Interactive effects of obesity and physical fitness on risk of ischemic heart disease

Background/Objectives:Obesity and low physical fitness are known risk factors for ischemic heart disease (IHD), but their interactive effects are unclear. Elucidation of interactions between these common, modifiable risk factors may help inform more effective preventive strategies. We examined interactive effects of obesity, aerobic fitness and muscular strength in late adolescence on risk of IHD in adulthood in a large national cohort.Subjects/Methods:We conducted a national cohort study of all 1 547 407 military conscripts in Sweden during 1969-1997 (97-98% of all 18-year-old males each year). Aerobic fitness, muscular strength and body mass index (BMI) measurements were examined in relation to IHD identified from outpatient and inpatient diagnoses through 2012 (maximum age 62 years).Results:There were 38 142 men diagnosed with IHD in 39.7 million person years of follow-up. High BMI or low aerobic fitness (but not muscular strength) was associated with higher risk of IHD, adjusting for family history and socioeconomic factors. The combination of high BMI (overweight/obese vs normal) and low aerobic fitness (lowest vs highest tertile) was associated with highest IHD risk (incidence rate ratio, 3.11; 95% confidence interval (CI), 2.91-3.31; P<0.001). These exposures had no additive and a negative multiplicative interaction (that is, their combined effect was less than the product of their separate effects). Low aerobic fitness was a strong risk factor even among those with normal BMI.Conclusions:In this large cohort study, low aerobic fitness or high BMI at age 18 was associated with higher risk of IHD in adulthood, with a negative multiplicative interaction. Low aerobic fitness appeared to account for a similar number of IHD cases among those with normal vs high BMI (that is, no additive interaction). These findings suggest that interventions to prevent IHD should begin early in life and include not only weight control but aerobic fitness, even among persons of normal weight

Cardiorespiratory fitness and long-term risk of sleep apnea : A national cohort study

Sleep apnea is increasing in prevalence, and is an important cause of cardiometabolic diseases and mortality worldwide. Its only established modifiable risk factor is obesity; however, up to half of all sleep apnea cases may occur in non-obese persons, and hence there is a pressing need to identify other modifiable risk factors to facilitate more effective prevention. We sought to examine, for the first time, cardiorespiratory fitness in relation to the risk of sleep apnea, independent of obesity. A national cohort study was conducted to examine cardiorespiratory fitness in all 1,547,478 Swedish military conscripts during 1969–1997 (97%–98% of all 18-year-old men) in relation to risk of sleep apnea through 2012 (maximum age 62 years). Cardiorespiratory fitness was measured as maximal aerobic workload in Watts, and sleep apnea was identified from nationwide outpatient and inpatient diagnoses. A total of 44,612 (2.9%) men were diagnosed with sleep apnea in 43.7 million person-years of follow-up. Adjusting for age, height, weight, socioeconomic factors and family history of sleep apnea, low cardiorespiratory fitness at age 18 years was associated with a significantly increased risk of sleep apnea in adulthood (lowest versus highest cardiorespiratory fitness tertile: incidence rate ratio, 1.44; 95% confidence interval, 1.40–1.49; p < 0.001; continuous cardiorespiratory fitness per 100 Watts: incidence rate ratio, 0.71; 95% confidence interval, 0.70–0.73; p < 0.001). An increased risk was observed even among men with normal body mass index (lowest versus highest cardiorespiratory fitness tertile: incidence rate ratio, 1.30; 95% confidence interval, 1.26–1.35; p < 0.001). These findings identify low cardiorespiratory fitness early in life as a new modifiable risk factor for development of sleep apnea in adulthood

Interactive effects of physical fitness and body mass index on risk of stroke : A national cohort study

BACKGROUND: High body mass index (BMI) and low physical fitness are risk factors for stroke, but their interactive effects are unknown. Elucidation of interactions between these modifiable risk factors can help inform preventive interventions in susceptible subgroups.METHODS: National cohort study of all 1,547,294 military conscripts in Sweden during 1969-1997 (97-98% of all 18-year-old males). Standardized aerobic capacity, muscular strength, and body mass index measurements were examined in relation to stroke identified from inpatient and outpatient diagnoses through 2012 (maximum age 62 years).RESULTS: Sixteen thousand nine hundred seventy-nine men were diagnosed with stroke in 39.7 million person-years of follow-up. High body mass index, low aerobic fitness, and (less strongly) low muscular fitness were associated with higher risk of any stroke, ischemic stroke, and intracerebral hemorrhage, independently of family history and sociodemographic factors. High body mass index (overweight/obese vs. normal) and low aerobic capacity (lowest vs. highest tertile) had similar effect magnitudes, and their combination was associated with highest stroke risk (incidence rate ratio, 2.36; 95% CI, 2.14-2.60; P < 0.001). Aerobic capacity and muscular strength had a positive additive and multiplicative interaction (P < 0.001), indicating that low aerobic capacity accounted for more strokes among men with low compared with high muscular strength.CONCLUSIONS: High body mass index and low aerobic capacity in late adolescence are associated with increased risk of stroke in adulthood. Low aerobic capacity and low muscular strength also have a synergistic effect on stroke risk. These findings suggest that preventive interventions should include weight control and aerobic fitness early in life, and muscular fitness especially among those with low aerobic capacity