Background: A declining trend in mean cholesterol levels and smoking has been observed in high-income western countries during the last few decades, whereas obesity rates have increased. Simultaneously, mortality from coronary heart disease has decreased. The aim of the present study was to determine whether the trends in cardiovascular risk factors have continued in successive cohorts of middle-aged women over a period of 34 years. Methods: Six population-based, cross-sectional samples of women (n = 2294) mean age: 49.8 years (range: 45–54), living in Gothenburg, Sweden, were investigated between 1980 and 2014. Results: Body mass index (BMI) increased over time, with a mean BMI of 24.7 kg/m2 in 1980 to 25.7 kg/m2 in 2013–2014, corresponding to a weight gain of 4.5 kg, together with an increase in the proportion of obese individuals (BMI ≥ 30 kg/m2) from 10.4 to 16.6% (p = 0.0012). The proportion of smokers and women with hypertension decreased from 34.5 to 12.8% (p = 0.0006) and from 37.7 to 24.5% (p < 0.0001) respectively. Mean total serum cholesterol levels decreased from 6.23 (SD 1.09) mmol/L in 1980 to 5.43 (SD 0.98) mmol/L in 2013–2014 (p < 0.0001). Self-reported leisure time regular exercise increased from 7.8% in 1980 to 35.6% in 2013–2014 (p < 0.0001). For women born in 1963, the prevalence ratio of not having any of five major cardiovascular risk factors was 1.82 (95% confidence interval (CI) 1.38–2.41), compared with women born in 1925–1934. Conclusion: The trend towards increasing obesity, more leisure-time physical activity and less smoking remains, while the decrease in serum cholesterol appears to have abated.
Keywords: Epidemiology; Obesity; Physical activity; Population health
Since the 1970s, declining mortality trends in coronary heart disease have been observed inside and outside Europe, [[
In health promotion work, it is important for health-care providers and society to be aware of changes in risk factors over time. Few studies have provided information on secular trends in cardiovascular risk factors over an extended period [[
The aim of the present study was to determine whether the trends in predefined cardiovascular risk factors, obesity, hypertension, hypercholesterolemia, diabetes or smoking among middle-aged women have been maintained over time, by adding a sixth cohort of randomly selected middle-aged women, living in the same geographical area, and investigated using the same methodology as for the previous five cohorts.
The study population comprised 2294 women from six randomly selected cohorts of middle-aged women, all living in the city of Gothenburg, Sweden, who, between 1980 and 2014, participated in investigations (Table 1). Data on cardiovascular and coronary heart disease risk factors were collected using standardised questionnaires and physical examinations.
Participation rates in six cohorts of middle-aged women living in Gothenburg, Sweden
Birth year Year of examination Age at examination, years Number invited Number examined Participation rate (%) 1925–1934 1980 45–54 754 618 82 1931–1940 1985 45–54 246 207 84 1936–1945 1990 45–54 291 218 75 1941–1950 1995 45–54 354 241 68 1953 2003–2004 50–51 994 667 67 1963 2013–2014 50 645 343 53
Cohort 1 consists of a sample of women, born in 1925–1934 and aged 45–54 years when investigated between November 1979 and February 1981, from the Gothenburg BEDA study [[
Cohorts 2, 3 and 4 consist of randomly sampled women aged 45 to 54 years participating in the WHO MONICA project, GOT-MONICA, [[
Cohort 5 derives from "The study of men and women born in 1953" [[
Secular trends in risk factor patterns in these five cohorts have previously been presented [[
Data on smoking habits, leisure-time physical activity, mental stress, previous diseases and pharmacological treatments were obtained by questionnaires. Height was recorded to the nearest centimetre. Body weight was measured on a lever balance to the nearest 0.1 kg with the women barefoot and wearing light indoor clothing. Waist circumference was measured in cm at the level of the umbilicus. Body mass index (BMI, weight in kg/(height in m)
Blood pressure was measured, using a mercury manometer, in a seated position after at least 5 min' rest and before venpuncture. Hypertension was defined as systolic blood pressure of > 140 mmHg and/or diastolic blood pressure of > 90 mmHg and/or treatment with antihypertensive agents.
Blood samples were drawn from the antecubital vein. Analyses of total serum cholesterol and triglyceride measurements were determined according to standard laboratory procedures. In cohorts 1–5, all the women were investigated in the morning after an overnight fast. In Cohort 6, for practical reasons, almost one third of the women were investigated in the afternoon after at least 4 h of fasting.
The diagnosis of diabetes mellitus was self-reported in the questionnaire. The women were classified as never smokers, former smokers or current smokers. The category of current smokers includes women who had quit smoking less than 1 month before the investigation.
Leisure-time level was assessed using the Saltin-Grimby Physical Activity Level Scale (SGPALS) [[
Mental stress was defined as feeling tense, irritable or filled with anxiety or having sleeping difficulties because of conditions at work or at home. The mental stress questionnaire comprises six response categories: 1 = never experienced stress; 2 = one period of stress ever; 3 = some periods of stress during the past 5 years; 4 = several periods of stress during the past 5 years; 5 = permanent stress during the past year and 6 = permanent stress during the past 5 years. Permanent stress was defined by category 5 or 6 [[
The study complies with the Declaration of Helsinki.
The statistical analysis, data management and graphical presentation were conducted in SAS 9.3 (SAS Institute, Gary, North Caroline, USA). Each cohort was assigned a sequential number from 1 to 6, related to the order of the year of birth. The descriptive results are presented as a mean (standard deviation) for continuous data and as a frequency (percentage) for categorical data. One-way ANOVA was used to compare group means and the Cochran-Mantel-Haenszel test was used to examine differences in proportions, when a linear association between study groups was hypothesised. Equality of proportions was assessed with the χ
As shown in Table 1, the participation rates decreased, from over 80% in the first two cohorts, to 53% in the latest cohort. Table 2 shows anthropometric measurements, cardiovascular risk factors, physical activity levels and permanent stress in all six cohorts of women. From the first investigation in 1980 to the last in 2013–2014, the mean height and body weight increased by about two centimetres to 165.9 cm (P for trend < 0.0001) and 4.5 kg to 70.7 kg (P for trend < 0.0001) respectively. The mean waist circumference increased markedly; from 80.1 cm in 1985 to 88.4 cm in 2013–2014 (waist circumference was not measured in the first cohort). The proportion of obese women increased from 10.4 to 16.6% from 1980 to 2013. Throughout the same period, there was a trend towards a lower prevalence of hypertension.
Secular trends in cardiovascular risk factors in six cohorts of middle-aged women
Cohort 1 Born 1925–1934 Year of examination 1980 Cohort 2 Born 1931–1940 Year of examination 1985 Cohort 3 Born 1936–1945 Year of examination 1990 Cohort 4 Born 1941–1950 Year of examination 1995 Cohort 5 Born 1953 Year of examination 2003–2004 Cohort 6 Born 1963 Year of examination 2013–2014 Cohort 5 versus cohort 6 Mean change between the studied cohorts Variables Age, mean (SD) 49.5 (2.9) 49.8 (2.9) 49.1 (2.6) 49.7 (2.5) 50.2 (0.4) 50.0 (.0) Age, median (Q1; Q3) 49 (47; 52) 50 (47; 52) 49 (47; 51) 50 (48; 51) 50 (50; 50) 50 (50; 50) Height, cm 163.8 (5.8) 164.9 (6.2) 165.4 (6.1) 166.0 (6.4) 166.0 (6.8) 165.9 (6.6) < 0.0001 n.s. 0.40 (0.10–0.70) 0.020 Weight, kg 66.2 (10.8) 65.9 (11.3) 68.1 (12.7) 69.2 (11.9) 70.5 (13.0) 70.7 (14.0) < 0.0001 n.s. 1.06 (0.66–1.47) 0.0019 Waist circumference, cm – 80.1 (10.7) 77.9 (10.4) 80.7 (10.3) 83.1 (11.4) 88.4 (11.7) < 0.0001 <.0001 2.20 (−0.17; 4.57) 0.060 BMI, kg/m2 24.7 (3.9) 24.3 (4.0) 24.9 (4.5) 25.1 (4.2) 25.6 (4.5) 25.7 (4.9) < 0.0001 n.s 0.27 (0.09–0.44) 0.014 BMI four categories, % (n) 0.0012 n.s BMI < 20 4.7 (29) 11.1 (23) 6.9 (15) 7.9 (19) 5.0 (33) 7.3 (25) 1.01 (0.93–1.11) 0.78 20 ≤ BMI < 25 55.5 (343) 54.6 (113) 55.1 (120) 49.0 (118) 49.2 (328) 47.2 (162) 0.93 (0.89–0.98) 0.0021 25 ≤ BMI < 30 29.5 (182) 25.6 (53) 25.7 (56) 32.0 (77) 30.7 (205) 28.9 (99) 1.02 (0.97–1.07) 0.51 BMI ≥ 30 10.4 (64) 8.7 (18) 12.4 (27) 11.2 (27) 15.1 (101) 16.6 (57) 1.13 (1.05–1.21) 0.0005 Systolic BP, mmHg, mean (SD) 135.3 (20.7) 128.7 (18.5) 125.5 (17.0) 128.4 (17.9) 123.1 (19.0) 129.3 (16.5) < 0.0001 <.0001 −1.25 (−3.75; 1.24) 0.24 Diastolic BP, mmHg, mean (SD) 85.1 (11.1) 81.0 (9.4) 80.2 (9.3) 82.9 (9.9) 82.6 (10.8) 81.6 (9.8) < 0.0001 n.s −0.29 (−1.5; 0.92) 0.55 Blood pressure treatment, % (n) 9.71 (60) 6.28 (13) 10.55 (23) 7.88 (19) 9.60 (64) 7.62 (26) n.s. n.s. 0.98 (0.91–1.06) 0.66 Hypertension, % (n) 37.7 (233) 29.5 (61) 25.7 (56) 30.3 (73) 29.7 (198) 24.5 (84) < 0.0001 0.081 0.91 (0.87–0.95) < 0.0001 Serum cholesterol, mmol/L 6.23 (1.09) 6.23 (1.21) 5.82 (1.15) 5.60 (1.08) 5.44 (0.93) 5.43 (0.98) < 0.0001 n.s. −0.19 (−0.26; −0.11) 0.0025 Serum triglycerides, mmol/L 1.07 (0.54) 1.17 (0.68) 1.27 (0.51) 1.38 (0.75) 1.24 (1.14) 1.05 (0.67) < 0.0001 0.0007 0.01 (−0.09; 0.10) 0.87 Self-reported diabetes, % (n) 1.78 (11) 2.42 (5) 0.92 (2) 2.07 (5) 1.95 (13) 1.17 (4) n.s. n.s. 0.97 (0.82–1.15) 0.72 Smoking habits, % (n) 0.0006 0.0006 Never smoked 51.7 (319) 44.9 (92) 53.2 (116) 45.2 (109) 37.5 (250) 58.6 (201) 0.97 (0.93–1.01) 0.13 Former smokers 13.8 (85) 20.0 (41) 15.6 (34) 29.5 (71) 36.3 (242) 28.6 (98) 1.28 (1.21–1.35) < 0.0001 Current smokers, 1–14 g/day 22.2 (137) 13.7 (28) 11.9 (26) 8.7 (21) 16.4 (109) 7.6 (26) 0.86 (0.81–0.91) < 0.0001 Current smokers, > 14 g/day 12.3 (76) 21.5 (44) 19.3 (42) 16.6 (40) 9.8 (65) 5.2 (18) 0.88 (0.82–0.94) < 0.0001 Physical activity in leisure time, % (n) < 0.0001 0.0003 Sedentary 23.5 (145) 19.5 (40) 13.5 (29) 28.6 (50) 13.8 (92) 10.5 (36) 0.85 (0.80–0.90) < 0.0001 Light PA 68.7 (424) 73.2 (150) 75.8 (163) 56.0 (98) 62.3 (415) 53.9 (185) 0.88 (0.84–0.92) < 0.0001 Regular PA 7.8 (48) 7.3 (15) 10.7 (23) 15.4 (27) 23.9 (159) 35.6 (122) 1.49 (1.39–1.60) < 0.0001 Permanent stress, % (n) 16.4 (101) 16.1 (33) 19.5 (42) 17.0 (25) 22.8 (151) 22.2 (76) 0.0016 n.s. 1.09 (1.03–1.16) 0.0017 Born in Sweden, % (n) 86.57 (535) 81.33 (196) 76.61 (511) 75.22 (258) < 0.0001 n.s. 0.85 (0.80–0.91) < 0.0001
Continuous variables are presented as the mean (SD). Proportions are presented as percentages (number). BMI Body mass index; BP Blood pressure Waist data were missing in the first cohort and for another 10 women, a total of 628 women Body mass index data were missing for nine women Systolic blood pressure data were missing for 21 women Diastolic blood pressure data were missing for 29 women Triglyceride data were missing for 28 women A diabetes history was missing for two women A history of smoking was missing for four women A history of physical activity level during leisure time was missing for 73 women Data on self-perceived stress were missing for 106 women
Mean serum cholesterol decreased from 6.23 (SD 1.09) mmol/L in 1980 to 5.43 (SD 0.98) mmol/L in 2013–2014. The proportion of women with self-reported diabetes mellitus was low, ranging between 1.0 and 2.4%, without any significant change over time. The decrease in smoking has continued and, in the latest cohort, 13% of the women were current smokers, in contrast to 34.5% registered in the first cohort. High-intensity leisure-time physical activity has steadily increased over the decades. In the latest cohort, 35.6% of the women reported being physically active at an intensive level on a regular basis. Simultaneously, the proportion of women with a sedentary lifestyle declined from 23.5 to 10.5%. Self-reported permanent stress has increased over the years, but, in the latest cohort, women born in 1963, no further increase was found compared with women born in 1953.
When comparing only the latest two cohorts, a significant increase was observed in waist circumference, systolic blood pressure and physical activity during leisure time, while there was a significant decrease in s-triglycerides and the number of smokers (Table 2).
Table 3 shows the prevalence ratios (PRs) for having none and one to four or five of the predefined cardiovascular risk factors (body mass index ≥25, hypertension, serum cholesterol > 5 mmol/L, diabetes and smoking), with women born in 1925–1934 (Cohort 1) as a reference. For women born in 1963, the PR for not having any of the predefined risk factors was 1.82 (95% confidence interval (CI) 1.38–2.41), while the PR for having four or five risk factors was 0.75 (95% CI 0.64–0.88). The percentage of participants with 0, 1, 2, 3 or 4–5 of the predefined risk factors is presented in Fig. 1.
Prevalence ratios (PRs) for the number of predefined cardiovascular risk factors in six cohorts of middle-aged women
O risk factor 1 risk factor 2 risk factors 3 risk factors 4 risk factors Year of birth n PR 95% CI n PR 95% CI n PR 95% CI n PR 95% CI n PR 95% CI 1925–1934 32 1.00 164 1.00 229 1.00 166 1.00 27 1.00 1931–1940 15 1.11 0.91–1.35 60 1.03 0.94–1.13 85 1.04 0.96–1.13 38 0.89 0.82–0.97 9 1.00 0.82–1.21 1936–1945 22 1.26 1.01–1.58 72 1.09 0.99–1.20 79 0.99 0.91–1.08 38 0.88 0.81–0.95 7 0.93 0.78–1.11 1941–1950 34 1.52 1.18–1.96 74 1.06 0.96–1.17 72 0.92 0.84–1.00 55 0.94 0.86–1.03 6 0.87 0.74–1.03 1953 96 2.03 1.49–2.75 208 1.13 0.99–1.29 206 0.87 0.77–0.98 130 0.81 0.72–0.92 27 0.96 0.73–1.26 1963 55 1.82 1.38–2.41 131 1.23 1.09–1.37 101 0.89 0.81–0.98 51 0.79 0.72–0.87 5 0.75 0.64–0.88
Cardiovascular risk factors: body mass index ≥25, hypertension, serum cholesterol > 5 mmol/L, diabetes and smoking Women born in 1925–1934 served as the reference group. In all, there were 36 women with missing data. CI Confidence interval; PR Prevalence ratio
Graph: Fig. 1 Percentage of participants with 0, 1, 2, 3 or 4–5 of 5 predefined cardiovascular risk factors in six cohorts of middle-aged women examined in: 1980, 1985, 1990, 1995, 2003–2004 and 2013–2014
The women who reported a regular/athletic physical activity level did not increase their mean BMI over time and nor did sedentary women. However, in those reporting moderate leisure-time physical activity levels, BMI increased significantly in successive cohorts (Fig. 2).
Graph: Fig. 2 Mean body mass index (MBI) (x-axis) in six cohorts of middle-aged women with different levels of physical activity during leisure time (Y-axis)
In the latest studied cohort, the trend towards increasing obesity, more leisure-time physical activity and less smoking remains, while the decrease in total serum cholesterol appears to have abated, with essentially identical mean levels in the two last cohorts. Since 1980, the prevalence ratio for not having any of the five predefined cardiovascular risk factors was more than 80% higher, while the prevalence ratio for having four or five of these risk factors decreased by 25%. These results are consistent with previously reported secular trends for men in the same region [[
The pattern of reduced smoking and increased BMI is also similar to the results of the MONICA study from northern Sweden [[
In all six cohorts, the prevalence of diabetes mellitus was low, reflecting the general, comparatively low prevalence in the Swedish population [[
Even a minor increase in blood pressure levels in a large population may lead to marked increases in the burden of cardiovascular disease in the community [[
The trend towards an increasing level of leisure-time physical activity has also been observed in other countries such as Finland, Scotland, the USA, Canada, Taiwan and Australia [[
In spite of the positive trend towards fewer smokers, they still account for 13% of the population. People who smoke often have other cardiovascular risk factors and a study of Norwegian adults showed that smokers were more likely to have low leisure-time physical activity levels compared with non-smokers [[
Mental stress may act as a trigger for major cardiac events and influence the prognosis of cardiovascular disease and the progress of stress cardiomyopathy [[
The trend towards declining serum cholesterol levels over time did not continue between 2003 and 2013–2014. The same trend was observed among Swedish men from the same geographical area [[
The main strength of this study is the well-defined population samples of women living in the same geographical area and examined at the same age with the same methods over three decades.
However, there are also some potential limitations to be considered. First, the cohort sizes were relatively small. Second, there is a risk of selection bias with decreasing participation rates, as participating women may differ from non-participating women. Participants in population studies tend to have a higher socioeconomic status and to be healthier than non-participants [[
The trend towards increasing obesity, more leisure-time physical activity and less smoking remains, while the decrease in serum cholesterol appears to have abated. Compared with 1980, the prevalence ratio for not having any of the five major cardiovascular risk factors was almost twice as high in 2013–2014. In spite of this, with one in seven women still smoking, one in six obese and a markedly increasing waist circumference, continuing efforts are necessary to improve health literacy and lifestyle changes, particularly in relation to preventing obesity.
The authors disclose the receipt of the following financial support for the research, authorship and/or publication of this paper. The study was financed by grants from Anna Ahrenberg's Foundation and from the Swedish state under the agreement between the Swedish government and the county councils: the ALF agreement (ALFGBG-721351), AFA insurance, the Swedish Heart and Lung Foundation and the Swedish Research Council. Open access funding provided by University of Gothenburg.
The authors are very grateful to all the participating women and to the staff who contributed to the studies over the years.
AR, SJ, and POH contributed to the conception or design of the examinations. TZS made the statistical analysis. All the authors (CUP, ACC, AR, ZM, TZS, MF, MD, SJ and POH) contributed to the acquisition, analysis or interpretation of the data. CUP drafted the manuscript. All the authors revised the manuscript critically and agreed to be accountable for all aspects of the work, thereby ensuring integrity and accuracy. All the authors read and approved the final manuscript.
The datasets analysed during the current study are not publicly available, due to the protection of personal data, but they are available from one of the authors (POH) in response to a reasonable request.
The Ethical Committee of Gothenburg approved the study protocol (2013/649) on 25 September 2013. Oral and written informed consent was given by all participants prior to the study.
N.A.
The authors declare no potential conflicts of interest.
• PR
- Prevalence ratio
• SD
- Standard deviation
• BMI
- Body mass index
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