Higher resting heart rate in men 50 years old associated with higher CV risk in next 20 years
Impact of changes in heart rate with age on all-cause death and cardiovascular events in 50-year-old men from the general population
Introduction and methods
Multiple studies have demonstrated an association between elevated resting heart rate (RHR) and a higher incidence of CV diseases, all-cause and CV mortality in the general population. The risk for CV morbidity and mortality increases in middle age, and RHR also changes with age.
The impact of the incremental change in RHR on incident CV morbidity and mortality in middle-aged general populations is unknown. This study therefore set out to assess the impact of RHR at baseline and the change in RHR over time on the risk of CV morbidity and mortality in middle-aged men, enrolled in ‘the study of men born in 1943’ . This is a longitudinal, prospective, population-based study of men born in 1943 and living in the city of Gothenburg in Sweden when they were 50 years old.
A random sample of 50% of men qualifying for these criteria were invited (n=1450) in 1993, of whom 798 (55%) accepted to participate. At the second examination in 2003, 749 were still alive, of whom 654 agreed to be re-examined. At the third examination in 2014, 536 of 688 men still alive accepted to be re-examined. At each examination visit, medical history was obtained and a physical examination performed. During the 2014 visit an echocardiogram was made. Fasting venous blood samples were taken to determine plasma levels of total serum cholesterol, triglycerides, creatinine, HDL, NT-pro-BNP and IL-6. Questionnaires were used to get information on smoking habits, physical activity and family history of CVD, previous disease and mental stress.
RHR was measured with 12-lead ECG in supine position at each visit. The study sample was divided into four subgroups based on RHR in 1993: 1: RHR <55 beats per minute (bpm), 2: RHR 56-65 bpm, 3: 66-75 bpm and 4: RHR >75 bpm. Change in RHR (ΔHR) was calculated by subtracting RHR of 1993 from RHR in 2003. Three subgroups were then created according to ΔHR: 1: decreased RHR: ΔHR ≤-5bpm, stable RHR: -5bpm < ΔHR < 5 bpm and increased RHR: ΔHR ≥ 5 bpm. Outcome variables were all-cause mortality, CVD and coronary heart disease (CHD).
- Average RHR was lower in 2003 (61±10 bpm) than in 1993 (67±12 bpm) and remained unchanged in 2014 as compared with 2003. At the second and third visit, fewer participants had RHR >75 bpm (2003: 11.2% and 2014: 11.2%) compared with baseline (24.1%). More participants had RHR ≤55 bpm in 2003 (29.2%) and 2014 (26.3%) than in 1993 (13.7%).
- When looking at subgroups based on baseline RHR, those with high RHR (>75) showed the highest incidence of all-cause death (HR-adjusted [HRadj]: 2.34, 95%CI: 1.16 to 4.74, P=0.018), CVD (HRadj: 1.82, 95%CI: 1.13 to 2.95, P=0.014) and CHD (HRadj: 2.24, 95%CI: 1.11 to 4.54, P=0.025). Risk in the intermediate RHR categories did not significantly differ from that in the lowest group.
- When analyzing RHR as a continuous variable, every increase in beat in RHR after 1993 was associated with a 3% higher risk of all-cause death (HR: 1.03, 95%CI: 1.01-1.04, P<0.001), a 1% higher risk for CVD (95%CI: 1.00-1.02, P=0.027) and a 2% higher risk for CHD (95%CI: 1.01-1.04, P=0.008). Higher RHR from 2003 onwards increased only the risk of all-cause death.
- In 2003, 111 of 654 men had increased RHR as compared with 1993, 205 had relatively unchanged RHR and 338 had a decreased RHR.
- Those with stable RHR from 1993 to 2003 had 44% lower risk of CVD (HRadj: 0.56, 95%CI: 0.35-0.87< P=0.011) compared with those with increased RHR.
- Those with decreased RHR did not show a significantly different risk of CVD compared with those with increased RHR (HRadj: 0.91, 95%CI: 0.61-1.34, P=0.622).
In men born in 1943 from the general population, baseline RHR in 1993 was an independent risk factor of all-cause death, CVD and CHD over a follow-up period of 21 years. Moreover, an increase in RHR between 50 and 60 years of age was associated with a higher risk of CVD compared with individuals with stable RHR. No significant difference was seen in CVD risk between those with increased and decreased RHR over time.