Abstract
Population-based lipid screening studies were initiated in the city of Leipzig, Germany, and included more than 30,000 subjects. The objectives of the Lipid Study Leipzig (LSL) were to evaluate the cardiovascular risk factor profile and its dependence on age, nutrition and social factors. In addition, the study results were compared with those of other population-based studies, and the development of cardiovascular risk factors over a 10-year period was evaluated. LSL data were obtained from subjects recruited at community centres, work sites, schools and the University of Leipzig, Germany. Capillary blood cholesterol and high-density lipoprotein-cholesterol levels were measured using the Reflotron dry-chemistry system (Roche Diagnostics, Germany). Study data also included blood pressure, body mass index, waist-to-hip ratio, and the evaluation of dietary and lifestyle factors. The results of LSL show an age-dependent increase in cardiovascular risk, which may have been partly preventable. Furthermore, LSL showed an improvement in cardiovascular risk, with respect to plasma cholesterol, over the past 10 years in men and women older than 30 and 50 years, respectively. The known age dependence of total cholesterol and non-high-density lipoprotein-cholesterol is less pronounced for those following a healthy lifestyle and for vegetarians. This suggests that the age-dependent rise of these parameters is partly preventable.
Keywords: Cardiovascular risk, Cholesterol, Dietary factors, HDL-cholesterol, Lifestyle factors
A Population-based lipid screening study – Lipid Study Leipzig (LSL) – was initiated in Leipzig, Germany, with the aim of identifying individuals who previously had undetected cardiovascular risk factors (1–6). The majority of subjects from the general population exhibited at least one risk factor for atherosclerosis, making these people more prone to developing cardiovascular diseases (7). Therefore, in LSL both the measurement of cardiovascular risk factors – such as lipid parameters, anthropometric parameters and blood pressure –and the evaluation of lifestyle and dietary parameters were included. Because there is overwhelming evidence that the occurrence of cardiovascular diseases can be reduced by making lifestyle modifications (8), individual consultations were designed to make recommendations regarding dietary habits, physical activity and other lifestyle factors such as smoking. Furthermore, the lipid and cardiovascular risk factor profile of participants in Leipzig was compared with that of other population-based studies for dependence on age and nutrition, and the development of risk factors in the past 10 years.
METHODS
LSL, a cross-sectional study, was initiated in Leipzig to evaluate the lipid and cardiovascular risk factor profile. The study program included capillary blood cholesterol measurements and the determination of high-density lipoprotein (HDL)-cholesterol levels using the Reflotron dry-chemistry system (Roche Diagnostics, Germany). Furthermore, the study program included measurements of weight and height (body mass index [BMI]), waist and hip circumference (waist-to-hip ratio), and blood pressure. The participants were questioned individually, and family histories regarding cardiovascular diseases, risk factors and metabolic disorders were recorded. Furthermore, lifestyle and dietary factors (smoking behaviour, physical activity and dietary habits) were evaluated. The assessments included an interview and a health habits and food frequency questionnaire (6). Risk evaluation was assessed from the individual consultations.
LSL recruited participants at community centres, work sites, schools in Leipzig and various faculties at the University of Leipzig, Germany, and included more than 30,000 subjects.
To study the possible influence of nutrition and lifestyle of vegetarians on lipid parameters, subjects from the general population were compared with vegetarians (vegans, lacto-vegetarians and lacto-ovo vegetarians). Recruitment of vegetarians was carried out mainly during meetings of the German Vegetarian Federation (Deutscher Vegetarierbund). Earlier studies were conducted to compare cohorts of Leipzig subjects with subjects from the cities of Nuremberg, Germany, and St Petersburg, Russia. The following studies were included in LSL:
Leipzig study – Nuremberg 1990/1991 (Leipzig: n=15,291; Nuremberg: n=8387);
Leipzig study 1992 (n=8546);
Leipzig study – St Petersburg 1995 to 1997 (Leipzig: n=3189; St Petersburg: n=1646);
Leipzig study 2001 to 2004 (n=2010); and
Vegetarian study (n=484).
Statistical analyses were performed using SPSS version 11.5.1 (SPSS Inc, USA). Statistical significance was assessed by non-parametric analysis (Mann-Whitney U test). The χ2 test was used to test statistical significance in the prevalence values.
RESULTS
Total cholesterol and non-HDL-cholesterol levels for both men and women in the general population showed the expected age-dependent increase (Table 1). No significant age dependence was seen regarding HDL-cholesterol.
TABLE 1.
Total cholesterol, non-high-density lipoprotein-cholesterol (non-HDL-C) and HDL-C (mean ± SD) in different age groups – Lipid Study Leipzig 2001–2004
| Age (years)
|
||||
|---|---|---|---|---|
| Level | 18–30 | 31–50 | 51–70 | > 70 |
| Men | ||||
| Cholesterol (mmol/L) | 4.43±0.88 | 5.43±1.02* | 5.58±0.99* | 5.48±0.91* |
| Non-HDL-C (mmol/L) | 3.08±0.93 | 3.99±1.10* | 4.14±1.02* | 4.11±0.98* |
| HDL-C (mmol/L) | 1.35±0.33 | 1.44±0.49 | 1.45±0.45 | 1.37±0.36 |
| Women | ||||
| Cholesterol (mmol/L) | 4.81±0.89 | 5.36±0.95* | 6.02±1.08* | 6.04±0.92* |
| Non-HDL-C (mmol/L) | 3.05±0.86 | 3.57±1.00* | 4.27±1.12* | 4.29±0.95* |
| HDL-C (mmol/L) | 1.76±0.37 | 1.80±0.44 | 1.75±0.41 | 1.75±0.41 |
P<0.001 versus age group 18 to 30 years
The prevalence of overweight/obesity (BMI 25.0 kg/m2 or greater) was higher than 50% in men older than 30 years and in women older than 50 years (Figure 1).
Figure 1.
Prevalence of overweight/obesity (body mass index [BMI] 25.0 kg/m2 or greater) in different age groups of the general population
The prevalence of a combination of four lipid and anthropometric risk parameters – total cholesterol greater than 5.2 mmol/L; total cholesterol to HDL-cholesterol ratio of at least 5.0 for men or 4.5 for women; BMI of 25.0 kg/m2 or greater; and waist-to-hip ratio of at least 0.9 for men or 0.8 for women – was dependent on age and showed a similar sex difference (Figure 2).
Figure 2.
Prevalence of a combination of four lipid and anthropometric risk parameters in different age groups of the general population: total cholesterol greater than 5.2 mmol/L; total cholesterol to high-density lipoprotein-cholesterol ratio of at least 5.0 for men or 4.5 for women; body mass index of 25.0 kg/m2 or greater; and waist-to-hip ratio of at least 0.9 for men or 0.8 for women
Vegetarians showed lower total cholesterol and non-HDL-cholesterol levels in comparison with the general population (Figure 3). Furthermore, the age-dependent increase of these parameters was less pronounced under the conditions of vegetarian nutrition and lifestyle.
Figure 3.
Total cholesterol levels in the general population and vegetarians by age group (males, mean ± SD). For the general population versus vegetarians: **P<0.01; ***P<0.001
To clarify possible changes in the cardiovascular risk factor profile of subjects in different age groups, within a 10-year period, the Leipzig studies of 1992 and of 2001 to 2004 were compared. However, in subjects younger than 50 years of age, no difference in BMI was observed. The prevalence of overweight/obesity in both men and women in the 51 to 70 years age group was significantly higher in 2001 to 2004 compared with 1992 (63.2% versus 56.2% in men, 54.9% versus 47.3% in women, P<0.05). LSL showed an improvement in the cardiovascular risk, with respect to plasma cholesterol, in men and women older than 30 and 50 years, respectively (Figures 4 and 5).
Figure 4.
Prevalence of cholesterol class >6.5 mmol/L in male subjects of different ages during a 10-year period. *P<0.05; ** P<0.01
Figure 5.
Prevalence of cholesterol class >6.5 mmol/L in female subjects of different ages during a 10-year period. **P<0.01
DISCUSSION
Population-based lipid screening projects were initiated in Leipzig and included more than 30,000 subjects. The objectives of LSL were to evaluate the cardiovascular risk factor profile and its dependence on age, nutrition and social factors (1–6). To clarify possible changes in the prevalence of cardiovascular risk factors within a 10-year period, the Leipzig studies of 1992 and of 2001 to 2004 were compared. Over the 10-year period, the prevalence of overweight/obesity increased in subjects older than 50 years, while cardiovascular risk, with respect to plasma cholesterol, decreased in men and women older than 30 and 50 years, respectively. Mean cholesterol levels and the prevalence of hypercholesterolemia (cholesterol levels greater than 6.5 mmol/L) were reduced over the 10-year study in both men and women. This improvement was seen independent of a percentage change of subjects who were on lipid-regulating therapy. Small reductions in the most important risk factors for atherosclerosis, such as hypercholesterolemia, smoking habits and hypertension, throughout the whole population may have led to substantial reductions in cardiovascular disease events (9–11). Therefore, the decreased prevalence of elevated plasma cholesterol levels may have been related to an improvement in the cardiovascular risk factor profile on a population basis.
The improvement in cardiovascular risk, regarding plasma cholesterol levels, may reflect the influence of changed dietary and lifestyle factors. The present results are in agreement with the estimation of the contribution of changes in risk factors to trends in coronary-event rates across the World Health Organization Multinational MONItoring of trends and determinants in CArdiovascular disease (WHO MONICA) Project populations (12,13). Earlier results from the Seven Countries Study (14) showed similar decreases in mean cholesterol levels in several populations.
CONCLUSIONS
The mean cholesterol and non-HDL-cholesterol concentrations, and the total cholesterol to HDL-cholesterol ratio showed the expected age dependence. Age-dependent changes of lipid metabolism may have arisen as a result of both mechanisms of biological aging and factors influencing age-dependent changes (6). To study possible influences of the nutrition and lifestyle of vegetarians on age dependence of lipid parameters, subjects in the general population were compared with vegetarians. Vegetarians showed lower total cholesterol and non-HDL-cholesterol levels in comparison with the general population. Furthermore, the age-dependent increase of these parameters was less pronounced in vegetarians. The results of the present study reveal the role of nutritional and lifestyle factors that determine the lipid profile on a population basis, and suggest that the known age-dependent rise of the level of atherogenic plasma lipoproteins is partly preventable.
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