Hypothetical interventions and risk of myocardial infarction in a general population: application of the parametric g-formula in a longitudinal cohort study-the Tromsø Study

OBJECTIVES

The aim of this study was to use the parametric g-formula to estimate the 19-year risk of myocardial infarction (MI) under hypothetical interventions on six cardiovascular risk factors.

DESIGN AND SETTING

A populations-based cohort study with repeated measurements, the Tromsø Study.

PRIMARY OUTCOME MEASURE

Myocardial infarction.

PARTICIPANTS

We estimated the relative and absolute risk reduction under feasible and intensive risk reduction strategies for smoking, physical activity, alcohol drinking, body mass index, total serum cholesterol and systolic blood pressure in 14 965 men and women with 19 years of follow-up (1994-2013).

RESULTS

The estimated 19-year risk of MI under no intervention was 7.5% in individuals with baseline mean age 49.3 years (range 25-69). This risk was reduced by 30% (95% CI 19% to 39%) under joint feasible interventions on all risk factors, and 70% (60%, 78%) under a set of more intensive interventions. The most effective interventions were lowering of total cholesterol to 5.18 mmol/L and lowering of systolic blood pressure to 120 mm Hg (33% and 37% lower MI risk, respectively). The absolute risk reductions were significantly larger in men, in older participants, in smokers and in those with low education.

CONCLUSION

Modification of population levels of cardiovascular risk factors could have prevented close to one-third of the cases of MI in the municipality of Tromsø during 19 years of follow-up.

Temporal Trends in Incidence and Case Fatality of Intracerebral Hemorrhage: The Tromsø Study 1995-2012

Background

The aim of this study was to explore temporal trends in incidence and case fatality rates of intracerebral hemorrhage (ICH) over the last two decades in a Norwegian municipality.

Methods

Incident cases of primary ICH were registered in the period from 1995 through 2012 in 32,530 participants of the longitudinal population-based Tromsø Study. Poisson regression models were used to obtain incidence rates over time in age- and sex-adjusted and age- and sex-specific models. Case fatality rates were calculated and age- and sex-adjusted trends over time were estimated using logistic regression.

Results

A total of 226 ICHs were registered. The age- and sex-adjusted incidence rate [95% confidence interval (CI)] in the overall population was 0.42 (0.37-0.48) per 1,000 person-years. Age-adjusted incidence rates were 0.53 (0.43-0.62) in men and 0.33 (0.26-0.39) in women. In individuals aged <75 years, the age- and sex-adjusted incidence rate was 0.27 (0.22-0.32) and in individuals aged ≥75 years, it was 2.42 (1.95-2.89) per 1,000 person-years. There was no significant change in incidence rates over time. The incidence rate ratio (95% CI) in the overall population was 0.73 (0.47-1.12) in 2012 compared with 1995. The overall 30-day case fatality (95% CI) was 23.9% (18.3-29.5) and did not change substantially over time [odds ratio in 2012 vs. 1995 = 0.83 (95% CI 0.27-2.52)].

Conclusion

No significant changes in incidence and case fatality rates of ICH were observed during the last two decades.

Time Trends in Incidence and Case Fatality of Ischemic Stroke

Background and Purpose—

Ischemic stroke incidence has declined in industrialized countries the last decades, with possible exception for the youngest age groups. We estimated age- and sex-specific trends in incidence and case fatality of first-ever ischemic stroke between 1977 and 2010 in a Norwegian municipality.

Methods—

Age-adjusted time trends in incidence from 1977 to 2010 were estimated by fractional polynomial and Poisson regression, and case fatality by logistic regression in 36 575 participants of the population-based Tromsø Study.

Results—

There were 1214 first-ever ischemic strokes within a total follow-up time of 611 176 person-years. The overall age- and sex-adjusted incidence decreased by 24% in 1995 to 2010. In women aged 30 to 49 years, the incidence increased significantly from 1980 to 2010. In men aged 30 to 49 years, there was a nonsignificant, rising trend from 1977 to 2010. Men aged 50 to 64 years had similar incidence in 2010 compared with 1989. From the mid-1990s to 2010, the incidence declined significantly in women aged 50 to 74 years and in men aged 65 to 74 years, but remained stable in those aged ≥75 years. Case fatality decreased significantly in men aged 30 to 84 years from 1995 to 2010, whereas there was no significant change in women.

Conclusions—

Age-adjusted incidence of first-ever ischemic stroke increased in young women, declined in women aged 50 to 74 years and men aged 65 to 74 years and remained stable among the oldest. Case fatality declined in men aged 30 to 84 years, but not in women.