Heritability of somatotype components: a multivariate analysis

OBJECTIVE: To study the genetic and environmental determination of variation in Heath-Carter somatotype (ST) components (endomorphy, mesomorphy and ectomorphy). DESIGN: Multivariate path analysis on twin data. SUBJECTS: Eight hundred and three members of 424 adult Flemish twin pairs (18-34 years of age). RESULTS: The results indicate the significance of sex differences and the significance of the covariation between the three ST components. After age-regression, variation of the population in ST components and their covariation is explained by additive genetic sources of variance (A), shared (familial) environment (C) and unique environment (E). In men, additive genetic sources of variance explain 28.0% (CI 8.7-50.8%), 86.3% (71.6-90.2%) and 66.5% (37.4-85.1%) for endomorphy, mesomorphy and ectomorphy, respectively. For women, corresponding values are 32.3% (8.9-55.6%), 82.0% (67.7-87.7%) and 70.1% (48.9-81.8%). For all components in men and women, more than 70% of the total variation was explained by sources of variance shared between the three components, emphasising the importance of analysing the ST in a multivariate way. CONCLUSIONS: The findings suggest that the high heritabilities for mesomorphy and ectomorphy reported in earlier twin studies in adolescence are maintained in adulthood. For endomorphy, which represents a relative measure of subcutaneous adipose tissue, however, the results suggest heritability may be considerably lower than most values reported in earlier studies on adolescent twins. The heritability is also lower than values reported for, for example, body mass index (BMI), which next to the weight of organs and adipose tissue also includes muscle and bone tissue. Considering the differences in heritability between musculoskeletal robustness (mesomorphy) and subcutaneous adipose tissue (endomorphy) it may be questioned whether studying the genetics of BMI will eventually lead to a better understanding of the genetics of fatness, obesity and overweight.     

Sympathetic activity, assessed by power spectral analysis of heart rate variability, in white-coat, masked and sustained hypertension versus true normotension

OBJECTIVE: To assess, in a population-based approach, sympathetic nervous system activity by the use of power spectral analysis of heart rate variability, in normotension, white-coat hypertension, masked hypertension and sustained hypertension. METHODS: The electrocardiographic RR interval was registered in the supine and standing positions and the low-frequency and high-frequency components of its variability were quantified. Cut-off values of 140/90 mmHg for conventional blood pressure and 135/85 mmHg for daytime ambulatory blood pressure were used to define the four blood pressure groups. RESULTS: After exclusion of patients with diabetes, myocardial infarction or treated hypertension, 1485 subjects with complete data remained for the analysis in the supine position. Age averaged 39 +/- 14 years; 54% were women. Conventional and ambulatory blood pressure averaged, respectively, 122 +/- 16/79 +/- 11 mmHg and 124 +/- 12/77 +/- 8 mmHg. After adjusting for demographic, anthropometric and lifestyle characteristics, the low-frequency to high-frequency ratio (geometric mean) averaged 0.81 in normotension and was significantly higher in white-coat hypertension (1.11; P < 0.001), based on a higher low-frequency component and a lower high-frequency component (P < 0.01). This ratio was not significantly different between normotension, masked hypertension (0.97) and sustained hypertension (0.93). The adjusted standing-to-supine ratio of the high-frequency component (geometric mean) was significantly higher in sustained hypertension (0.50) than in normotension (0.39; P < 0.01), but not in white-coat (0.40) and masked hypertension (0.45). CONCLUSION: The findings at rest are compatible with increased sympathetic activity and decreased parasympathetic modulation in white-coat hypertension, with normal autonomic cardiac regulation in masked and sustained hypertension. In addition, sustained hypertension is characterized by a blunted decrease of the high-frequency component on standing.     

Change in imitation for object manipulation between 10 and 12 months of age

By the end of the first year, infants show dramatic increases in manual skill. In this study we tested one factor likely to contribute to this change: an increase in the capacity for observational learning, which may enable infants to learn new behaviors and practice ones that they already possess. Thus, we evaluated change in imitation between 10 and 12 months of age. Twelve 10‐month‐olds and twelve 12‐month‐old infants were shown different kinds of manual actions on a variety of objects; infants also manipulated objects during a free play control condition. Results indicated that older infants benefited more than younger ones in the Demonstration condition and that at both ages, infants performed the target action more quickly after observing a demonstration. We hypothesize that observational learning can help manual skill development by enabling infants to learn new actions and select and practice ones already in their skill set. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 52: 90–99, 2010     

Effects of immediate versus delayed antihypertensive therapy on outcome in the Systolic Hypertension in Europe Trial

BACKGROUND: To assess the impact of immediate versus delayed antihypertensive treatment on the outcome of older patients with isolated systolic hypertension, we extended the double-blind placebo-controlled Systolic Hypertension in Europe (Syst-Eur) trial by an open-label follow-up study lasting 4 years. METHODS: The Syst-Eur trial included 4695 randomized patients with minimum age of 60 years and an untreated blood pressure of 160-219 mmHg systolic and below 95 mmHg diastolic. The double-blind trial ended after a median follow-up of 2.0 years (range 1-97 months). Of 4409 patients still alive, 3517 received open-label treatment consisting of nitrendipine (10-40 mg daily) with the possible addition of enalapril (5-20 mg daily), hydrochlorothiazide (12.5-25 mg daily), or both add-on drugs. Non-participants (n = 892) were also followed up. RESULTS: Median follow-up increased to 6.1 years. Systolic pressure decreased to below 150 mmHg (target level) in 2628 participants (75.0%). During the 4-year open-label follow-up, stroke and cardiovascular complications occurred at similar frequencies in patients formerly randomized to placebo and those continuing active treatment. These rates were similar to those previously observed in the active-treatment group during the double-blind trial. Considering the total follow-up of 4695 randomized patients, immediate compared with delayed antihypertensive treatment reduced the occurrence of stroke and cardiovascular complications by 28% (P = 0.01) and 15% (P = 0.03), respectively, with a similar tendency for total mortality (13%, P = 0.09). In 492 diabetic patients, the corresponding estimates of long-term benefit (P < 0.02) were 60, 51 and 38%, respectively. CONCLUSIONS: Antihypertensive treatment can achieve blood pressure control in most older patients with isolated systolic hypertension. Immediate compared with delayed treatment prevented 17 strokes or 25 major cardiovascular events per 1000 patients followed up for 6 years. These findings underscore the necessity of early treatment of isolated systolic hypertension.     

Relationships of heart rate and heart rate variability with conventional and ambulatory blood pressure in the population

BACKGROUND: Most studies on relationships between blood pressure and autonomic nervous function, assessed by power spectral analysis of heart rate variability, have used conventional or clinic blood pressure measurements in selected subjects, which may have influenced the results. OBJECTIVE: We aimed to investigate, in a population-based approach, associations of heart rate and heart rate variability, assessed in basal resting conditions and in response to standing, with conventional blood pressure measured by an investigator, and with ambulatory blood pressure monitored outside the laboratory. METHODS: RR interval and respiration were registered in 614 men and women, ages 25-89 years. After exclusion of subjects with myocardial infarction or diabetes and elimination of unsatisfactory recordings, 549 subjects remained for analyses at supine rest and 515 of these to assess the orthostatic responses. Hypertension was present in 39% of the subjects. The low-frequency (LF) and high-frequency (HF) components of heart rate variability were quantified by use of autoregressive modelling and expressed in absolute and normalized units. RESULTS: At supine rest, indices of heart rate variability were not independently related to 24 h systolic blood pressure, whereas some indices showed weak associations with diastolic 24 h pressure; the relationships were in general stronger for conventional blood pressure. For example, partial correlation coefficients of the relationships of the LF: HF ratio with systolic pressure were 0.12 (P < or = 0.01) for conventional pressure and 0.02 (NS) for 24 h pressure; these coefficients amounted to 0.20 (P < or = 0.001) and 0.11 (P < or = 0.01) for the diastolic pressures. The decrease of HF power and the increase of the LF:HF ratio on standing were significantly blunted at higher blood pressure, both when measured conventionally and by ambulatory monitoring (P < or = 0.001 for the LF: HF ratio). CONCLUSIONS: Relationships between autonomic nervous function at rest, assessed by use of power spectral analysis of heart rate variability, and conventional blood pressure, can at least partly be ascribed to the influence of the measurement conditions, whereas the orthostatic autonomic responses appear to be influenced by blood pressure per se.     

Follow-up of renal function in treated and untreated older patients with isolated systolic hypertension. Systolic Hypertension in Europe (Syst-Eur) Trial Investigators

BACKGROUND: In the outcome trials that provided information on renal function in older hypertensive patients, diuretics and beta-blockers were mostly used as first-line drugs. The long-term renal effects of calcium-channel blockers remain unclear. OBJECTIVE: To compare the changes in renal function in 2,258 treated and 2,148 untreated patients with isolated systolic hypertension, of whom 455 had diabetes mellitus and 390 had proteinuria. METHODS: We performed a post-hoc analysis of the double-blind placebo-controlled Systolic Hypertension in Europe (Syst-Eur) Trial. Active treatment was initiated with nitrendipine (10-40 mg/day) with the possible addition of enalapril (5-20 mg/day), hydrochlorothiazide (12.5-25 mg/day), or both, titrated or combined to reduce the sitting systolic blood pressure by at least 20 mmHg, to less than 150 mmHg. The main outcome measures were serum creatinine concentration and creatinine clearance calculated by the formula of Cockroft and Gault. RESULTS: Serum creatinine concentration at the time when participants were randomly allocated to study groups was less than 176.8 micromol/l (2.0 mg/dl), averaging 88 micromol/l. At the time of the last serum creatinine measurement, the blood pressure difference (P< 0.001) between the two groups was 11.6/4.1 mmHg. In the intention-to-treat analysis (11,427 patient-years), serum creatinine and the calculated creatinine clearance were not influenced by active treatment. However, in the patients assigned randomly to receive active treatment, the incidence of mild renal dysfunction (serum creatinine at least 176.8 mmol/l) decreased by 64% (P= 0.04) and that of proteinuria by 33% (P= 0.03). Active treatment reduced the risk of proteinuria more in diabetic than in non-diabetic patients: by 71%, compared with 20% (P= 0.04). In non-proteinuric patients, active treatment did not influence serum creatinine, whereas in patients with proteinuria at entry to the study, serum creatinine decreased on active treatment (P< 0.001). Furthermore, in on-randomized treatment comparison stratified for risk at baseline, serum creatinine concentration did not change (P= 0.98) in patients continuing to receive monotherapy with nitrendipine, whereas it increased by 6.73 mmol/l (P < 0.001) in patients who received hydrochlorothiazide alone or in combination with other study medication (P < 0.001 for difference in trends). CONCLUSIONS: In older patients with isolated systolic hypertension, antihypertensive treatment starting with the dihydropyridine calcium-channel blocker, nitrendipine, did not decrease blood pressure at the expense of renal function and prevented the development of proteinuria, especially in diabetic patients.     

Prognostic significance of blood pressure measured in the office, at home and during ambulatory monitoring in older patients in general practice

The purpose of the study was to assess the prognostic significance of out-of-the-office blood pressure (BP) measurement in older patients in general practice, and to compare the results for BP measured in the office, at home and during 24-h ambulatory monitoring. All registerd patients who were 60 years or older were eligible for the study, except when bedridden, demented or admitted in a home for sick elderly people, or when they had suffered a myocardial infarction or stroke. After baseline measurements in 1990-1993, incidence of major cardiovascular events (cardiovascular death, myocardial infarction and stroke) was ascertained in 2002-2003 and related to the BPs by use of multivariate Cox regression analysis. Age of the 391 patients averaged 71+/-9 years; 40% were men. During median follow-up of 10.9 years, 86 patients (22%) suffered a cardiovascular event. The adjusted relative hazard rate, associated with a 1 s.d. increment in systolic BP was 1.13 for office BP (NS), and, respectively, 1.32, 1.33 and 1.42, for home, daytime and night time BP (P< or =0.01 for all). Results were similar for diastolic BP. The prognostic significance of all out-of-the-office BPs was independent of office BP. The prognostic value of home BP was equal to (systolic) or even better (diastolic) than that of daytime BP. Night time BP predicted cardiovascular events independent of all other BPs. Prognosis of white-coat hypertension was similar to that of true normotension, but better than in sustained hypertension. In conclusion, the prognostic value of home BP is better than that of office BP in older patients in primary care, and is at least equal to that of daytime ambulatory BP. The prognosis of patients with white-coat hypertension is similar to that of true normotensives.     

Exercise performance and training in cardiac patients with atrial fibrillation

PURPOSE: Exercise training in cardiac patients with chronic atrial fibrillation (AF) has received little attention in the literature. Therefore, this study compared exercise performance and the effect of an exercise training program over a period of 3 months in patients with and without AF. METHODS: Data in patients with AF (n = 19) were compared with a control group of patients in sinus rhythm (n = 44), drawn from a database of 2,116 patients. Patients performed a maximal exercise test on the bicycle until exhaustion before and after an ambulatory exercise training program where exercise training was offered 3 times a week for 3 months. RESULTS: Before training, peak oxygen uptake (VO2) was significantly lower in patients with AF compared with the control group (1271 +/- 368 versus 1496 +/- 414 mL/min, P < 0.05). Exercise training significantly increased peak VO2 in both groups (+31%, P < 0.001 in AF and +25%, P < 0.001 in the control group). The gain in peak VO2 did not significantly differ between both groups. A significant decrease in resting heart rate was achieved in both groups after exercise training. AF was also a significant and independent determinant of peak VO2 in the total database, but not of the change in peak VO2. CONCLUSIONS: Exercise training significantly improves exercise performance in cardiac patients with AF. AF affects exercise performance but does not impair the beneficial effects of training. Patients with chronic AF should therefore not be dissuaded from participating in exercise training after a cardiac event.