 years), recruited by advertisement in local papers.

INTERVENTION

The smokers were randomized, after stratification for age and sex, to one intervention group (n = 200) and one control group (n = 200). The intervention group was offered supportive group sessions and free nicotine supplementation (patches, chewing gum).

MAIN OUTCOME MEASURES

All participants were investigated at the start and after 4 months (medical history, physical examination, laboratory evaluation). Blood samples were drawn for determination of glucose, insulin and C-peptide, both in the fasting state and during an oral glucose tolerance test (OGTT), and for measurement of lipoproteins, fibrinogen, nicotine and cotinine.

RESULTS

In the intervention group 98 of the subjects (48%) had quit smoking after 4 months. They were compared with the 156 subjects in the control group (91%) who were still daily smokers during the whole period. There were no significant differences in any variable between the two (total) experimental groups at baseline. Plasma nicotine and cotinine decreased (P < 0.001) in the intervention group following smoking cessation, and weight increased by 2.7 kg. In the intervention group HDL-cholesterol increased by 11% (P < 0.001), whereas HbA1c increased by 2% (P < 0.05) only in the control group. No changes occurred in levels of glucose, insulin, C-peptide and fibrinogen.

CONCLUSION

The smoking cessation programme had a success rate of almost 50% over 4 months. Smoking cessation was associated with a marked increase in HDL-cholesterol levels but did not affect glucose tolerance. A concomitant weight increase may have blunted any independent beneficial effect of smoking cessation on glucose metabolism.