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- Lilja, Mikael
(författare)
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Trends in obesity and type 2 diabetes : ethnic aspects and links to adipokines
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Objective The prevalence of obesity and related diseases such as type 2 diabetes mellitus (T2DM) is increasing worldwide, and the Asian Indian population seems to be particularly susceptible to developing T2DM, even at a low body mass index (BMI). In Sweden, the age-adjusted prevalence of diabetes has not increased despite increasing self-reported obesity. However, modern data on the prevalence of obesity and T2DM in Scandinavia are absent.The biochemical links between obesity and subsequent T2DM are unknown, but the adipocyte-derived hormones leptin and adiponectin (adipokines) have been suggested as potential links because they both are related to insulin and glucose physiology. Some studies have found leptin to be an independent predictor of T2DM in men but not in women, although these results are inconsistent. In contrast, adiponectin has more consistently been linked to development of T2DM in both men and women. Furthermore, the leptin–adiponectin ratio may predict incident T2DM better than either of the two hormones separately.The aims of this thesis were to describe time trends in obesity and T2DM in northern Sweden, to evaluate leptin and adiponectin as predictors of deterioration in glucose metabolism including T2DM, and to evaluate leptin as a risk marker regarding ethnic differences, circ-annual variation, and intra-individual stability. Materials and methods Three large population surveys were used, the Northern Sweden MONICA (MONitoring of Trends and Determinants in CArdiovascular Disease) study, the Västerbotten Intervention Programme (VIP), and the Mauritius Non-Communicable Disease Study. Within the MONICA study, six cross-sectional surveys were performed in Sweden’s two northernmost counties, Norrbotten and Västerbotten, between 1986 and 2009. A total of 1000 men and 1000 women ages 25–64 years, also including from 1994 250 men and 250 women ages 65–74 years, were independently chosen for each survey. The overall participation rate was 75%. In 1999, a reinvestigation was performed in 74% of all participants from the three first surveys. Data from the MONICA surveys were used in papers I and IV and data from the reinvestigation survey in paper II. VIP is an ongoing population intervention program that started in the mid-eighties targeting cardiovascular risk factors and has covered the whole county of Västerbotten since 1991. Inhabitants are invited the years they turn 40, 50, and 60 years old, and the annual participation rate has varied between 48% and 67%. A subset (n=1780) from VIP was used in paper II for the circ-annual leptin analysis, and VIP data linked to the diabetes register in Västerbotten (DiabNorr) were used in a case referent study (640 patients with T2DM) in paper III. The Mauritius Non-Communicable Disease Study was performed in 1987 in 10 randomly selected (with probability proportional to size) population clusters. All eligible adults ages 25–74 years were invited, and the participation rate was 86% (n=5083). In 1992, a follow-up survey was performed in 49% of the initial participants. The Mauritius survey data were used in paper II. Results I. BMI increased in men ages 25–74 years and in women ages 25–44 years in northern Sweden between 1986 and 2004. The prevalence of obesity (BMI 30) increased in men ages 25–44 and 55–74 years and in women ages 25–44 years. The prevalence of obesity increased from 10.4% to 19.1% in men and from 12.9% to 17.9% in women ages 25–64 years. Waist circumference (WC) decreased in women of all ages and in men ages 55–64 years between 1986 and 1990. After 1990, WC increased again, and the prevalence of abdominal obesity rose markedly in women ages 25–64 years. II. Differences in circulating levels of leptin, leptin per BMI unit (leptin/BMI), and leptin per cm in WC (leptin/waist) were tested in men and women of Asian Indian, Creole (African), and Caucasian ethnicity. Asian Indian men and women had the highest leptin concentrations and Caucasian men and women the lowest while Creole men and women had intermediate values for leptin, leptin/BMI, and leptin/waist. No circ-annual variation in leptin concentrations was seen in Caucasians. The intra-individual test– retest stability for leptin was equal in men and women of different ethnicities, over 5–13 years, with an intra-class correlation of 0.65–0.82. III. High adiponectin concentrations predicted decreased risk of T2DM in both insulin-sensitive and insulin-resistant men and women, whereas high leptin levels predicted increased risk for T2DM only in insulinsensitive men. A high leptin–adiponectin ratio predicted T2DM in both men and women, and men with a high ratio had a shorter time to diagnosis than those with a low ratio. IV. In northern Sweden, fasting and post-load glucose increased in women ages 24–65 years with 0.2 mmol/l and 0.7 mmol/l, respectively, between 1990 and 2009. Consequently, the prevalence of impaired fasting glucose and impaired glucose tolerance (IGT) rose from 4.5% to 7.7%, and from 7.8% to 14.5%, respectively. In men, post-load glucose increased at 0.5 mmol/l, and the prevalence of IGT rose from 3.5% to 10.1%. The prevalence of diabetes did not increase. An independent relationship between leptin and changes in fasting and post-load glucose was seen in men but not in women. Conclusion An increasing obesity and concomitant deterioration in glucose metabolism was seen in northern Sweden in the period studied. High adiponectin concentrations predicted a decreased risk of T2DM in both men and women, whereas high leptin concentrations predicted an increase in fasting and post-load glucose as well as an increased risk of T2DM in men but not in women. Individual insulin resistance status modified the association between leptin and T2DM, and the leptin–adiponectin ratio may add further predictive information beyond the measures of the separate hormones. In relation to traditional anthropometric measures of obesity, Asian Indian men and women had the highest and Caucasians the lowest concentrations of leptin while Creole (African) men and women had intermediate levels. As a risk marker, leptin has a high intra-individual stability, equal in men and women and among different ethnicities over 5–13 years with no circ-annual variation.
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| 2. |
- Lundqvist, Gunnar, 1945-
(författare)
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Tobaksvanor i medelåldern : riskfaktormönster, rökstoppsattityder och erfarenheter av att sluta röka
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tobacco use, mostly smoking, has been a deeply rooted habit for many people for centuries. However, it was not until the second half of last century that the risks with smoking became obvious. Today when the bad consequences of smoking are recognized by almost all people, it is important to discuss why smokers choose to continue smoking. The main aim of this thesis is to try to better explain why some middle aged smokers choose to continue smoking in spite of knowledge of the huge mass of information that is gathered about the serious side effects of smoking. Many of these people cannot by any means stop smoking while others succeed in their attempt to quit. Since 1990 all inhabitants in Västerbotten County are invited to a health survey the year they become 40, 50 and 60 years: the Västerbotten Intervention Programme (VIP). The VIP health survey consists of risk markers for cardiovascular diseases (blood pressure, blood sugar and blood lipids), a questionnaire on socioeconomic, psychosocial and life style factors, supplemented by a health counselling discussion with a district nurse. The thesis is based on five papers. Four of them use VIP data. In Paper I tobacco habits are related to different levels of age, gender and education and are analyzed in a 18 year perspective, based on 112 920 VIP participants. As it has been suggested that women might have more difficulties than men to stop smoking, Paper II elucidates women’s perceptions about smoking, based on interviews with nine smoking and ex-smoking women. Paper III identify metabolic consequences of heavy smoking and relate these to social and life style factors that might accompany smoking behaviour. Paper IV analyzes the individual pattern of changes in tobacco use over a ten year period among 16 492 subjects, while Paper V, a questionnaire study, addresses 513 respondents own assessments of what was especially important for them in their attempts to become smoke-free and what was positive and what was negative when they stopped to smoke. Their knowledge and attitudes about smoking issues were also analyzed. The thesis shows that heavy smokers seem to have a metabolic profile heading towards the metabolic syndrome, and that this pattern could be reinforced by some social and life style factors. Smoking women expressed their concern over weight gain, if quitting. They provided a series of different hinders and barriers against smoking cessation as well as some explanations of why it was reasonable to continue smoking. Feeling of shame and fatalism played a major role but also influence from friends, relatives and media was regarded as important factors. For both men and women the decision to quit smoking was supported from relatives and from a wish for a healthier lifestyle. Support from the health care providers was perceived to be rare. Snus use and nicotine replacement therapy in the attempts to stop smoking were also discussed. In summary the thesis stresses that the use of tobacco products in Västerbotten is slowly decreasing in the middle aged population in general. For people with shorter school education and at somewhat younger age the dual use of tobacco products, cigarettes and snus, are slowly increasing. However, after ten years, half of the smokers in these age cohorts still smoke. It is possible that the more addicted smokers remain, why a major challenge is to find new ways to support these individuals. Health care providers have to do more, but also schools, media, societal organizations and governmental bodies on local, regional and national levels. One proposal is to look upon nicotine dependence, especially smoking, as a chronic condition that needs various multifactorial treatment and long time follow up, and that it is important to organize the support accordingly. Special antitobacco or life style centres outside the established health care organization where focus could be on different healthy life style matters is suggested. The thesis also suggest different ways to handle smoking cessation at the primary health care level.
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