Age, period and birth cohort effects on prevalence of overweight and obesity in Australian adults from 1990 to 2000

Age-period-cohort analysis for trends in body mass index in Ireland

Background

Obesity is a growing problem worldwide and can often result in a variety of negative health outcomes. In this study we aim to apply partial least squares (PLS) methodology to estimate the separate effects of age, period and cohort on the trends in obesity as measured by body mass index (BMI).

Methods

Using PLS we will obtain gender specific linear effects of age, period and cohort on obesity. We also explore and model nonlinear relationships of BMI with age, period and cohort. We analysed the results from 7,796 men and 10,220 women collected through the SLAN (Surveys of Lifestyle, attitudes and Nutrition) in Ireland in the years 1998, 2002 and 2007.

Results

PLS analysis revealed a positive period effect over the years. Additionally, men born later tended to have lower BMI (−0.026 kg·m^-2 yr^-1, 95% CI: -0.030 to −0.024) and older men had in general higher BMI (0.029 kg·m^-2 yr^-1, 95% CI: 0.026 to 0.033). Similarly for women, those born later had lower BMI (−0.025 kg·m^-2 yr^-1, 95% CI: -0.029 to −0.022) and older women in general had higher BMI (0.029 kg·m^-2 yr^-1, 95% CI: 0.025 to 0.033). Nonlinear analyses revealed that BMI has a substantial curvilinear relationship with age, though less so with birth cohort.

Conclusion

We notice a generally positive age and period effect but a slightly negative cohort effect. Knowing this, we have a better understanding of the different risk groups which allows for effective public intervention measures to be designed and targeted for these specific population subgroups.

Validity and reproducibility of a food frequency questionnaire as a measure of recent dietary intake in young adults

This research assessed the relative validity and reproducibility of the Dietary Questionnaire for Epidemiological Studies (DQESV2) over one month in young adults, given the lack of concise and convenient instruments for assessing recent dietary intake in this population. Participants were recruited from a large Australian university (N = 102; 35% male; age 18–34 years; body mass index 16–37 kg/m²). Five one-day weighed food records (WFR) were administered over one month followed by the DQESV2. Estimates for nutrients (energy, protein, total fat, saturated fat, carbohydrate, sugars, dietary fibre, and alcohol) and fruit and vegetable servings were compared between methods using correlation coefficients, 95% limits of agreement, and quintile classifications. One week later, a second DQESV2 was completed by n = 77 of the participants to assess reproducibility using intra-class correlations (ICC) and weighted kappa. Comparing methods, all nutrients and fruit and vegetable servings showed significant positive correlations (P<0.05) except protein intake in males; over 60% of participants were within one quintile classification except total fat and dietary fibre intakes in males (55% and 56%, respectively); and differences in nutrient and food intakes between methods were all within +/−20% of the mean WFR values except alcohol intake in females. Between first and second administrations of the DQESV2 all ICC coefficients were positive (P<0.01) and weighted kappa coefficients ranged from 0.54 for fruit servings (including fruit juice) in males to 0.91 for protein intake in females. Over a one month period, the DQESV2 demonstrated good reproducibility for the studied nutrients and for fruit and vegetable servings and provided a valid measure of the studied nutrients, except alcohol in females, and of fruit servings (including fruit juice) in both genders, at the group level in this young adult population.

A mobile health intervention for weight management among young adults: a pilot randomised controlled trial

BACKGROUND

Today's generation of young adults are gaining weight faster than their parents; however, there remains insufficient evidence to inform interventions to prevent this weight gain. Mobile phones are a popular means of communication that may provide a convenient, inexpensive means to deliver health intervention programmes. This pilot study aimed to measure the effect of a 12-week mobile health (mHealth) intervention on body weight, body mass index and specific lifestyle behaviours addressed by the programme.

METHODS

University students and staff aged 18-35 years (n = 51) were randomised (ratio 1 : 1, intervention : control). Both groups received a printed diet booklet with instructions prepared by a dietitian. The intervention group also received Short Message Service (SMS) text messages (four per week), e-mails (four per week), and had access to smartphone applications and Internet forums.

RESULTS

Pre- to post-intervention, participants in the intervention group decreased their body weight [mean (SD)] [-1.6 (2.6) kg], increased their light intensity activity [34 (35) min day(-1)] and reported an increased vegetable (1.0 median serving day(-1)) and decreased sugar-sweetened beverage intake [-355 (836) mL week(-1)]. Despite this, post-intervention changes in outcomes were not significantly different from controls.

CONCLUSIONS

The piloted mHealth programme provided some short-term positive changes in weight, nutrition and physical activity using a low cost, convenient delivery method for this population. However, changes were no different from those observed among controls. This might partly be explained by intervention participants' low engagement with the programme, which is likely to require further modification to provide more regular, personalised, monitored support.

Birth cohort effects on abdominal obesity in the United States: the Silent Generation, Baby Boomers and Generation X

BACKGROUND

Abdominal obesity predicts a wide range of adverse health outcomes. Over the past several decades, prevalence of abdominal obesity has increased markedly in industrialized countries like the United States No previous analyses, however, have evaluated whether there are birth cohort effects for abdominal obesity. Estimating cohort effects is necessary to forecast future health trends and understand the past population-level trends.

METHODS

This analysis evaluated whether there were birth cohort effects for abdominal obesity for the Silent Generation (born 1925-1945), children of the Great Depression; Baby Boomers (born 1946-1964); or Generation X (born 1965-1980). Cohort effects for prevalence of abdominal obesity were estimated using the median polish method with data collected from the National Health and Nutrition Examination Survey (NHANES) between 1988 and 2008. Respondents were aged 20-74 years.

RESULTS

After taking into account age effects and ubiquitous secular changes, the Silent Generation and Generation X had higher cohort-specific prevalence of abdominal obesity than the Baby Boomers. Effects were more pronounced in women than men.

CONCLUSIONS

This work presents a novel finding: evidence that the birth cohorts of the post-World War II Baby Boom appeared to have uniquely low cohort effects on abdominal obesity. The growing prosperity of the post-World War II US may have exposed the baby-boom generation to lower levels of psychosocial and socioeconomic stress than the previous or subsequent generations. By identifying factors associated with the Baby Boomers' low cohort-specific sensitivity to the obesogenic environment, the obesity prevention community can identify early-life factors that can protect future generations from excess weight gain.

'TXT2BFiT' a mobile phone-based healthy lifestyle program for preventing unhealthy weight gain in young adults: study protocol for a randomized controlled trial

BACKGROUND

Despite international efforts to arrest increasing rates of overweight and obesity, many population strategies have neglected young adults as a target group. Young adults are at high risk for unhealthy weight gain which tends to persist throughout adulthood with associated chronic disease health risks.

METHODS/DESIGN

TXT2BFiT is a nine month two-arm parallel-group randomized controlled trial aimed at improving weight management and weight-related dietary and physical activity behaviors among young adults. Participants are recruited via general practice (primary medical care) clinics in Sydney, New South Wales, Australia. All participants receive a mailed resource outlining national physical activity and dietary guidelines and access to the study website. Additional resources accessible to the intervention arm via the study website include Smartphone mobile applications, printable handouts, an interactive healthy weight tracker chart, and a community blog. The study consists of two phases: (1) Intensive phase (weeks 1 to 12): the control arm receives four short message service (SMS) text messages; the intervention arm receives eight SMS messages/week tailored to their baseline stage-of-change, one Email/week, and personalized coaching calls during weeks 0, 2, 5, 8, and 11; and (2) Maintenance phase (weeks 14 to 36): the intervention arm receives one SMS message/month, one Email/month and booster coaching calls during months 5 and 8. A sample of N = 354 (177 per arm) is required to detect differences in primary outcomes: body weight (kg) and body mass index (kg/m2), and secondary outcomes: physical activity, sitting time, intake of specific foods, beverages and nutrients, stage-of-change, self-efficacy and participant well-being, at three and nine months. Program reach, costs, implementation and participant engagement will also be assessed.

DISCUSSION

This mobile phone based program addresses an important gap in obesity prevention efforts to date. The method of intervention delivery is via platforms that are highly accessible and appropriate for this population group. If effective, further translational research will be required to assess how this program might operate in the broader community.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12612000924853.

Changes in BMI and waist circumference in Scottish adults: use of repeated cross-sectional surveys to explore multiple age groups and birth-cohorts

OBJECTIVE

To document changes in body mass index (BMI) and waist circumference (WC) over a 10-year period 1998-2008, in representative surveys of adults.

SUBJECTS

Adults aged 18-72 in the Scottish Health Surveys conducted in 1998, 2003 and 2008 were divided, separately for men and women, into eleven 5-year age bands. 'Synthetic birth-cohorts' were created by dividing participants into thirteen 5-years-of-birth bands (n=20 423). Weight, height and WC were objectively measured by trained observers.

RESULTS

SUBJECTS with data available on BMI/WC were 7743/6894 in 1998, 5838/4437 in 2003 and 4688/925 in 2008 with approximately equal gender distributions. Mean BMI and waist were both greater in successive surveys in both men and women. At most specific ages, people were consistently heavier in 2008 than in 1998 by about 1-1.5 BMI units, and WCs were greater by about 2-6 cm in men and 5-7 cm in women. Greater increases were seen at younger ages between 1998 and 2003 than between 2003 and 2008, however increases continued at older ages, particularly in waist. All birth-cohorts observed over the 10 years 1998-2008 showed increases in both BMI and waist, most marked in the younger groups. The 10-year increases in waist within birth-cohorts (mean 7.4 cm (8.1%) in men and 8.6 cm (10.9%) in women) were more striking than in BMI (mean 1.8 kg m(-2) (6.6%) in men and 1.5 kg m(-2) (6.4%) in women) were particularly steep in older women.

CONCLUSION

People were heavier and fatter in 2003 than those of the same age in 1998, with less marked increases in WC between 2003 and 2008 than between 1998 and 2003. There were proportionally greater increases in WC than in BMI, especially in older women. This suggests a disproportionate increase in body fat, compared with muscle, particularly among older women.

Development of smartphone applications for nutrition and physical activity behavior change

Background

Young adults (aged 18 to 35) are a population group at high risk for weight gain, yet we know little about how to intervene in this group. Easy access to treatment and support with self-monitoring of their behaviors may be important. Smartphones are gaining in popularity with this population group and software applications (“apps”) used on these mobile devices are a novel technology that can be used to deliver brief health behavior change interventions directly to individuals en masse, with potentially favorable cost-utility. However, existing apps for modifying nutrition or physical activity behaviors may not always reflect best practice guidelines for weight management.

Objective

This paper describes the process of developing four apps aimed at modifying key lifestyle behaviors associated with weight gain during young adulthood, including physical activity, and consumption of take-out foods (fast food), fruit and vegetables, and sugar-sweetened drinks.

Methods

The development process involved: (1) deciding on the behavior change strategies, relevant guidelines, graphic design, and potential data collection; (2) selecting the platform (Web-based versus native); (3) creating the design, which required decisions about the user interface, architecture of the relational database, and programming code; and (4) testing the prototype versions with the target audience (young adults aged 18 to 35).

Results

The four apps took 18 months to develop, involving the fields of marketing, nutrition and dietetics, physical activity, and information technology. Ten subjects provided qualitative feedback about using the apps. The slow running speed of the apps (due to a reliance on an active Internet connection) was the primary issue identified by this group, as well as the requirement to log in to the apps.

Conclusions

Smartphone apps may be an innovative medium for delivering individual health behavior change intervention en masse, but researchers must give consideration to the target population, available technologies, existing commercial apps, and the possibility that their use will be irregular and short-lived.

Lifestyle intervention for preventing weight gain in young adults: a systematic review and meta-analysis of RCTs

Younger generations of Australians are gaining weight faster than their parents. Associated health consequences are likely to ensue unless weight gains are prevented; however, it is unclear how to effectively intervene in this population. Electronic databases for health sciences were searched from April to the end of August 2011. Nine studies were included in the review, eight in the meta-analysis, from 771 abstracts reviewed for eligibility criteria: randomized controlled trials of lifestyle interventions, published in English (1980 onward), aimed at preventing weight gain among healthy subjects 18-35 years. Mean body weight change was the primary outcome. The combined weighted mean change in intervention participants was -0.87 kg (95% CI -1.56, -0.18) and in control participants 0.86 kg (95% CI 0.14, 1.57). Post hoc meta-regression analyses revealed evidence-based interventions of 4 months or longer duration were significantly associated with greater weight loss (-1.62 [95% CI -3.21, -0.04], P = 0.045). The small number, short duration and large heterogeneity of trials means the effectiveness of lifestyle intervention for preventing young adult weight gain remains unclear. Future trials conducted over longer periods with larger samples are urgently required to develop effective programmes that will protect against weight gains in future generations.

Obesity and overweight prevalence and its association with undiagnosed hypertension in Shanghai population, China: a cross-sectional population-based survey

The aim of this study was to determine the prevalence of overweight and obese subjects in the Shanghai population of China and its association with undiagnosed hypertension, by taking age, gender and place of residence (urban or suburban) into account. A cross-sectional population-based survey was conducted in 2007. The sample included 13,359 participants aged 15-69 years.Weight, height, and blood pressure were recorded, and information about gender, age and place of residence was obtained. Overweight and obesity prevalence were calculated by the body mass index (BMI) definition recommended by Working Group on Obesity in China (normal weight, 18.5-23.9 kg/m(2); overweight, 24-27.9 kg/m(2); obesity, ≥ 28 kg/m(2)). Undiagnosed hypertension was defined by China criteria in accord with that of WHO-ISH (subjects with systolic pressure ≥ 140 mmHg, and/or diastolic pressure ≥ 90 mmHg). Multiple logistic regression analyses were used to assess the association of overweight or obesity with undiagnosed hypertension by adjusting for age, gender and place of residence. The overall overweight, obesity, and undiagnosed hypertension prevalence were 27.6% (95% CI: 26.8-28.4), 6.6% (95% CI: 6.2-7.0), and 15.5% (95% CI: 14.9-16.1), respectively. Compared to normal weight subjects, the odds ratios (OR) for subjects who were overweight and had hypertension was 2.33 (95% CI: 2.10-2.59); that for obesity and hypertension was 4.27 (95% CI: 3.66-4.99). These data suggest that overweight and obesity prevalence and their association with undiagnosed hypertension are high in our study population.

Future predictions of body mass index and overweight prevalence in Australia, 2005-2025

To predict current and future body mass index (BMI) and prevalence of overweight and obesity in Australian children and adults based on sex, age and year of birth (cohort). These predictions are needed for population health planning and evaluation. Data were drawn from 11 cross-sectional national or state population surveys conducted in Australia between 1969 and 2004. These included representative population samples of children (n= 27,635) and adults (n= 43,447) aged 5 years or older with measured height and weight data. Multiple linear regression analyses of measured log-transformed BMI data were conducted to determine the independent effects of age and year of birth (cohort) on ln(BMI) for males and females, respectively. Regression coefficients for cohort obtained from these analyses were applied to the National Nutrition Survey 1995 data set to predict mean BMI and prevalence of overweight (BMI 25-29.99 kg/m(2)) and obesity (BMI ≥ 30 kg/m(2)) in 2005, 2015 and 2025. Based on past trends, BMI is predicted to continue to increase for both males and females and across the age span. This would result in increases in the prevalence of overweight and obesity of between 0.4 and 0.8% per year, such that by 2025 around one-third of 5-19 year olds will be overweight or obese as will 83% of males and 75% of females aged 20 years and over. The increases in prevalence and mean BMI predicted in this study will have significant impacts on disease burden, healthcare costs and need for prevention and treatment programmes.

Birth cohort differences in anthropometric measures in the older elderly: the Bambuí cohort study of aging (1997 and 2008)

The aim of this study was to evaluate the effect of birth cohort on nutritional status among older elderly (71-81 years old) from the Bambuí Cohort Study of Aging, conducted in Brazil in 1997 and 2008. We compared the two birth cohorts - 1916-1926 (older cohort) and 1927-1937 (recent cohort) - considering body mass index (BMI = weight/height²), waist circumference (WC) and prevalence of overweight (BMI ³ 27kg/m²). BMI (β = 0.09, 95%CI: 0.04, 0.15) and prevalence of overweight (PR = 1.02; 95%CI: 1.01; 1.03) were higher in the recent cohort than the earlier cohort, regardless of sex and schooling. No difference was observed in WC. Stratified by sex, similar overall trends were observed for men, and WC was higher in the recent cohort. Among women there was no difference in BMI and overweight, but WC was lower in the recent cohort. The cohort effect was greater among older men and, in the near future, may result in greater prevalence of overweight in this group.

Mismatch between perceived and objectively assessed neighborhood walkability attributes: prospective relationships with walking and weight gain

We examined prospectively whether persons who perceive their objectively measured high walkable environment as low walkable decrease their walking more and gain more weight than those with matched perceptions. Walkability was measured objectively using GIS. Corresponding perceptions were collected using the Neighborhood Environment Walkability Scale from 1027 urban Australian adults. Objective and perceived measures were dichotomized and categories of match and mismatch were created. Overall, walking levels decreased and BMI increased significantly over the four year follow-up period. Those who perceived high walkability, dwelling density or land use mix as low decreased their walking for transport significantly more than those with matched perceptions. Those who perceived high walkability, land use mix or retail density as low increased their BMI significantly more than those with concordant perceptions. These prospective findings corroborate recommendations from previous cross-sectional studies. Interventions to improve negative perceptions of walkability among those living in high walkable areas may be a relevant public health intervention to increase physical activity and support weight maintenance.

The levelling off of the obesity epidemic since the year 1999--a review of evidence and perspectives

The purpose was to investigate a possible levelling off in the obesity epidemic, by systematically reviewing literature and web-based sources. Eligible studies and data sources were required to have at least two measures of obesity prevalence since 1999. A literature and Internet search resulted in 52 studies from 25 different countries. The findings supported an overall levelling off of the epidemic in children and adolescents from Australia, Europe, Japan and the USA. In adults, stability was found in the USA, while increases were still observed in some European and Asian countries. Some evidence for heterogeneity in the obesity trends across socioeconomic status (SES) groups was found. The levelling off was less evident in the lower-SES groups. No obvious differences between genders were identified. We discussed potential explanations for a levelling off and the utility of investigating obesity trends to identify the driving forces behind the epidemic. It is important to emphasize that the levelling off is not tantamount to calling off the epidemic. Additionally, it is worthwhile to keep in mind that previous stable phases have been followed by further increases in the prevalence of obesity. Therefore, research into the causes, prevention and treatment of obesity should remain a priority.

[Diabetes and chronic kidney disease: lessons from renal epidemiology]

In industrialized countries, renal epidemiology is faced with the growing epidemic of diabetes as cause of renal involvement or as an associated condition. In France, recent studies estimate that 400,000+ diabetics have a glomerular filtration rate lower than 60 mL/min/1.73 m², and that 7000+ are prevalent in dialysis. The vast majority has type 2 diabetes. In type 1 diabetes, renal prognosis improved over the last decade due to available aggressive glycemic control and treatment with renin-angiotensin system inhibitors. Diabetes has a negative impact on survival in end-stage renal disease, particularly for type 1 diabetes patients and for women with diabetes. In type 2 diabetes, improvement in early access to renal transplant could lead to improvement in outcomes, whereas they are usually contra-indicated for transplant because rapid decline in cardiovascular status on dialysis. All these epidemiological data help us to implement preventing measures and further researches in order to improve diabetes patient prognosis.

Studies using routine data versus specific data collection: What can we learn about the epidemiology of eclampsia and the impact of changes in management of gestational hypertensive disorders?

Evidence-based changes in practice, services and policy may impact on the spectrum of pregnancy hypertensive disorders at many levels. Demonstration of clinical benefit relies on assessment of changes in disease incidence or complications. Two main alternative observational methodologies may be used to investigate changes in disease incidence; the first using routinely collected data and the second with specially designed prospective data collection. Routinely collected data have been shown to have limitations; the introduction of specific prospective data collection systems, such as the UK Obstetric Surveillance System, allow for an increased robustness and range of disease incidence and outcome studies, and thus enhance our ability to investigate the impact of changes in practice. The comparison of recent national studies using these systems shows that the incidence of eclampsia has declined in the UK, but that the incidence of eclampsia is higher in the Netherlands and Scandinavia. The decrease in the UK is clearly due to a fall in the number of women with diagnosed pre-eclampsia who go on to have an eclamptic fit; figures from the Netherlands and Scandinavia suggest that eclamptic fits in the group with prior diagnosed pre-eclampsia are less effectively prevented and this may be the reason for the observed higher incidence of eclampsia. This information may help to further inform management and preventive strategies, and illustrates the additional benefits of international comparisons of severe maternal morbidities.

Evolution of obesity prevalence in France: an age-period-cohort analysis

BACKGROUND

A rapid increase in the prevalence of obesity has been reported in France since 1990. We investigated the impact of birth cohort on the changes in obesity prevalence after taking into account age and survey period.

METHODS

We analyzed data from 4 national surveys in 1997, 2000, 2003, and 2006. For each survey, self-reported data on weight and height were recorded on mailed questionnaires sent to a sample of 20,000 households, representative of the French population. Obesity was defined according to World Health Organization criteria as body mass index >or=30 kg/m. We modeled the prevalence of obesity using logistic regression with age, cohort, and period as explanatory variables. As these variables are linearly dependent, only nonlinear effects can be estimated uniquely and interpreted, after including specific chosen constraints in the models.

RESULTS

There was a progressive increase in the prevalence of obesity between 1997 and 2006, attributable either to a period effect or to a cohort effect. There was a substantial departure from a linear trend for the cohort effect only, which seemed to be stronger in women: there was an acceleration in the prevalence of obesity with birth cohort for individuals born after the mid-1960s, in both sexes.

CONCLUSIONS

Our results are consistent with previous studies in other countries. Compared with older generations, men and women born in the late 1960s may have been subject to early exposures that increased their lifelong susceptibility to obesity.

What is a cohort effect? Comparison of three statistical methods for modeling cohort effects in obesity prevalence in the United States, 1971-2006

Analysts often use different conceptual definitions of a cohort effect, and therefore different statistical methods, which lead to differing empirical results. A definition often used in sociology assumes that cohorts have unique characteristics confounded by age and period effects, whereas epidemiologists often conceive that period and age effects interact to produce cohort effects. The present study aims to illustrate these differences by estimating age, period, and cohort (APC) effects on obesity prevalence in the U.S. from 1971 to 2006 using both conceptual approaches. Data were drawn from seven cross-sectional waves of the National Health and Nutrition Examination Survey. Obesity was defined as BMI >or=30 for adults and >or=95th percentile for children under the age of 20. APC effects were estimated using the classic constraint-based method (first-order effects estimated and interpreted), the Holford method (first-order effects estimated but second-order effects interpreted), and median polish method (second-order effects are estimated and interpreted). Results indicated that all methods report significant age and period effects, with lower obesity prevalence in early life as well as increasing prevalence in successive surveys. Positive cohort effects for more recently born cohorts emerged based on the constraint-based model; when cohort effects were considered second-order estimates, no significant effects emerged. First-order estimates of age-period-cohort effects are often criticized because of their reliance on arbitrary constraints, but may be conceptually meaningful for sociological research questions. Second-order estimates are statistically estimable and produce conceptually meaningful results for epidemiological research questions. Age-period-cohort analysts should explicitly state the definition of a cohort effect under consideration. Our analyses suggest that the prevalence of obesity in the U.S. in the latter part of the 20th century rose across all birth cohorts, in the manner expected based on estimated age and period effects. As such, the absence or presence of cohort effects depends on the conceptual definition and therefore statistical method used.

Trends in postpartum hemorrhage in high resource countries: a review and recommendations from the International Postpartum Hemorrhage Collaborative Group

BACKGROUND

Postpartum hemorrhage (PPH) is a major cause of maternal mortality and morbidity worldwide. Several recent publications have noted an increasing trend in incidence over time. The international PPH collaboration was convened to explore the observed trends and to set out actions to address the factors identified.

METHODS

We reviewed available data sources on the incidence of PPH over time in Australia, Belgium, Canada, France, the United Kingdom and the USA. Where information was available, the incidence of PPH was stratified by cause.

RESULTS

We observed an increasing trend in PPH, using heterogeneous definitions, in Australia, Canada, the UK and the USA. The observed increase in PPH in Australia, Canada and the USA was limited solely to immediate/atonic PPH. We noted increasing rates of severe adverse outcomes due to hemorrhage in Australia, Canada, the UK and the USA.

CONCLUSION

Key Recommendations 1. Future revisions of the International Classification of Diseases should include separate codes for atonic PPH and PPH immediately following childbirth that is due to other causes. Also, additional codes are required for placenta accreta/percreta/increta. 2. Definitions of PPH should be unified; further research is required to investigate how definitions are applied in practice to the coding of data. 3. Additional improvement in the collection of data concerning PPH is required, specifically including a measure of severity. 4. Further research is required to determine whether an increased rate of reported PPH is also observed in other countries, and to further investigate potential risk factors including increased duration of labor, obesity and changes in second and third stage management practice. 5. Training should be provided to all staff involved in maternity care concerning assessment of blood loss and the monitoring of women after childbirth. This is key to reducing the severity of PPH and preventing any adverse outcomes. 6. Clinicians should be more vigilant given the possibility that the frequency and severity of PPH has in fact increased. This applies particularly to small hospitals with relatively few deliveries where management protocols may not be defined adequately and drugs or equipment may not be on hand to deal with unexpected severe PPH.

Do birth cohorts matter? Age-period-cohort analyses of the obesity epidemic in the United States

Many studies have cited the importance of secular changes or "period effects" as causes of the U.S. obesity epidemic. Unfortunately, relatively little attention has been devoted to the possible influence of cohort-related mechanisms. To address this current gap in the scientific literature, this investigation utilized the responses from 1.7 million participants in the 1976-2002 National Health Interview Surveys to determine how birth cohorts may have contributed to the rapid increase in the prevalence of obesity. Results from hierarchical age-period-cohort (HAPC) models confirmed that period effects are principally responsible for the U.S. obesity epidemic. However, HAPC models also demonstrated that birth cohort membership is influential. Independent of age and period effects, the predicted probability of obesity at age 25 increased by 30% for cohorts born between 1955 and 1975. Our results also showed that age, period and cohort effects varied by race/gender and educational attainment. For instance, increases in the predicted probabilities of obesity were particularly sharp for recent cohorts of Black females. Our investigation successfully demonstrated that both secular change and birth cohort membership have independently contributed to elevated odds of obesity among recent generations of Americans, suggesting that cohort-specific strategies may be needed to combat disconcertingly high rates of obesity in the U.S.

Determinants and patterns of soft drink consumption in young adults: a qualitative analysis

Objective

To explore knowledge, attitudes and behaviours regarding caloric soft drinks in a group of young adults attending university and to identify opportunities for a health promotion intervention aimed at reducing consumption.

Design

In-depth, semi-structured focus groups segmented by gender.

Setting

Sydney, Australia.

Subjects

Undergraduate University of Sydney students aged 18–30 years (n 35).

Results

Social and environmental cues, intrinsic qualities of beverages and personal health beliefs were identified as important influences on consumption. Social cues included settings in which alcohol is usually consumed, socialising with friends, and family influences. Environmental cues included purchasing of fast foods, and ready availability, preferential pricing and promotion of caloric beverages. Reinforcing intrinsic qualities of caloric soft drinks included taste, sugar and caffeine content, and their association with treats and rewards. Major gender differences as well as variations in individual readiness for behaviour change were observed. Raising awareness of the sugar content of various beverages and the potential health impacts associated with their consumption was considered important.

Conclusions

The findings provide new insights with important implications for policy and practice, and suggest that there is considerable scope for promoting awareness in this group. Carefully designed social marketing campaigns highlighting the health issues and addressing social and environmental cues relating to caloric soft drink consumption are required. There is a need for gender-differentiated intervention programmes which are both informational and appealing to young adults. Further research is warranted, particularly to investigate beverage consumption relating to fast-food meal deals and young adults’ consumption patterns in more depth.

Marital status, marital transitions, and body weight

We consider how marital status and marital transitions, important features of the social environment, influence weight change over time, and how these effects vary by age, race, and gender. Growth curve analysis of a four-wave national survey suggests that marital transitions are more important than marital status in predicting change in body weight, and that marital dissolution is more important than marital formation in affecting weight. Widowhood effects on weight loss are a particular concern for population health trends, especially among African Americans.

Obesity and overweight prevalences in rural and urban populations in East Spain and its association with undiagnosed hypertension and Diabetes Mellitus: a cross-sectional population-based survey

Background

An increase in the number of overweight and obese subjects in the general population has been observed.

The aim of this study was to determine the prevalence of overweight and obese subjects in the general population and its association with undiagnosed pathologies, such as diabetes mellitus [DM] and hypertension [HT], by taking age, gender and place of residence [rural or urban] into account.

Findings

A cross-sectional population-based survey was conducted in Castellón, East Spain in 2005–2006. The sample included 2,062 participants aged 18–94 years. Weight, height, blood pressure and glycaemia values were recorded, and information about gender, age and place of residence was obtained. Overweight, obesity, and undiagnosed HT and DM prevalences were calculated. Multiple regression analyses were done to assess the association of overweight/obesity with undiagnosed HT and DM by adjusting for age, gender and place of residence.

The overall overweight, obesity, and undiagnosed HT and DM prevalences were 39.9% [95% CI:37.3–42.0], 25.9% [95% CI:24.0–27.9], 9.0% [95% CI:7.8–10.4] and 12.6% [95% CI:11.2–14.1], respectively. We identified various independent risk factors; those relating to overweight were increasing age, male gender and rural residential area, while that relating to obesity was increasing age. Compared to normal weight adults, the Relative Prevalence Ratio (RPR) for subjects who were overweight and had HT was 2.00 [95% CI:1.21–3.32]; that for obesity and HT was 1.91 [95% CI:1.48–2.46], and it was 1.50 [95% CI:1.25–1.81] for obesity and DM.

Conclusion

Overweight and obesity prevalences, and their association with undiagnosed DM and HT, are high in our study population.

Changes in body mass index by birth cohort in Japanese adults: results from the National Nutrition Survey of Japan 1956-2005

Background The National Nutrition Survey, Japan (NNS-J) provides annual anthropometric information for a whole nation over 50 years. Based on this survey, the mean body mass index (BMI) of Japanese men and elderly women has increased in recent decades, but that of young women has decreased. We examined the effect of birth cohort on this phenomenon.

Methods We analysed data from the NNS-J for subjects aged 20–69 years. BMI during 1956–2005 and the prevalence of overweight and obesity (BMI ≥ 25 kg/m²) during 1976–2005 were estimated.

Results The BMI increased with age in every birth cohort, with similar increments, and did not peak until 60–69 years of age. However, with cross-sectional age, the BMI usually peaked before 60–69 years of age. The differences among cohorts already existed at 20–29 years of age, and slightly increased in men between 20–29 and 30–39 years of age. The BMI in all male age groups increased from the 1891–1900 through 1971–80 cohorts. However, in women, the figure increased until the 1931–40 cohorts, but later decreased. Changes in prevalence were generally consistent with changes in BMI. The recent increase (decrease in young women) in the mean BMI is attributable to birth cohort, indicating that thinner (fatter) and less recent birth cohorts have been replaced by fatter (thinner) ones.

Conclusions A cohort effect was quantitatively demonstrated based on a repeated annual survey. In Japan, the differences in BMI among cohorts were already established by young adulthood.