The risk of myocardial infarction is enhanced by a synergistic interaction between serum insulin and smoking.
OBJECTIVE
To evaluate the relationship between levels of serum insulin, the homeostasis model assessment (HOMA) and IGF-binding protein-1 (IGFBP-1) as factors related to myocardial infarction (MI) risk, and their interaction with lifestyle-related risk factors.


METHODS
The Stockholm epidemiology programme (SHEEP), a case-control study, consisting of 749 first-time MI cases (510 men, 239 women) and 1101 healthy controls (705 men, 396 women) was used.


METHODS
The risk of developing MI was assessed by calculating odds ratios (OR) and synergistic interactions (SI) between serum insulin, IGFBP-1, HOMA and other variables related to MI risk (including smoking) in men and women.


RESULTS
Subjects with elevated levels of insulin and HOMA (>75th percentile) had increased MI risks when compared with individuals with low levels. ORs for elevated insulin and HOMA (adjusted for age and residential area) for men: insulin 1.6 (95% confidence interval (CI) 1.3-2.1) and HOMA 1.5 (95% CI 1.1-1.9) and for women: insulin 2.1 (95% CI 1.5-2.9) and HOMA 1.9 (95% CI 1.3-2.8). Women with low levels of IGFBP-1 (<10th percentile) showed a tendency towards elevated MI risk even if this was not statistically significant (OR 1.5 (95% CI 0.9-2.6)). Smokers with high levels of serum insulin had greatly increased MI risk (OR for men: 4.7 (95% CI 3.0-7.2) and OR for women: 8.1 (95% CI 4.5-14.8)). SI scores based upon these interactions were statistically significant.


CONCLUSIONS
These results might have preventive cardiovascular implications as they clearly suggest that subjects with insulin resistance are particularly susceptible to the hazards of smoking.
Bennet
Anna M
AM
Division of Cardiovascular Epidemiology, Karolinska Institute, Stockholm, Sweden. Anna.Bennet@imm.ki.se
Brismar
Kerstin
K
Hallqvist
Johan
J
Reuterwall
Christina
C
De Faire
Ulf
U
D016022:Case-Control Studies; D005260:Female; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000097:blood*; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000209:etiology*; D016017:Odds Ratio; D012307:Risk Factors; D012727:Sex Characteristics; D012907:Smoking / Q000009:adverse effects*
D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1