Childhood growth patterns and cardiovascular autonomic modulation in midlife: Northern Finland 1966 Birth Cohort Study.

OBJECTIVES: To test the hypothesis that age and body mass index (BMI) at BMI peak during infancy and at BMI rebound in childhood are related to cardiovascular autonomic modulation in adulthood. METHODS: At the age of 46 years, a sample (n = 5861) of the participants of the Northern Finland Birth Cohort 1966 took part in follow-up examinations. Heart rate variability (HRV), baroreflex sensitivity (BRS) and low-frequency oscillations of systolic blood pressure (LFSBP) were measured during sympathetic stimulus by standing. BMI at various ages was calculated from frequent anthropometric measurements collected from child welfare clinical records. BRS and LFSBP were available for 1243 participants with BMI peak data and 1524 participants with BMI rebound data, and HRV for 2137 participants with BMI peak data and 2688 participants with BMI rebound data. RESULTS: Age at BMI rebound had a significant inverse association with LFSBP (beta = -0.071, p = 0.006) after all adjustments (p < 0.001) and was also directly associated with BRS (beta = 0.082, p = 0.001) independently of birth and maternal factors (p = 0.023). BMI at BMI peak and at BMI rebound was inversely associated with high-frequency component of HRV (HF) (beta = -0.045, p = 0.036 for BMI at peak; beta = -0.043, p = 0.024 for BMI at rebound) and directly associated with the ratio of low- and high-frequency components of HRV (LF/HF ratio) (beta = 0.084, p = < 0.001 for BMI at peak; beta = 0.069, p < 0.001 for BMI at rebound). These associations remained significant after all adjustments (p < 0.05 for all). CONCLUSIONS: This novel study shows that younger age at BMI rebound and higher BMI at BMI peak and at BMI rebound are associated with higher levels in markers suggestive of augmented sympathetic and reduced vagal cardiovascular modulation in midlife.

Fitness, Fatness, Physical Activity, and Autonomic Function in Midlife.

PURPOSE: Although low cardiorespiratory fitness (CRF), physical inactivity, and obesity are associated with impaired autonomic function, they are also extensively interrelated. The present study aimed to assess the extent to which they contribute to autonomic function independently of each other. METHODS: At the age of 46 yr, 1383 men and 1761 women without cardiorespiratory diseases and diabetes underwent assessments of vagally mediated heart rate (HR) variability (root mean square of successive differences in R-R interval (rMMSD)), peak HR during a submaximal step test (CRF), and 60-s HR recovery (HRR). Moderate-to-vigorous physical activity (MVPA; ≥3.5 METs, 2 wk) was measured by wrist-worn accelerometer and body fat percentage (Fat%) by bioimpedance. RESULTS: In men, CRF and Fat% were significantly associated with higher rMSSD (standardized ß = 0.31 and -0.16) and HRR (ß = 0.19 and -0.18), whereas higher MVPA was linked with higher HRR (ß = 0.13) when including CRF, MVPA, and Fat% in the initial regression. After adjustments for other lifestyle and cardiometabolic factors, CRF remained significantly associated with rMMSD (ß = 0.24) and HRR (ß = 0.14), as did MVPA with HRR (ß = 0.11). In women, CRF was associated with rMSSD (ß = 0.23) and HRR (ß = 0.15), and MVPA (ß = 0.17) and Fat% (ß = -0.07) with HRR, when CRF, MVPA, and Fat% were adjusted for each other. After further adjustments, CRF remained a significant determinant of rMSSD (ß = 0.20) and HRR (ß = 0.13), as did MVPA with HRR (ß = 0.15). The final models explained 23% and 21% of variation in rMSSD and HRR in men, and 10% and 12% in women, respectively. CONCLUSIONS: CRF was a more important determinant of cardiac autonomic function than MVPA and body fat. Furthermore, MVPA but not body fat was independently associated with cardiac autonomic function in both men and women.

Lifelong Physical Activity and Cardiovascular Autonomic Function in Midlife.

PURPOSE: Physical activity (PA) associates with cardiovascular autonomic function, but the relationship with lifelong PA is unclear. We hypothesized that lifelong PA would associate with cardiovascular autonomic function in midlife. METHODS: At the age of 46 yr, the subjects of the prospective Northern Finland Birth Cohort 1966 were invited to examinations where vagally mediated heart rate variability (root mean square of the successive differences in RRi [rMSSD]) and cross-spectral baroreflex sensitivity (BRS) were analyzed from 3-min recordings of ECG and blood pressure in seated and standing positions. Three lifelong PA trajectory groups (active, semiactive, and inactive) were formed according to their self-reported frequencies of participation in PA at the ages of 14, 31, and 46 yr. Finally, 1283 men and 1779 women without cardiorespiratory diseases and diabetes had complete data on lifelong PA, covariates, and rMSSD, and 662 men and 807 women for BRS. RESULTS: In both sexes and measurement conditions, the active (P < 0.01) and semiactive groups (P < 0.05) had greater rMSSD than the inactive group, and the highest BRS was observed in the active group (ANOVA P = 0.001-0.032). In men, these differences were not significant when adjusted for 46-yr lifestyle (smoking, alcohol consumption, sleep, and sitting time), body mass index, waist-to-hip ratio, blood pressure, lipid status, and glucose status. In women, lifelong PA remained a significant independent determinant of seated and standing rMSSD and standing BRS. CONCLUSION: Higher lifelong PA was associated with better cardiovascular autonomic function in midlife. In women, this effect was independent, but in men, it seemed to be mediated by the other lifestyle and cardiometabolic factors.

Association between Birth Characteristics and Cardiovascular Autonomic Function at Mid-Life.

BACKGROUND: Low birth weight is associated with an increased risk of cardiovascular diseases in adulthood. As abnormal cardiac autonomic function is a common feature in cardiovascular diseases, we tested the hypothesis that low birth weight may also be associated with poorer cardiac autonomic function in middle-aged subjects. METHODS: At the age of 46, the subjects of the Northern Finland Birth Cohort 1966 were invited to examinations including questionnaires about health status and life style and measurement of vagally-mediated heart rate variability (rMSSD) from R-R intervals (RRi) and spontaneous baroreflex sensitivity (BRS) in both seated and standing positions. Maternal parameters had been collected in 1965-1966 since the 16th gestational week and birth variables immediately after delivery. For rMSSD, 1,799 men and 2,279 women without cardiorespiratory diseases and diabetes were included and 902 men and 1,020 women for BRS. The analyses were adjusted for maternal (age, anthropometry, socioeconomics, parity, gestational smoking) and adult variables (life style, anthropometry, blood pressure, glycemic and lipid status) potentially confounding the relationship between birth weight and autonomic function. RESULTS: In men, birth weight correlated negatively with seated (r = -0.058, p = 0.014) and standing rMSSD (r = -0.090, p<0.001), as well as with standing BRS (r = -0.092, p = 0.006). These observations were verified using relevant birth weight categories (<2,500 g; 2,500-3,999 g; ≥4,000 g). In women, birth weight was positively correlated with seated BRS (r = 0.081, p = 0.010), but none of the other measures of cardiovascular autonomic function. These correlations remained significant after adjustment for potential confounders (p<0.05 for all). CONCLUSIONS: In men, higher birth weight was independently associated with poorer cardiac autonomic function at mid-life. Same association was not observed in women. Our findings suggest that higher, not lower, birth weight in males may contribute to less favourable cardiovascular autonomic regulation and potentially to an elevated cardiovascular risk in later life.