Aim
To assess to what extent incidence of CEs and death related to smoking, hypertension, hyperlipidemia and diabetes is modified by obesity in men.
Methods
The study cohort consisted of 22 025 men who at baseline were between 27 and 61 years old, without history of MI and stroke. Mean follow-up time was 17.7 years. BMI was divided into underweight (BMI <20.0 kg/m²), normal weight (BMI 20.0-24.9 kg/m²), overweight (25.0-29.9 kg/m²) and obese (30.0 kg/m²). Incidence of CE, total mortality, CVD mortality and non-CVD mortality was estimated in relation to BMI after adjustment for potential confounding factors. RRs for CE were also studied in subgroups of smokers and non-smokers with normal weight, overweight and obesity.
Furthermore, incidence of CE was studied in men without hypertension, hyperlipidemia or diabetes and in men exposed to one and 2 of these risk factors, respectively. Potential interactions between obesity and these risk factors were evaluated, calculating a SI.
Results
All studied CV risk factors except for smoking increased with BMI. A linear association was found between BMI and incidence of CE and a J-shaped association between BMI and all-cause mortality. The RR for a CE after adjustment for potential confounding factors was 1.18 (95% CI: 1.07 – 1.31) in overweight and 1.39 (95% CI:
1.17 – 1.65) in obese compared to normal weight men. The subgroup analysis showed that only 2 % of the obese men were exposed to both hypertension, hyperlipidemia,
diabetes and smoking, and 16 % of them had none of these risk factors. In the latter group the CV risk was not significantly increased (Fig 1). A positive interaction was found between obesity and smoking for incidence of CE, SI 1.39 (95% CI: 1.02-1.89).
Conclusions
Obesity is associated with an increased incidence of CE and death in men. The risk associated with obesity is substantially increased by exposure to other atherosclerotic risk factors, of which smoking seems to be the most important.
Figure 1. Multivariate adjusted RR of CE by smoking (non-smokers in open bars and smokers in filled bars) and by number (i.e. none, one or 2-3) of other CV risk factors (RF, i.e.
diabetes mellitus, hypertension and hyperlipidemia) in 22025 men with normal weight, overweight and obesity. Non-smoking men with normal weight and without diabetes mellitus, hyperlipidemia or hypertension served as the referent group. Covariates included age, heart rate, marital status, socio-economic position, leisure-time physical activity, self-reported health, history of angina pectoris, history of cancer, and history of problematic drinking behaviour.
Normal weight Overweight Obesity Normal weight Overweight Obesity Normal weight Overweight Obesity
No RF One RF 2-3 RF
No of men: 4405 4605 2205 1669 219 166 1484 1835 1570 1384 341 229 265 315 505 440 213 172 No of CE: 93 279 79 147 7 21 88 271 121 207 26 37 37 71 76 84 40 43
Paper II: Obesity and myocardial infarction – vulnerability related to occupational level and marital status. A 23-year follow-up of an urban male Swedish population
Aim
To explore whether there are differences in the vulnerability to CE and death associated with overweight and obesity between groups defined in terms of occupation and civil status in men.
Methods
The study cohort consisted of 20 099 men who at baseline were between 27 and 61 years old, without history of MI and stroke. Mean follow-up time was 17.7 years. BMI was divided into normal weight (BMI <25.0 kg/m²), overweight (25.0-29.9 kg/m²) and obese (30.0 kg/m²). Age-adjusted prevalence of obesity was determined in each category of cohabitation status and occupational level. RRs for all-cause mortality and incidence of CE were calculated in relation to BMI, cohabitation status and occupational level, and in subgroups of these three parameters, with three different models of adjustments. Potential interactions between obesity and cohabitation status and between obesity and occupational level were evaluated, using both SI and interaction term in the Cox model.
Results
Obesity was more prevalent in manual workers, self-employed and men living alone.
Manual work and living alone were factors associated with increased mortality and CVD risk. Obesity was associated with an increased risk for CE and death in each occupational group. Being single increased the risk associated with obesity. In stratified analyses, after adjustment for biological and lifestyle factors, the risk
Table 1. Adjusted incidence of coronary events in relation to body weight, level of occupation and civil status. CIVIL STATUS CohabitingLivingalone CORONARYEVENTS Occupational levelBMI category # No. of events (No. of men)Events/1000 person-yearsRR (95% CI) Model 1 † RR (95% CI) Model 2 ‡ No. of events (No. of men)Events/1000 person-yearsRR (95% CI) Model 1† RR (95% CI) Model 2 ‡ NW270 (4,700)3.17ReferentReferent48 (1,080)2.591.1 (0.8 - 1.4)1.1 (0.8 - 1.5) NMWOW228 (2,578)5.901.4 (1.2 - 1.7)1.1 (0.9 - 1.4)38 (447)5.041.7 (1.2 - 2.4)1.4 (1.01 - 2.0) OB32 (310)6.061.7 (1.2 - 2.4)1.2 (0.8 - 1.7)9 (75)6.982.8 (1.4 - 5.5)1.7 (0.9 - 3.4) NW58 (784)4.15ReferentReferent13 (178)4.061.1 (0.6 - 2.1)1.2 (0.7 - 2.2) SEOW37 (545)3.820.9 (0.6 - 1.4)0.8 (0.5 - 1.2)14 (115)6.891.9 (1.04 - 3.4)1.6 (0.9 - 2.8) OB10 (118)4.571.3 (0.7 - 2.6)0.9 (0.5 - 1.9)6 (19)21.555.6 (2.4 - 13.3)4.7 (1.9 - 11.4) NW270 (3,780)4.04ReferentReferent97 (1,292)4.471.2 (0.9 - 1.5)1.2 (0.9 - 1.5) MWOW239 (2,724)5.001.3 (1.07 - 1.5)1.1 (0.9 - 1.3)71 (714)5.781.6 (1.2 - 2.0)1.3 (0.9 - 1.7) OB56 (479)6.801.7 (1.3 - 2.3)1.1 (0.8 - 1.5)30 (161)12.013.0 (2.1 - 4.4)a 1.9 (1.3 - 2.8)a BMI, body mass index; RR, relative risk; CI, confidence interval, NMW, non-manualworker; SE, self-employed; MW, manual worker; NW, normal weight; OW, overweight; OB, obesity . † Covariates in model 1 included age,smoking habits, sedentary leisure-time physical activity and historyof problematic drinking behaviour. ‡ Covariates in model 2 included age, hypertension, diabetes, serum total cholesterol, triglycerides, smoking habits, sedentary leisure-time physical activity and history of problematic drinking behaviour.Cohabiting men with normal weight (NW) served as the referentgroup for each analysis. # Normal weight is defined as a BMI less than 25; overweight 25.0 to 29.9; and obesity, at least 30.0 kg/m2 . a indicates significantly different from all other groups in respectively occupational level. 32
Table 1. Adjusted incidence of coronary events in relation to body weight, level of occupation and civil status.
CIVIL STATUS
Cohabiting Living alone
CORONARY EVENTS Occupational
level
BMI category #
No. of events (No. of men)
Events/1000 person-years
RR (95% CI) Model 1 †
RR (95% CI) Model 2 ‡
No. of events (No. of men)
Events/1000 person-years
RR (95% CI) Model 1†
RR (95% CI) Model 2 ‡
NW 270 (4,700) 3.17 Referent Referent 48 (1,080) 2.59 1.1 (0.8 - 1.4) 1.1 (0.8 - 1.5)
NMW OW 228 (2,578) 5.90 1.4 (1.2 - 1.7) 1.1 (0.9 - 1.4) 38 (447) 5.04 1.7 (1.2 - 2.4) 1.4 (1.01 - 2.0)
OB 32 (310) 6.06 1.7 (1.2 - 2.4) 1.2 (0.8 - 1.7) 9 (75) 6.98 2.8 (1.4 - 5.5) 1.7 (0.9 - 3.4)
NW 58 (784) 4.15 Referent Referent 13 (178) 4.06 1.1 (0.6 - 2.1) 1.2 (0.7 - 2.2)
SE OW 37 (545) 3.82 0.9 (0.6 - 1.4) 0.8 (0.5 - 1.2) 14 (115) 6.89 1.9 (1.04 - 3.4) 1.6 (0.9 - 2.8)
OB 10 (118) 4.57 1.3 (0.7 - 2.6) 0.9 (0.5 - 1.9) 6 (19) 21.55 5.6 (2.4 - 13.3) 4.7 (1.9 - 11.4)
NW 270 (3,780) 4.04 Referent Referent 97 (1,292) 4.47 1.2 (0.9 - 1.5) 1.2 (0.9 - 1.5)
MW OW 239 (2,724) 5.00 1.3 (1.07 - 1.5) 1.1 (0.9 - 1.3) 71 (714) 5.78 1.6 (1.2 - 2.0) 1.3 (0.9 - 1.7)
OB 56 (479) 6.80 1.7 (1.3 - 2.3) 1.1 (0.8 - 1.5) 30 (161) 12.01 3.0 (2.1 - 4.4)a 1.9 (1.3 - 2.8)a BMI, body mass index; RR, relative risk; CI, confidence interval, NMW, non-manual worker; SE, self-employed; MW, manual worker; NW, normal weight; OW, overweight; OB, obesity . † Covariates in model 1 included age, smoking habits, sedentary leisure-time physical activity and history of problematic drinking behaviour. ‡ Covariates in model 2 included age, hypertension, diabetes, serum total cholesterol, triglycerides, smoking habits, sedentary leisure-time physical activity and history of problematic drinking behaviour. Cohabiting men with normal weight (NW) served as the referent group for each analysis.
# Normal weight is defined as a BMI less than 25; overweight 25.0 to 29.9; and obesity, at least 30.0 kg/m2. a indicates significantly different from all other groups in respectively occupational level.
associated with obesity was limited to those who were single and who either had a blue-collar job or were self-employed (Table 1). The multivariate-adjusted RR for CE and death in obese manual workers who were single was 1.91 (95% CI: 1.21–3.02) and 2.54 (95% CI: 1.74–3.69), respectively, compared to those who were cohabiting.
A positive interaction was found between obesity and living alone for incidence of CE (SI 3.33 [95% CI: 1.18-9.40]) and for mortality (SI 1.85 [95% CI: 1.13-3.20]). In the published paper, p-values for the statistical interaction term in the Cox model between obesity and being single after stratification for occupational level, were erroneously presented as blue-collar workers: p=0.033 and 0.057, respectively for CE and all-cause mortality (page 546 line 13), and for self-employed: p=0.017 and p=0.063, respectively for CE and all-cause mortality (page 546, line 14). The correct p-values were reversed, i.e. p=0.057 and p=0.063 for CE, and p=0.033 and p=0.017 for all-cause mortality.
Conclusions
Obesity is associated with single status and manual job in men. Adjusted for lifestyle and biological risk factors, the increased risk of CE and death for obese men with manual jobs was applicable only to those who were single. Being single significantly increases the CV risk associated with obesity.