To Örebro University

Purpose: Arterial stiffness describes the rigidity of the arterial walls and is associated withrisk factors for cardiovascular disease (CVD). Arterial stiffness predicts future events andmortality, and the predictive value is stronger in younger versus older subjects. The aims ofthe present study were, firstly, to present data on physical activity (PA) and time spentsedentary, in the population of Swedish, young adults. Secondly, to explore the associationbetween PA and arterial stiffness.

Material and Methods: Self-reported healthy, non-smoking, Swedish, young adults, 18–25years old, participated in the cross-sectional Lifestyle, Biomarkers and Atherosclerosis(LBA) study. The daily PA was objectively measured with an accelerometer for 1 week.Of the 834 participants, 658 individuals had valid registrations. The arterial stiffness measures, pulse wave velocity (PWV) and augmentation index (AIx) were measured withapplanation tonometry.

Results: Women were on overall more physically active than men, they spent 214 min/dayin light PA (LPA) compared to men who spent 202 min/day. Women took significantly moresteps per day than men, 7796 vs 7336 steps/day, and spent less time sedentary, 523 min/day,compared to men who spent 547 min/day sedentary. In total, 76% of the individuals spent onaverage at least 30 minutes per day in the recommended moderate and vigorous PA (MVPA).Lower arterial stiffness was associated with more MVPA and total PA in the total population.

Conclusion: We conclude that in this age group of young, self-reported healthy adults18–25 years, it is important to highlight the health-enhancing possibilities of time spent inphysical activity on the vascular function, measured as PWV and AIx. It is of high relevancein a public health perspective to expand preventive efforts beyond the high-risk groups andencourage young adults to be physically active.

Background: In the cross-sectional Lifestyle, Biomarkers, and Atherosclerosis study (LBA study) we have previously reported a high prevalence (15%) of homeostasis model assessment of insulin resistance (HOMA-IR) in Swedish, young adults. The aim of the present study was to report the dietary habits of subjects 18.0-25.9years, and to associate dietary habits to body composition measures; body mass index (BMI), body fat (%), waist circumference and to HOMA-IR, a risk marker for diabetes.

Method: The subjects (577 women and 257 men) filled in a validated computerized food frequency questionnaire. The questionnaire was based on recommendations from the Swedish national food administration. To associate the dietary habits to BMI, body fat (%), waist circumference and to HOMA-IR the subjects were divided in two groups. Subjects "eating as recommended" and subjects "eating less/more than recommended".

Results: Recommended intake of fish and seafood (P <0.05), fruit and vegetables (P <0.001), and sweets (P<0.05) were associated to lower HOMA-IR values compared to subjects not eating as recommended. When split by sex no difference in HOMA-IR was detected with recommended intake of fish and seafood, but women eating fish and seafood as recommended had less body fat (%) (P <0.05) compared to women not eating fish and seafood as recommended. Recommended intake of fruit and vegetables was associated to lower HOMA-IR in women (P <0.01), and in women and men to less body fat (%) (P <0.05) compared to subjects not eating the recommended 500g of fruit and vegetables per day. Both women and men with higher consumption of sweets than recommended had higher HOMA-IR (P <0.05), but no difference in the body composition measures BMI, body fat (%) or waist circumference compared to subjects eating sweets as recommended.

Conclusion: The results highlight the importance of reducing a high intake of sweets and to increase the intake of fish, fruit and vegetables, in young adults, to reduce the risk of future diabetes.

BACKGROUND: Cardiorespiratory fitness (CRF) and sleep habits are lifestyle factors with potential to prevent cardiovascular disease (CVD). CVD is the leading cause of death worldwide. It is therefore important to establish a healthy lifestyle at a young age. In the Lifestyle, Biomarkers and Atherosclerosis (LBA) study we have examined 834 healthy non-smoking adults, aged 18-25 years. The general purpose of the LBA study was to study the effect of lifestyle on traditional biomarkers known to influence CVD risk. The aims of the present study were to evaluate sleep habits of young adult women and men participating in the LBA study, and to compare the importance of sleep and other lifestyle habits on clinically relevant biomarkers for CVD. An additional aim was to find easy and reliable non-invasive biomarkers to detect young adults with increased risk of developing CVD later in life.

METHODS: The participants had previously been examined for lifestyle factors, biomarkers and CVD risk score. They filled in a validated computerized questionnaire about their general physical and mental health. The questionnaire included questions on sleep duration and experienced quality of sleep.

RESULTS: In total 27% of the young adult participants reported difficulties falling asleep or experienced troubled sleep with frequent awakenings per night. The experienced troubled sleep was not related to a higher CVD risk score, but sleep quality and duration were correlated. Shorter sleep duration was significantly associated to higher body mass index (BMI), body fat (%), homeostasis model assessment of insulin resistance (HOMA-IR) and CVD risk. The modifiable lifestyle factor with the highest odds ratio (OR) for CVD risk was CRF. Sleep duration was the second most influential lifestyle factor, more important than moderate- and vigorous physical activity (MVPA) and food habits. Correlations between CRF and heart rate (HR), (P < 0.01) and HOMA-IR and BMI (P < 0.01) were observed, indicating that BMI and resting HR in combination with questions about sleep patterns are easy and reliable non-invasive biomarkers to detect young adults who need counselling on a healthy lifestyle.

CONCLUSION: Decreased sleep duration in combination with decreased CRF, in young adults, is a serious health issue.

Atherosclerosis is a complex, chronic vessel wall disease that often leads to severe and acute cardiovascular diseases (CVD), such as myocardial infarction and stroke. CVD are the most common cause of death, both globally and in Sweden. Since most of the risk factors for atherosclerosis are preventable, it is of great importance to highlight the benefits of a healthy lifestyle to young adults who are about to create their own habits.

A general concern about physical inactivity, low cardiorespiratory fitness (CRF), and high body mass are supported by reports of an increased incidence and prevalence of obesity worldwide. In addition to this, the proportion of Swedish adults with low CRF almost doubled the last 20 years and the decline in CRF is more pronounced in the youngest age group.

The scientific work presented in this thesis was carried out to investigate the impact of different lifestyle related factors on vascular status, especially arterial stiffness, in young Swedish adults. In total 840 young adults in the age range 18-25 years were recruited to the cross-sectional Lifestyle, Biomarkers, and Atherosclerosis (LBA) study, to examine vascular status, biomarkers, and lifestyle related factors.

In the LBA study population of young adults in Sweden, 12% were classified as being at risk of future CVD. A high CVD risk was associated with low CRF and less physical activity. In the total study population 24% had unhealthy food habits, and 24% did not spend the recommended 30 minutes per day at moderate or vigorous intensities of physical activity. Low CRF, less physical activity, and overweight and obesity, were associated with stiffer arteries.

The results raises concerns about future CVD risk and highlights the health enhancing possibilities of high CRF and physical activity on vascular status in young Swedish adults.

BACKGROUND: Obesity has nearly tripled worldwide during the last four decades, especially in young adults, and is of growing concern since it is a risk factor for cardiovascular diseases (CVD). We explored how different body composition measurements are associated with intima media thickness (cIMT) and local stiffness in the common carotid artery, in a subsample of healthy, young women and men, from the Swedish Lifestyle, Biomarkers, and Atherosclerosis (LBA) Study.

METHODS: From the LBA study, a subsample of 220 randomly selected, self-reported healthy individuals, 18-25 years old, were collected for the automatized local stiffness measurements; arterial distensibility, Young's elastic modulus, and β stiffness index. Blood pressure and mean arterial pressure (MAP) was measured using automatic blood pressure equipment. Body mass index (BMI) was calculated, waist circumference was measured, and percentage of body fat assessed using an impedance body composition analyzer. The carotid artery was scanned by ultrasound and analyzed using B-mode edge wall tracking. cIMT was measured and local stiffness measurements were calculated with carotid blood pressure, measured with applanation tonometry.

RESULTS: No association was found between cIMT and body composition. Local carotid stiffness was associated with body composition, and women had less stiff arteries than men (p < 0.001). Of the local stiffness measurements, arterial distensibility had the strongest associations with body composition measurements in both women and men (p < 0.05). Multiple regression analyses showed that BMI in women and BMI and percentage of body fat in men had the highest impact on arterial distensibility (p < 0.01 in both women and men).

CONCLUSIONS: Arterial distensibility was the local stiffness measurement with the strongest associations to different body composition measurements, in both women and men. In this age group, body composition measurements seem to be stronger predictors of common carotid arterial stiffness than MAP, and is a convenient way of detecting young adults who need cardiovascular risk follow-up and lifestyle counseling.

INTRODUCTION: Platelet aggregation and secretion can be induced by a large number of endogenous activators, such as collagen, adenosine diphosphate (ADP) and epinephrine. Conversely, the blood vessel endothelium constitutively release platelet inhibitors including nitric oxide (NO) and prostacyclin. NO and prostacyclin are also well-known vasodilators and contribute to alterations in local blood flow and systemic blood pressure.

MATERIALS AND METHODS: In this study we investigated individual variations in platelet reactivity and arterial functions including blood pressure and flow-mediated vasodilation (FMD) in 43 young, healthy individuals participating in the Lifestyle, Biomarkers and Atherosclerosis (LBA) study. Platelet aggregation and dense granule secretion were measured simultaneously by light transmission and luminescence. FMD was measured with ultrasound.

RESULTS: The platelet function assay showed inter-individual differences in platelet reactivity. Specifically, a sub-group of individuals had platelets with an increased response to low concentrations of ADP and epinephrine, but not collagen. When the NO-donor S-nitroso-N-acetyl-DL-penicillamine (SNAP) was combined with high doses of these platelet activators, the results indicated for sub-groups of NO-sensitive and NO-insensitive platelets. The individuals with NO-sensitive platelets in response to SNAP in combination with collagen had a higher capacity of FMD of the arteria brachialis.

CONCLUSIONS: Platelet reactivity towards ADP, epinephrine and NO differs between young, healthy individuals. Some individuals have a more effective response towards NO, both in the aspect of platelet inhibition ex vivo, as well as vasodilation in vivo.

Background: The progression of cardiovascular disease (CVD) and atherosclerosis is slow and develops over decades. In the cross-sectional Swedish Lifestyle, Biomarker, and Atherosclerosis study, 834 young, self-reported healthy adults aged 18.0-25.9 years have been studied to identify early risk factors for atherosclerosis.

Purpose: The aims of this study were to 1) assess selected cardiometabolic biomarkers, carotid intima-media thickness (cIMT) as a marker of subclinical atherosclerosis, and lifestyle-related indicators (food habits, handgrip strength, and oxygen uptake, VO(2)max);2) analyze the associations between cIMT and lifestyle factors; and 3) identify subjects at risk of CVD using a risk score and to compare the characteristics of subjects with and without risk of CVD.

Method: Blood samples were taken in a fasting state, and food habits were reported through a questionnaire. cIMT was measured by ultrasound, and VO2 max was measured by ergometer bike test. The risk score was calculated according to Wildman.

Result: cIMT (mean +/- standard deviation) was 0.50 +/- 0.06 mm, and VO2 max values were 37.8 +/- 8.5 and 42.9 +/- 9.9 mL/kg/min, in women and men, respectively. No correlation was found between aerobic fitness expressed as VO2 max (mL/kg/min) and cIMT. Using Wildman's definition, 12% of the subjects were classified as being at risk of CVD, and 15% had homeostasis model assessment of insulin resistance. A total of 35% of women and 25% of men had lower high-density lipoprotein cholesterol than recommended. Food habits did not differ between those at risk and those not at risk. However, aerobic fitness measured as VO2 max (mL/kg/min) differed; 47% of the subjects at risk had low aerobic fitness compared to 23% of the nonrisk subjects (P<0.001).

Conclusion: High aerobic fitness is associated with low CVD risk in Swedish young adults. The high prevalence of young adults observed with unfavorable levels of high-density lipoprotein cholesterol and homeostasis model assessment of insulin resistance raises concerns about future CVD risk.

Background: Early changes in the large muscular arteries are already associated with risk factors as hypertension and obesity in adolescence and young adulthood. The present study examines the association between arterial stiffness measurements, pulse wave velocity and augmentation index and lifestyle-related factors, body composition and cardiorespiratory fitness, in young, healthy, Swedish adults.

Design: This study used a population-based cross-sectional sample.

Methods: The 834 participants in the study were self-reported healthy, non-smoking, age 18-25 years. Augmentation index and pulse wave velocity were measured with applanation tonometry. Cardiorespiratory fitness was measured by ergometer bike test to estimate maximal oxygen uptake. Body mass index (kg/m(2)) was calculated and categorised according to classification by the World Health Organisation.

Results: Young Swedish adults with obesity and low cardiorespiratory fitness have significantly higher pulse wave velocity and augmentation index than non-obese young adults with medium or high cardiorespiratory fitness. The observed U-shaped association between pulse wave velocity and body mass index categories in women indicates that it might be more beneficial to be normal weight than underweight when assessing the arterial stiffness with pulse wave velocity. The highest mean pulse wave velocity was found in overweight/obese individuals with low cardiorespiratory fitness. The lowest mean pulse wave velocity was found in normal weight individuals with high cardiorespiratory fitness. Cardiorespiratory fitness had a stronger effect than body mass index on arterial stiffness in multiple regression analyses.

Conclusions: The inverse association between cardiorespiratory fitness and arterial stiffness is observed already in young adults. The study result highlights the importance of high cardiorespiratory fitness, but also that underweight individuals may be a possible risk group that needs to be further studied.