Type 1 and type 2 diabetes among young adults in Finland : Incidence and perinatal exposures

This study aimed to examine the incidence of young adult-onset T1DM and T2DM among Finns, and to explore the possible risk factors for young adult-onset T1DM and T2DM that occur during the perinatal period and childhood. In the studies I-II, the incidence of diabetes was examined among 15-39-year-old Finns during the years 1992-2001. Information on the new diagnoses of diabetes was collected from four sources: standardized national reports filled in by diabetes nurses, the Hospital Discharge Register, the Drug Reimbursement Register, and the Drug Prescription Register. The type of diabetes was assigned using information obtained from these four data sources. The incidence of T1DM was 18 per 100,000/year, and there was a clear male predominance in the incidence of T1DM. The incidence of T1DM increased on average 3.9% per year during 1992-2001. The incidence of T2DM was 13 per 100,000/year, and it displayed an increase of 4.3% per year. In the studies III-V, the effects of perinatal exposures and childhood growth on the risk for young adult-onset T1DM and T2DM were explored in a case-control setting. Individuals diagnosed with T1DM (n=1,388) and T2DM (n=1,121) during the period 1992-1996 were chosen as the diabetes cases for the study, and two controls were chosen for each case from the National Population Register. Data on the study subjects parents and siblings was obtained from the National Population Register. The study subjects original birth records and child welfare clinic records were traced nationwide. The risk for young adult-onset T2DM was the lowest among the offspring of mothers aged about 30 years, whereas the risk for T2DM increased towards younger and older maternal ages. Birth orders second to fourth were found protective of T2DM. In addition, the risk for T2DM was observed to decrease with increasing birth weight until 4.2 kg, after which the risk began to increase. A high body mass index (BMI) at the BMI rebound between ages 3-11 years substantially increased the risk for T2DM, and the excess weight gain in individuals diagnosed with T2DM began in early childhood. Maternal age, birth order, or body size at birth had no effect on the risk for young adult-onset T1DM. Instead, individuals with T1DM were observed to have a higher maximum BMI before the age of 3 than their control subjects. In conclusion, the increasing trend in the development of both T1DM and T2DM among young Finnish adults is alarming. The high risk for T1DM among the Finnish population extends to at least 40 years of age, and at least 200-300 young Finnish adults are diagnosed with T2DM every year. Growth during the fetal period and childhood notably affects the risk for T2DM. T2DM prevention should also target childhood obesity. Rapid growth during the first years of life may be a risk factor for late-onset T1DM.

Early Growth and Later Health, Focus on Metabolic Syndrome, Obesity and Physical Activity

The Developmental Origins of Health and Disease Hypothesis proposes that adverse health outcomes in adult life are in part programmed during fetal life and infancy. This means that e.g. restricted nutrition during pregnancy programmes the offspring to store fat more effectively, to develop faster and to reach puberty earlier. These adaptations are beneficial in terms of short term survival. However, in developed countries these adaptations often lead to an increased risk of obesity and metabolic disturbances in later life, due to a mismatch between the prenatal and postnatal environment. This thesis aimed to study the role of early growth in people who are obese as adults, but metabolically healthy as well as in those who are normal in weight but metabolically obese. Other study aims were to assess whether physical activity and cardiorespiratory fitness are programmed early in life. The role of socioeconomic status in the development of obesity from a life course setting was also studied. These studies included 2003 men and women born in Helsinki between 1934 and 1944 with detailed information of their prenatal and childhood growth as well as living conditions. They participated in the detailed clinical examination during the years 2001-2004. A sub-group of the subjects participated in the UKK Institute 2-kilometre walk test. Metabolic syndrome was defined according to the 2005 criteria of the International Diabetes Federation. Among the obese men and women 20 % were metabolically healthy. Those with metabolic syndrome did not differ in birth size compared to the healthy ones, but by two years of age, they were lighter and thinner, and remained so up to 11 years. The period when changes in BMIs were predictive of the metabolic syndrome was from birth to 7 years. Of the normal weight individuals 17 % were metabolically obese. Again, there were no differences in birth size. However, by the age 7 years, those men who later developed metabolic syndrome were thinner. Gains in BMI during the first two years of life were protective of the syndrome. Children who were heavier, and especially taller, were more physically active, exercised with higher intensity and had higher cardiorespiratory fitness in their adult life than those who were shorter and thinner as children. Lower educational attainment and lower adult social class were associated with obesity in both men and women. Childhood social class was inversely associated with body mass index only in men while lower household income was associated with higher BMI in women. These results support the role of early life factors in the development of metabolic syndrome and adult life style. Early detection of risk factors predisposing to these conditions is highly relevant from a public health point of view.

Childhood and adolescent antecedents of work stress and early atherosclerosis

Work stress is after musculoskeletal disorders the second most common work-related health problem in the European Union, affecting 28% of EU employees. Furthermore, a 50% excessive cardiovascular disease risk among employees with work stress is reported. High job demands combined with low job control according to the Job Demands-Job Control model, or high effort combined with low rewards according to Effort-Reward Imbalance model, are likely to produce work stress in the majority of employees. Atherosclerotic wall thickening is a validated marker of an increased risk of cardiovascular disease. This study examined the role of childhood and adolescent factors as antecedents of work stress and early atherosclerosis, and in the relationship between them. The Cardiovascular Risk in Young Finns Study, (the CRYF project) started in 1980 when the participants were at the age of three to 18 years. Follow-ups have been conducted every three years until 1992, after that in 1997 and 2001, and the latest is ongoing in 2008. The participants parents reported their socioeconomic position in 1980 and 1983, and their life satisfaction in 1983. Biological risk factors were measured in 1980 and 2001. Type A behaviour was reported in 1986, 1989 and 2001. In the 2001 follow-up when the participants were aged 24 to 39, work stress was assessed from responses to questionnaires on job demands-job control and effort-reward imbalance, and education. Ultrasound measurement of the carotid intima-media thickness (CIMT) was used to assess atherosclerosis. There were 755, 746, 1014 and 494 participants in studies I-IV, respectively. The results showed that low parental socioeconomic position and parental life dissatisfaction during childhood and adolescence predicted higher levels of job strain 18 years later, and that education mediated the relationship between parental socioeconomic position and job strain. Childhood and adolescent family factors were not related to the effort-reward imbalance. Parental life satisfaction was associated with high rewards at work among the men, and high parental socioeconomic position was associated with high reward among the women. Among the men, the eagerness-energy component of Type A behaviour across different developmental periods predicted increased CIMT. Among the women, hard-driving component of Type A behaviour predicted decreased CIMT. Low leadership characteristic in adolescence and early adulthood was associated with both high job strain and increased CIMT, and attenuated the relationship between job strain and CIMT to non-significance in men. The current findings add to the literature on the relationship between job strain and health literature in adopting a developmental perspective. The results imply that work stress does not completely originate from work. There are childhood and adolescent environmental and dispositional effects on work stress and CIMT several years later, and these partly seem to operate through educational attainment.

Self-rating scales in the assessment of current and childhood symptoms of attention deficit hyperactivity disorder in adults

Objective: Attention deficit hyperactivity disorder (ADHD) is a life-long condition, but because of its historical status as a self-remitting disorder of childhood, empirically validated and reliable methods for the assessment of adults are scarce. In this study, the validity and reliability of the Wender Utah Rating Scale (WURS) and the Adult Problem Questionnaire (APQ), which survey childhood and current symptoms of ADHD, respectively, were studied in a Finnish sample. Methods: The self-rating scales were administered to adults with an ADHD diagnosis (n = 38), healthy control participants (n = 41), and adults diagnosed with dyslexia (n = 37). Items of the self-rating scales were subjected to factor analyses, after which the reliability and discriminatory power of the subscales, derived from the factors, were examined. The effects of group and gender on the subscales of both rating scales were studied. Additionally, the effect of age on the subscales of the WURS was investigated. Finally, the diagnostic accuracy of the total scores was studied. Results: On the basis of the factor analyses, a four-factor structure for the WURS and five-factor structure for the APQ had the best fit to the data. All of the subscales of the APQ and three of the WURS achieved sufficient reliability. The ADHD group had the highest scores on all of the subscales of the APQ, whereas two of the subscales of the WURS did not statistically differ between the ADHD and the Dyslexia group. None of the subscales of the WURS or the APQ was associated with the participant's gender. However, one subscale of the WURS describing dysthymia was positively correlated with the participant's age. With the WURS, the probability of a correct positive classification was .59 in the current sample and .21 when the relatively low prevalence of adult ADHD was taken into account. The probabilities of correct positive classifications with the APQ were .71 and .23, respectively. Conclusions: The WURS and the APQ can provide accurate and reliable information of childhood and adult ADHD symptoms, given some important constraints. Classifications made on the basis of the total scores are reliable predictors of ADHD diagnosis only in populations with a high proportion of ADHD and a low proportion of other similar disorders. The subscale scores can provide detailed information of an individual's symptoms if the characteristics and limitations of each domain are taken into account. Improvements are suggested for two subscales of the WURS.

Effects of dairy proteins and calcium on diet-induced obesity in mice

Diet high in dairy products is inversely associated with body mass index, risk of metabolic syndrome and prevalence of type 2 diabetes in several populations. Also a number of intervention studies support the role of increased dairy intake in the prevention and treatment of obesity. Dairy calcium has been suggested to account for the effect of dairy on body weight, but it has been repeatedly shown that the effect of dairy is superior to the effect of supplemental calcium. Dairy proteins are postulated to either enhance the effect of calcium or have an independent effect on body weight, but studies in the area are scarce. The aim of this study was to evaluate the potential of dairy proteins and calcium in the prevention and treatment of diet-induced obesity in C57Bl/6J mice. The effect of dairy proteins and calcium on the liver and adipose tissue was also investigated in order to characterise the potential mechanisms explaining the reduction of risk for metabolic syndrome and type 2 diabetes. A high-calcium diet (1.8%) in combination with dietary whey protein inhibited body weight and fat gain and accelerated body weight and fat loss in high-fat-fed C57Bl/6J mice during long-term studies of 14 to 21 weeks. α-lactalbumin, one of the major whey proteins, was the most effective whey protein fraction showing significantly accelerated weight and fat loss during energy restriction and reduced the amount of visceral fat gain during ad libitum feeding after weight loss. The microarray data suggest sensitisation of insulin signalling in the adipose tissue as a result of a calcium-rich whey protein diet. Lipidomic analysis revealed that weight loss on whey protein-based high-calcium diet was characterised by significant decreases in diabetogenic diacylglycerols and lipotoxic ceramide species. The calcium supplementation led to a small, but statistically significant decrease in fat absorption independent of the protein source of the diet. This augments, but does not fully explain the effects of the studied diets on body weight. A whey protein-containing high-calcium diet had a protective effect against a high-fat diet-induced decline of β3 adrenergic receptor expression in adipose tissue. In addition, a high-calcium diet with whey protein increased the adipose tissue leptin expression which is decreased in this obesity-prone mouse strain. These changes are likely to contribute to the inhibition of weight gain. The potential sensitisation of insulin signalling in adipose tissue together with the less lipotoxic and diabetogenic hepatic lipid profile suggest a novel mechanistic link to explain why increased dairy intake is associated with a lower prevalence of metabolic syndrome and type 2 diabetes in epidemiological studies. Taken together, the intake of a high-calcium diet with dairy proteins has a body weight lowering effect in high-fat-fed C57Bl/6J mice. High-calcium diets containing whey protein prevent weight gain and enhance weight loss, α-lactalbumin being the most effective whey protein fraction. Whey proteins and calcium have also beneficial effects on hepatic lipid profile and adipose tissue gene expression, which suggest a novel mechanistic link to explain the epidemiological findings on dairy intake and metabolic syndrome. The clinical relevance of these findings and the precise mechanisms of action remain an intriguing field of future research.

Early Childhood Caries and a Community Trial of its Prevention in Tehran, Iran

Varhaislapsuuden karies ja sen ehkäisy kehittyvän terveydenhuollon maassa Varhaislapsuuden karies on merkittävä kansanterveysongelma varsinkin lapsirikkaissa maissa ja väestöissä. Karieksen hoitaminen vie paljon voimavaroja ja aiheuttaa mittavia taloudellisia seuraamuksia. Karies voi ilmaantua lapselle jo vauvaikäisenä, pian ensimmäisten maitohampaiden puhjettua suuhun. Alle 3-vuotiaiden karieksesta on kuitenkin niukasti tilastotietoja. Maailman terveysjärjestökin suosittaa tietojen keräämistä vasta 3-vuotiaiden ikäryhmästä. Heistä kariesta sairastaa Suomessa 16 %, Yhdysvalloissa 25 %, Englannissa 30 %, Iranissa 46 % ja Saudi-Arabiassa 61 %. Tämä väitöstutkimus selvitti karieksen esiintymistä ja sen vaaratekijöitä 1─3-vuotiailla Teheranissa. Lisäksi tutkimus arvioi perusterveydenhuoltoon sisällytetyn karieksen ehkäisyn tuloksellisuutta. Tutkimuskohteiksi arvottiin Teheranista 18 neuvolaa. Jokaisessa oltiin 4 päivää, jolloin kaikkia rokotuksiin tulleita 1─3-vuotiaita äiteineen pyydettiin osallistumaan tutkimukseen. Kahta lukuun ottamatta kaikki äidit suostuivat, ja aineistoon tuli kaikkiaan 504 lasta äiteineen. Kaikki 1-vuotiaat, 242 lasta äiteineen, valittiin karieksen ehkäisykokeiluun. Sitä varten neuvolat jaettiin kolmeen ryhmään, joista kaksi (A ja B) oli koeryhmiä ja yksi (C) oli vertailuryhmä. Tutkimus alkoi äidin haastattelulla. Siinä selvitettiin perheen koulutus- ja tulotaso sekä lapsen ruokinnasta imetyksen kesto, yösyötöt ja päiväaikaan nautitut makeat. Vielä kysyttiin lapsen ja äidin suuhygieniatavoista ja äidin kokemuksista lapsen suun puhdistamisessa. Sitten hammaslääkäri tutki lapsen suun ja kirjasi karieksen ja hammasplakin esiintymät. Suun tutkimuksen jälkeen äiti ja lapsi siirtyivät rokotushuoneeseen. Koeryhmissä (A ja B) äidit saivat terveydenhoitajalta suunterveyttä koskevan esitteen ja kehotuksen lukea se huolellisesti. Lisäksi ryhmässä A terveydenhoitaja kertoi suun ja hampaiden terveydenhoidosta saman esitteen avulla, ja neuvolan henkilökunta muistutti suunhoidon tärkeydestä puhelimitse kahdesti seuraavan puolen vuoden kuluessa. Vertailuryhmässä äideille ei annettu suunhoidon ohjeita. Kaikissa ryhmissä äitejä muistutettiin seuraavan rokotuskerran ajankohdasta, muttei mainittu tulevaa toista hammastarkastusta. Varhaislapsuuden kariesta sairasti ikäryhmästä riippuen 3─26 % tutkituista 1─3-vuotiaista, ja 65─76 %:lla oli hammasplakkia. Äideistä 68 % harjasi hampaansa päivittäin ja 39 % puhdisti lapsensa suun päivittäin. Mitä useammin äiti harjasi omat hampaansa, sitä paremmin hän huolehti lapsen suun puhtaudesta. Rintaruokinta oli yleistä eikä lisännyt kariesvaaraa. Yöllä pullomaitoa saavilla karies oli 5 kertaa yleisempää kuin muilla. Neuvolassa saatu ohjeistus ehkäisi selvästi karieksen syntyä puolen vuoden kokeessa.

Predictors of disability retirement: From early intentions to retirement

The strong tendency of elderly employees to retire early and the simultaneous aging of the population have been major topics of policy and scientific debate. A key concern has been the financing of future pension schemes and possible labour shortage, especially in social and health services within the public sector. The aging of the population is inevitable, but efforts can be made to prevent or postpone early exit from the labour force, e.g., by identifying and intervening in the factors that contribute to the process of early retirement due to disability. The associations of intentions to retire early, poor mental health and different psychosocial factors with the process of disability retirement are still poorly understood. The purpose of this study was to investigate the associations of intentions to retire early, poor mental health, work and family related psychosocial factors and experiences of earlier life stages with the process of disability retirement. The data were derived from the Helsinki Health Study (HHS, N=8960) and the Health and Social Support Study (HeSSup, N=25 901). The Helsinki Health Study is an ongoing employee cohort study among middle-aged women and men. The Health and Social Support Study is an ongoing longitudinal study of a working-age sample representative of the Finnish population. The analyses were restricted to respondents 40 years of age or older. Age and gender adjusted prevalence and incidence rates were calculated. Associations were studied by using logistic, multinomial and Cox regression. Strong intentions to retire early were common among employees. Poor mental health, unfavourable working conditions and work-to-family conflicts were clearly associated with increased intentions to retire early. Strong intentions to retire early predicted disability retirement. Risk of disability retirement increased in a dose-response manner with increasing number of childhood adversities. Poor mental and somatic health, life dissatisfaction, heavy alcohol consumption, current smoking, obesity and low socioeconomic status were also predictors of disability retirement. The impact of poor mental health and adverse experiences from earlier life stages, work and family related psychosocial factors, e.g., work-family interface, the subjective experience of well-being and health related risk behaviours on the process of disability retirement should be recognised. Preventive measures against disability retirement should be launched before subjective experience of ill health, work disability and strong intentions to retire early emerge.

Obesity, Smoking and Dieting

Lihavuus ja ylipaino ovat viime vuosikymmeninä yleistyneet; jo yli puolet länsimaiden väestöstä on ylipainoisia ja viidennes lihavia. Varsinkin nuorilla ylipainon lisääntyminen on ollut nopeaa. Ylipaino, erityisesti yhdistettynä vyötärölihavuuteen, sekä tupakointi lisäävät sairastavuutta sydän- ja verisuonisairauksiin, metabolisiin sairauksiin, kuten diabetekseen, sekä moniin syöpiin. Lihavuus ja tupakointi ovatkin kehittyneiden maiden tärkeimpiä ehkäistävissä olevia kuolinsyitä. Samanaikaisesti ylipainon kanssa laihduttaminen ja jopa terveydelle haitalliset laihdutusmenetelmät, kuten tupakointi painonhallintakeinona on tullut yhä yleisemmäksi. Nopeaan painonpudotukseen tähtäävällä laihduttamisella on usein terveydelle haitallisia seurauksia kuten painon nousu yli alkuperäisen painon ja kehon rasvajakauman muuttuminen epäterveellisemmäksi. Kolme neljännestä merkittävästi laihduttaneista kertoo painon nousseen takaisin. Tupakoinnin ja toistuvan laihduttamisen vaikutukset ylipainon ja lihavuuden kehittymiselle kytkeytyvät toisiinsa. Tässä väitöskirjatyössä tutkittiin toistuvan laihduttamisen ja tupakoinnin vaikutusta kehon painoon ja lisäksi tupakoinnin vaikutusta vyötärölihavuuden kehittymiseen. Työn toisena tavoitteena oli tutkia, kuinka voimakkaasti tupakointi ja toistuva laihduttaminen liittyvät toisiinsa suomalaisilla ja onko tämä yhteys erilainen eri ikäryhmissä ja sukupuolilla. Työ perustuu kolmeen laajaan kyselyaineistoon: Nuorten Kaksosten Terveystutkimuksen (englanniksi FinnTwin16) aineistossa on seurattu 1975-79 syntyneitä kaksosia 16, 17, 18 ja 24 vuoden ikäisinä (N=5563). Suomen kaksoskohortin aineisto (N= 12 793) on kerätty vuonna 1990 samaa sukupuolta olevilta, vuosina 1930-57 syntyneiltä kaksosilta. Entisten huippu-urheilijoiden (N=1838) ja heille kaltaistettujen verrokkien (N=834) seurantatutkimuksessa tiedot on kerätty vuosina 1985, 1995 ja 2001. Pituus, paino ja tupakointi on kysytty kaikissa kyselyissä. Kaksoset vastasivat laihdutuskäyttäytymistä koskeviin kysymyksiin. Urheilijoiden laihdutuskäyttäytyminen pääteltiin lajin perusteella, sillä toistuvan laihduttamisen tiedetään olevan yleistä painoluokissa urheilevilla urheilijoilla (esim.painijat, nyrkkeilijät). Nuoruusiän tupakointi ennusti vyötärölihavuutta molemmilla sukupuolilla ja lisäksi ylipainoisuutta naisilla. Toistuva laihduttaminen oli yhteydessä myöhempään painonnousuun ja lihavuuteen miehillä. Lisäksi toistuvan laihduttamisen ja tupakoinnin todettiin liittyvän toisiinsa nuorilla aikuisilla. Vanhemmissa ikäluokissa miehet, jotka tupakoivat, laihduttivat harvemmin kuin tupakoimattomat. Lihavuuteen ja vyötärölihavuuteen liittyvän oheissairastavuuden ennaltaehkäisyssä tupakoinnin ja toistuvan laihduttamisen vähentäminen saattavat olla aiemmin luultua tehokkaampia keinoja.

Anthropometric measures of obesity-their association with type 2 diabetes and hypertension across ethnic groups

Clinical trials have shown that weight reduction with lifestyles can delay or prevent diabetes and reduce blood pressure. An appropriate definition of obesity using anthropometric measures is useful in predicting diabetes and hypertension at the population level. However, there is debate on which of the measures of obesity is best or most strongly associated with diabetes and hypertension and on what are the optimal cut-off values for body mass index (BMI) and waist circumference (WC) in this regard. The aims of the study were 1) to compare the strength of the association for undiagnosed or newly diagnosed diabetes (or hypertension) with anthropometric measures of obesity in people of Asian origin, 2) to detect ethnic differences in the association of undiagnosed diabetes with obesity, 3) to identify ethnic- and sex-specific change point values of BMI and WC for changes in the prevalence of diabetes and 4) to evaluate the ethnic-specific WC cutoff values proposed by the International Diabetes Federation (IDF) in 2005 for central obesity. The study population comprised 28 435 men and 35 198 women, ≥ 25 years of age, from 39 cohorts participating in the DECODA and DECODE studies, including 5 Asian Indian (n = 13 537), 3 Mauritian Indian (n = 4505) and Mauritian Creole (n = 1075), 8 Chinese (n =10 801), 1 Filipino (n = 3841), 7 Japanese (n = 7934), 1 Mongolian (n = 1991), and 14 European (n = 20 979) studies. The prevalence of diabetes, hypertension and central obesity was estimated, using descriptive statistics, and the differences were determined with the χ2 test. The odds ratios (ORs) or  coefficients (from the logistic model) and hazard ratios (HRs, from the Cox model to interval censored data) for BMI, WC, waist-to-hip ratio (WHR), and waist-to-stature ratio (WSR) were estimated for diabetes and hypertension. The differences between BMI and WC, WHR or WSR were compared, applying paired homogeneity tests (Wald statistics with 1 df). Hierarchical three-level Bayesian change point analysis, adjusting for age, was applied to identify the most likely cut-off/change point values for BMI and WC in association with previously undiagnosed diabetes. The ORs for diabetes in men (women) with BMI, WC, WHR and WSR were 1.52 (1.59), 1.54 (1.70), 1.53 (1.50) and 1.62 (1.70), respectively and the corresponding ORs for hypertension were 1.68 (1.55), 1.66 (1.51), 1.45 (1.28) and 1.63 (1.50). For diabetes the OR for BMI did not differ from that for WC or WHR, but was lower than that for WSR (p = 0.001) in men while in women the ORs were higher for WC and WSR than for BMI (both p < 0.05). Hypertension was more strongly associated with BMI than with WHR in men (p < 0.001) and most strongly with BMI than with WHR (p < 0.001), WSR (p < 0.01) and WC (p < 0.05) in women. The HRs for incidence of diabetes and hypertension did not differ between BMI and the other three central obesity measures in Mauritian Indians and Mauritian Creoles during follow-ups of 5, 6 and 11 years. The prevalence of diabetes was highest in Asian Indians, lowest in Europeans and intermediate in others, given the same BMI or WC category. The  coefficients for diabetes in BMI (kg/m2) were (men/women): 0.34/0.28, 0.41/0.43, 0.42/0.61, 0.36/0.59 and 0.33/0.49 for Asian Indian, Chinese, Japanese, Mauritian Indian and European (overall homogeneity test: p > 0.05 in men and p < 0.001 in women). Similar results were obtained in WC (cm). Asian Indian women had lower  coefficients than women of other ethnicities. The change points for BMI were 29.5, 25.6, 24.0, 24.0 and 21.5 in men and 29.4, 25.2, 24.9, 25.3 and 22.5 (kg/m2) in women of European, Chinese, Mauritian Indian, Japanese, and Asian Indian descent. The change points for WC were 100, 85, 79 and 82 cm in men and 91, 82, 82 and 76 cm in women of European, Chinese, Mauritian Indian, and Asian Indian. The prevalence of central obesity using the 2005 IDF definition was higher in Japanese men but lower in Japanese women than in their Asian counterparts. The prevalence of central obesity was 52 times higher in Japanese men but 0.8 times lower in Japanese women compared to the National Cholesterol Education Programme definition. The findings suggest that both BMI and WC predicted diabetes and hypertension equally well in all ethnic groups. At the same BMI or WC level, the prevalence of diabetes was highest in Asian Indians, lowest in Europeans and intermediate in others. Ethnic- and sex-specific change points of BMI and WC should be considered in setting diagnostic criteria for obesity to detect undiagnosed or newly diagnosed diabetes.

Leisure activities and obesity in adolescence : a follow-up study among twins

The aims of this dissertation were 1) to investigate associations of weight status of adolescents with leisure activities, and computer and cell phone use, and 2) to investigate environmental and genetic influences on body mass index (BMI) during adolescence. Finnish twins born in 1983–1987 responded to postal questionnaires at the ages of 11-12 (5184 participants), 14 (4643 participants), and 17 years (4168 participants). Information was obtained on weight and height, leisure activities including television viewing, video viewing, computer games, listening to music, board games, musical instrument playing, reading, arts, crafts, socializing, clubs, sports, and outdoor activities, as well as computer and cell phone use. Activity patterns were studied using latent class analysis. The relationship between leisure activities and weight status was investigated using logistic and linear regression. Genetic and environmental effects on BMI were studied using twin modeling. Of individual leisure activities, sports were associated with decreased overweight risk among boys in both cross-sectional and longitudinal analyses, but among girls only cross-sectionally. Many sedentary leisure activities, such as video viewing (boys/girls), arts (boys), listening to music (boys), crafts (girls), and board games (girls), had positive associations with being overweight. Computer use was associated with a higher prevalence of overweight in cross-sectional analyses. However, musical instrument playing, commonly considered as a sedentary activity, was associated with a decreased overweight risk among boys. Four patterns of leisure activities were found: ‘Active and sociable’, ‘Active but less sociable’, ‘Passive but sociable’, and ‘Passive and solitary’. The prevalence of overweight was generally highest among the ‘Passive and solitary’ adolescents. Overall, leisure activity patterns did not predict overweight risk later in adolescence. An exception were 14-year-old ‘Passive and solitary’ girls who had the greatest risk of becoming overweight by 17 years of age. Heritability of BMI was high (0.58-0.83). Common environmental factors shared by family-members affected the BMI at 11-12 and 14 years but their effect had disappeared by 17 years of age. Additive genetic factors explained 90-96% of the BMI stability across adolescence. Genetic correlations across adolescence were high, which suggests similar genetic effects on BMI throughout adolescence, while unique environmental effects on BMI appeared to vary. These findings suggest that family-based interventions hold promise for obesity prevention into early and middle adolescence, but that later in adolescence obesity prevention should focus on individuals. A useful target could be adolescents' leisure time, and our findings highlight the importance of versatility in leisure activities.