Beyond the Economic Gaze: Childbearing During and After Recessions in the Nordic Countries

During the 2010s, fertility rates fell across the Nordic region. The onset of these declines seems linked to the Great Recession of 2008-2009, but their continuation cannot easily be linked to subsequent economic change. The 1990s, too, brought episodes of economic crises to the Nordic region that were followed by different degrees of fertility decline. In this study, we provide an empirical overview of parity-, age- and education-specific fertility developments in the five Nordic countries in the wake of the economic recessions in 2008 and the early 1990s, respectively. We demonstrate a high degree of heterogeneity in fertility developments across countries after 1990, whereas after 2008, the trends are much more similar across the five countries. Likewise, the educational differences in birth hazards that characterized the developments after 1990 were much smaller in the initial years after 2008-2009. This reversal from heterogeneity to homogeneity in the fertility response to recessions calls for an expansion of theories on the cyclicality of fertility in relation to uncertainty and economic and social change. In our discussion, we consider the role of a set of factors that also incorporates the state, crisis management, and perceptions of economic and welfare uncertainty.

Lifestyle Habits and Mental Health in Light of the Two COVID-19 Pandemic Waves in Sweden, 2020

The COVID-19 pandemic has become a public health emergency of international concern, which may have affected lifestyle habits and mental health. Based on national health profile assessments, this study investigated perceived changes of lifestyle habits in response to the COVID-19 pandemic and associations between perceived lifestyle changes and mental health in Swedish working adults. Among 5599 individuals (50% women, 46.3 years), the majority reported no change (sitting 77%, daily physical activity 71%, exercise 69%, diet 87%, alcohol 90%, and smoking 97%) due to the pandemic. Changes were more pronounced during the first wave (April–June) compared to the second (October–December). Women, individuals <60 years, those with a university degree, white-collar workers, and those with unhealthy lifestyle habits at baseline had higher odds of changing lifestyle habits compared to their counterparts. Negative changes in lifestyle habits and more time in a mentally passive state sitting at home were associated with higher odds of mental ill-health (including health anxiety regarding one’s own and relatives’ health, generalized anxiety and depression symptoms, and concerns regarding employment and economy). The results emphasize the need to support healthy lifestyle habits to strengthen the resilience in vulnerable groups of individuals to future viral pandemics and prevent health inequalities in society.

Anti-apoptotic effect of adipose tissue-derived stromal vascular fraction in denervated rat muscle

BACKGROUND

Recovery of muscle function after peripheral nerve injury is often poor, and this can be attributed to muscle fiber atrophy and cell death. In the current study, we have investigated the effects of stromal vascular fraction (SVF) on muscle cell apoptosis and its potential to preserve muscle tissue following denervation.

METHODS

Rat gastrocnemius muscle was denervated by sciatic nerve transection. At 2 and 4 weeks after injury, muscles were examined histologically and apoptosis was measured using TUNEL assay and PCR array for a range of apoptotic genes. Additionally, an in vitro TNF-α apoptosis model was established using SVF cells co-cultured indirectly with primary rat myoblasts. Annexin V and TUNEL were used together with Western blotting to investigate the signaling pathways.

RESULTS

Denervated muscles showed significantly higher TUNEL reactivity at 2 and 4 weeks following nerve injury, and an increased expression of caspase family genes, mitochondria-related apoptotic genes, and tumor necrosis factor family genes. In cultured rat primary myoblasts, Annexin V labeling was significantly increased at 12 h after TNF-α treatment, and this was followed by a significant increase in TUNEL reactivity at 48 h. Western blotting showed that caspase-7 was activated/cleaved as well as the downstream substrate, poly (ADP-ribose) polymerase (PARP). Co-culture of myoblasts with SVF significantly reduced all these measures of apoptosis. Bax and Bcl-2 levels were not changed suggesting that the TNF-α-induced apoptosis occurred via mitochondria-independent pathways. The protective effect of SVF was also shown in vivo; injections of SVF cells into denervated muscle significantly improved the mean fiber area and diameter, as well as reduced the levels of TUNEL reactivity.

CONCLUSIONS

This study provides new insights into how adipose tissue-derived cells might provide therapeutic benefits by preserving muscle tissue.

Scaling VO2max to body size differences to evaluate associations to CVD incidence and all-cause mortality risk

Objective

To evaluate and compare ratio and allometric scaling models of maximal oxygen consumption (VO₂max) for different body size measurements in relation to cardiovascular disease (CVD) incidence and all-cause mortality.

Methods

316 116 individuals participating in occupational health screenings, initially free from CVD, were included. VO₂max was estimated using submaximal cycle test. Height, body mass and waist circumference (WC) were assessed, and eight different scaling models (two evaluated in a restricted sample with WC data) were derived. Participants were followed in national registers for first-time CVD event or all-cause mortality from their health screening to first CVD event, death or 31 December 2015.

Results

Increasing deciles of VO₂max showed lower CVD risk and all-cause mortality for all six models in the full sample (p<0.001) as well as with increasing quintiles in the restricted sample (eight models) (p<0.001). For CVD risk and all-cause mortality, significantly weaker associations with increasing deciles for models 1 (L·min⁻¹) and 5 (mL·min⁻¹·height⁻²) were seen compared with model 2 (mL·min⁻¹·kg⁻¹), (CVD, p<0.00001; p<0.00001: all-cause mortality, p=0.008; p=0.001) and in some subgroups. For CVD, model 6 (mL·min⁻¹·(kg¹·height⁻¹)⁻¹) had a stronger association compared with model 2 (p<0.00001) and in some subgroups.

In the restricted sample, trends for significantly stronger associations for models including WC compared with model 2 were seen in women for both CVD and all-cause mortality, and those under 50 for CVD.

Conclusion

In association to CVD and all-cause mortality, only small differences were found between ratio scaling and allometric scaling models where body dimensions were added, with some stronger associations when adding WC in the models.

Physical Activity, Sedentary Behavior, and Cardiorespiratory Fitness in Hazardous and Non-Hazardous Alcohol Consumers

Purpose:

To describe physical activity habits, sedentary behavior, and cardiorespiratory fitness levels among alcohol abstainers, hazardous and non-hazardous drinkers.

Design:

Cross-sectional study with data collected between 2017-19.

Setting:

Sweden.

Subjects:

Adults aged 18-65 years (n = 47,559; 59.4% male).

Measures:

During a routine health assessment, participants answered validated single-item questions regarding: habitual physical activity, structured exercise, and the percentage of time spent sedentary during leisure-time (past 30 days), and completed a 6-minute cycle ergometer test (V02max) to determine cardiorespiratory fitness (CRF). Participants were categorized as alcohol abstainers, non-hazardous drinkers or hazardous drinkers (low/high) based on the Alcohol Use Disorders Identification Test (AUDIT-C) cut-points for men and women.

Analysis:

Logistic regression models stratified by sex and age.

Results:

Compared to non-hazardous drinkers, the heaviest drinkers were less physically active (males: OR = 1.38, CI = 1.13-1.67, p = .001; females: OR = 1.41, CI = 1.01-1.97, p = .040) and more sedentary during leisure time (males: OR = 1.94, CI = 1.62-2.32, p = .000; females: OR = 1.62, CI = 1.21-2.16, p = .001). Apart from young females, the heaviest drinkers also did less structured exercise than non-hazardous drinkers (males: OR = 1.22, CI = 1.15-1.51, p = .000; females: OR = 1.43, CI = 1.15-1.78, p = .001). The strongest associations were seen among adults aged 40-65 years (shown here). High-hazardous drinking was associated with low CRF among older males only (OR = 1.19, CI = 1.00-1.41).

Conclusion:

Middle-aged adults with AUDIT-C scores of ≥6 (women) and ≥7 (men) were less physically active and more sedentary during leisure time and may be appropriate targets for physical activity interventions.

Two Decades of Same-Sex Marriage in Sweden: A Demographic Account of Developments in Marriage, Childbearing, and Divorce

In this study, we provide demographic insight into the still relatively new family form of same-sex marriage. We focus on period trends in same-sex marriage formation and divorce during 1995–2012 in Sweden and the role of childbearing in same-sex unions. The period begins with the introduction of registered partnership for same-sex couples and also covers the introduction of formal same-sex marriage in 2009. We use register data for the complete population of Sweden to contrast patterns in male and female same-sex marriage formation and divorce. We show that female same-sex union formation increased rapidly over the period, while trends for male same-sex unions increased less. The introduction of same-sex marriage legislation in 2009 appears to have had little effect on the pace of formation of same-sex unions. In contrast, legal changes supporting parental rights in same-sex unions may have fueled the formation of female same-sex marriages as well as parenthood in such unions. Further, we show that divorce risks in the marital unions of two women are much higher than in other types of marriages. We find some convergence of divorce risks across union types at the end of our study period: male same-sex unions have the same divorce risk levels as opposite-sex marriages, and the elevated risks of divorce in female same-sex unions appear to have stabilized at somewhat lower levels than those observed in the late 1990s.

Lifestyle-associated health risk indicators across a wide range of occupational groups: a cross-sectional analysis in 72,855 workers

Background

Identify and compare health risk indicators for common chronic diseases between different occupational groups.

Methods

A total of 72,855 participants (41% women) participating in an occupational health service screening in 2014–2019 were included. Occupation was defined by the Swedish Standard Classification of Occupation, and divided into nine major and additionally eight sub-major groups. These were analysed separately, as white- and blue-collar occupations and as low- and high-skilled occupations. Seven health risk indicators were self-reported: exercise, physical work situation, sitting at work and leisure, smoking, diet, and perceived health, whereas cardiorespiratory fitness, BMI and blood pressure were measured. These were further dichotomized (yes/no) and as clustering of risk indicators (≥3 vs. <3).

Results

The greatest variation in OR across sub-major and major occupational groups were seen for daily smoking (OR = 0.68 to OR = 5.12), physically demanding work (OR = 0.55 to OR = 45.74) and high sitting at work (OR = 0.04 to OR = 1.86). For clustering of health risk indicators, blue-collar workers had significantly higher clustering of health risks (OR: 1.80; 95% CI 1.71–1.90) compared to white-collar workers (reference). Compared to high-skilled white-collar workers, low-skilled white-collar workers had similar OR (2.00; 1.88–2.13) as high-skilled blue-collar workers (1.98; 1.86–2.12), with low-skilled blue-collar workers having the highest clustered risk (2.32; 2.17–2.48).

Conclusion

There were large differences in health risk indicators across occupational groups, mainly between high-skilled white-collar occupations and the other occupations, with important variations also between major and sub-major occupational groups. Future health interventions should target the occupational groups identified with the highest risk for effective disease prevention.

Residential context and COVID-19 mortality among adults aged 70 years and older in Stockholm: a population-based, observational study using individual-level data

BACKGROUND

Housing characteristics and neighbourhood context are considered risk factors for COVID-19 mortality among older adults. The aim of this study was to investigate how individual-level housing and neighbourhood characteristics are associated with COVID-19 mortality in older adults.

METHODS

For this population-based, observational study, we used data from the cause-of-death register held by the Swedish National Board of Health and Welfare to identify recorded COVID-19 mortality and mortality from other causes among individuals (aged ≥70 years) in Stockholm county, Sweden, between March 12 and May 8, 2020. This information was linked to population-register data from December, 2019, including socioeconomic, demographic, and residential characteristics. We ran Cox proportional hazards regressions for the risk of dying from COVID-19 and from all other causes. The independent variables were area (m2) per individual in the household, the age structure of the household, type of housing, confirmed cases of COVID-19 in the borough, and neighbourhood population density. All models were adjusted for individual age, sex, country of birth, income, and education.

FINDINGS

Of 279 961 individuals identified to be aged 70 years or older on March 12, 2020, and residing in Stockholm in December, 2019, 274 712 met the eligibility criteria and were included in the study population. Between March 12 and May 8, 2020, 3386 deaths occurred, of which 1301 were reported as COVID-19 deaths. In fully adjusted models, household and neighbourhood characteristics were independently associated with COVID-19 mortality among older adults. Compared with living in a household with individuals aged 66 years or older, living with someone of working age (<66 years) was associated with increased COVID-19 mortality (hazard ratio 1·6; 95% CI 1·3-2·0). Living in a care home was associated with an increased risk of COVID-19 mortality (4·1; 3·5-4·9) compared with living in independent housing. Living in neighbourhoods with the highest population density (≥5000 individuals per km2) was associated with higher COVID-19 mortality (1·7; 1·1-2·4) compared with living in the least densely populated neighbourhoods (0 to <150 individuals per km2).

INTERPRETATION

Close exposure to working-age household members and neighbours is associated with increased COVID-19 mortality among older adults. Similarly, living in a care home is associated with increased mortality, potentially through exposure to visitors and care workers, but also due to poor underlying health among care-home residents. These factors should be considered when developing strategies to protect this group.

FUNDING

Swedish Research Council for Health, Working Life and Welfare (FORTE), Swedish Foundation for Humanities and Social Sciences.

Transcriptomes from German shepherd dogs reveal differences in immune activity between atopic dermatitis affected and control skin

Canine atopic dermatitis (CAD) is an inflammatory and pruritic allergic skin disease with both genetic and environmental risk factors described. We performed mRNA sequencing of non-lesional axillary skin biopsies from nine German shepherd dogs. Obtained RNA sequences were mapped to the dog genome (CanFam3.1) and a high-quality skin transcriptome was generated with 23,510 expressed gene transcripts. Differentially expressed genes (DEGs) were defined by comparing three controls to five treated CAD cases. Using a leave-one-out analysis, we identified seven DEGs: five known to encode proteins with functions related to an activated immune system (CD209, CLEC4G, LOC102156842 (lipopolysaccharide-binding protein-like), LOC480601 (regakine-1-like), LOC479668 (haptoglobin-like)), one (OBP) encoding an odorant-binding protein potentially connected to rhinitis, and the last (LOC607095) encoding a novel long non-coding RNA. Furthermore, high mRNA expression of inflammatory genes was found in axillary skin from an untreated mild CAD case compared with healthy skin. In conclusion, we define genes with different expression patterns in CAD case skin helping us understand post-treatment atopic skin. Further studies in larger sample sets are warranted to confirm and to transfer these results into clinical practice.

Associations of interruptions to leisure-time sedentary behaviour with symptoms of depression and anxiety

Interruptions to time spent sitting can ameliorate detrimental metabolic-health consequences of high volumes of sedentary time, but their potential mental health benefits have not been examined. We used the Swedish Health Profile Assessment database, a general health assessment offered to all employees working for companies or organisations connected to occupational and health services. Cross-sectional analyses examined data from 40,550 employees (60% male, mean age = 42 years), collected in 2017-2019. Participants reported the proportion of time (almost always; 75% of the time; 50% of the time; 25% of the time; and almost never) usually spent in leisure-time sedentary behaviours; and, separately, the frequency (never; rarely; sometimes; often; and very often) of interruptions (every 30 min) to sedentary time. Logistic regression models assessed associations of sedentary time, and the frequency of interruptions to sedentary time, with depression/anxiety symptoms. Fully adjusted models included physical exercise. Compared to those in the lowest sedentary time category, those in the medium and high categories had 1.52 (95% confidence interval (CI) = 1.40-1.66) and 3.11 (95% CI = 2.82-3.42) higher odds of frequent depression/anxiety symptoms, respectively. Compared to those who never/rarely interrupted their sedentary time, those who reported interruptions sometimes, often and very often had 0.72 (95% CI = 0.65-0.80), 0.59 (95% CI = 0.53-0.65), and 0.53 (95% CI = 0.46-0.59) lower odds of depression/anxiety symptoms, respectively. In stratified analyses, more frequent interruptions to sedentary time were associated with lower odds of depression/anxiety symptoms, except among those in the lowest interruptions categories (never/25% of the time). More regularly interrupting sitting during leisure-time may reduce the odds of experiencing symptoms of depression and anxiety.

Prevalence and time trends of overweight, obesity and severe obesity in 447,925 Swedish adults, 1995-2017

Aims: The purpose of this research was to describe the current prevalence and historic trends in overweight, obesity and severe obesity in Sweden. Methods: Data on BMI, age, gender, education and geographic region were obtained in n=447,925 Swedish adults through a nationwide screening test (1995–2017). To account for sampling variations, we quantified prevalence estimates and time trends using standardized values (direct method) to all 18–74-year-old Swedes, using nationwide databases. Rates of overweight (BMI ⩾25 kg/m²), obesity (BMI ⩾30 kg/m²) and severe obesity (BMI ⩾35 kg/m²) were calculated across gender, age, education and geographic categories. Years were grouped into two-year sampling periods (except the first period where we used three years) for increased power. We used multivariable logistic regression to quantify independent associations between age, gender, education and region with obesity development and current prevalence rates. Results: In 2016/17 the unstandardized prevalence of overweight, obesity and severe obesity were 55.1%, 16.6% and 4.2%, respectively. Factors associated with a higher obesity prevalence were male gender, older age, lower education and residing in a rural region (all P<0.001). Between 1995 and 2017 the prevalence of severe obesity increased by 153%, compared to obesity (+86%) and overweight (+23%). While there were similar increases in obesity across gender and age groups, people with low education (vs high) and rural areas (vs urban) had a higher prevalence increase (both P<0.001). Conclusions: Rates of overweight, obesity and severe obesity have increased markedly in Swedish adults since 1995. Priority groups for prevention efforts include individuals with low education and those living in rural areas.

Latent profile analysis patterns of exercise, sitting and fitness in adults - Associations with metabolic risk factors, perceived health, and perceived symptoms

Aim

To identify and describe the characteristics of naturally occurring patterns of exercise, sitting in leisure time and at work and cardiorespiratory fitness, and the association of such profiles with metabolic risk factors, perceived health, and perceived symptoms.

Methods

64,970 participants (42% women, 18–75 years) participating in an occupational health service screening in 2014–2018 were included. Exercise and sitting were self-reported. Cardiorespiratory fitness was estimated using a submaximal cycle test. Latent profile analysis was used to identify profiles. BMI and blood pressure were assessed through physical examination. Perceived back/neck pain, overall stress, global health, and sleeping problems were self-reported.

Results

Six profiles based on exercise, sitting in leisure time and at work and cardiorespiratory fitness were identified and labelled; Profile 1 “Inactive, low fit and average sitting in leisure, with less sitting at work”; Profile 2 “Inactive, low fit and sedentary”; Profile 3 “Active and average fit, with less sitting at work”; Profile 4 “Active, average fit and sedentary in leisure, with a sedentary work” (the most common profile, 35% of the population); Profile 5 “Active and fit, with a sedentary work”; Profile 6 “Active and fit, with less sitting at work”. Some pairwise similarities were found between profiles (1 and 2, 3 and 4, 5 and 6), mainly based on similar levels of exercise, leisure time sitting and fitness, which translated into similar dose-response associations with the outcomes. In general, profile 1 and 2 demonstrated most adverse metabolic and perceived health, profile 4 had a more beneficial health than profile 3, as did profile 6 compared to profile 5.

Conclusions

The present results implies a large variation in exercise, sitting, and fitness when studying naturally occurring patterns, and emphasize the possibility to target exercise, sitting time, and/or fitness in health enhancing promotion intervention and strategies.

Geographical variations in the incidence of oesophageal cancer in Sweden

Background: Geographical variations in the incidence and tumour stage distribution of oesophageal cancer in Sweden are not well characterised.Methods: Using data from the Swedish Cancer Registry over 45 years (1972-2016), we compared the age-standardised incidence rates of oesophageal cancer by histological type across all seven national areas (in five-year periods) and 21 counties (in 15-year periods) in Sweden, and assessed the geographical distribution of tumour stage at diagnosis since 2004.Results: The incidence rate of oesophageal adenocarcinoma increased in all national areas and counties and in both sexes over time, while the rate of oesophageal squamous cell carcinoma decreased from the 1980s onwards. In the latest period (2012- 2016), the incidence rate of adenocarcinoma in men ranged from 3.5/100,000 person-years in West Sweden to 6.2/100,000 person-years in North Middle Sweden. At the county level, the rate of adenocarcinoma in men was lowest in Jämtland (2.7/100,000 person-years) and highest in Gotland (6.2/100 000 person-years) in 2002-2016. The incidence rates of both adenocarcinoma and squamous cell carcinoma in women were below 2/100,000 person-years in all national areas and counties in the latest calendar periods, i.e., 2012-2016 and 2002-2016, respectively. The proportion of patents with tumour stage IV ranged from 22% in Stockholm area to 31% in Middle Norrland, while at the healthcare region level it was lowest in Stockholm healthcare region (23%) and highest in North (30%) and Uppsala-Örebro (29%) healthcare regions.Conclusion: There are considerable geographical variations in the incidence and tumour stage distribution of oesophageal cancer in Sweden.

Associations of sedentary behavior in leisure and occupational contexts with symptoms of depression and anxiety

Sedentary behaviors (SB) can be associated with poorer mental health, but it remains unclear whether contexts for these behaviors may be important. We assessed relationships of SB in leisure-time and occupational contexts with frequent symptoms of depression and anxiety. Data originate from the Swedish Health Profile Assessment (HPA) database, a health assessment offered to employees working for companies or organizations connected to healthcare services. Analyses are based on data from 2017 onwards (N = 23,644; 57% male, mean age = 42 years). Two self-report questions assessed proportions of time spent in SB in leisure contexts and in the occupational setting. Logistic regressions examined relationships of SB in each context with the self-reporting of frequent symptoms of depression/anxiety. A separate model for the leisure plus occupational SB was also generated. Fully-adjusted models included exercise frequency. Compared to those reporting that they were 'almost never' sedentary in leisure-time contexts, a detrimental dose-response with frequent depression/anxiety symptoms was observed with increasing proportions of sedentary time: 50% of the time (OR = 1.44; 1.23-1.70), 75% (OR = 2.95; 2.45-3.54), almost always (OR = 3.85; 2.84-5.22). For occupational SB, the only associations were among those who reported being sedentary almost always, compared to almost never (OR = 1.47; 1.25-1.73). Associations of 'overall' SB with depression/anxiety symptoms mirrored the dose-response relationship for leisure-time SB. Exercise frequency attenuated the association for leisure-time SB only, but it remained statistically significant. Adults who spend ≥50% of their leisure-time in sedentary pursuits experience more frequent symptoms of depression and anxiety, compared to those who are less sedentary in that context.

Active commuting in Swedish workers between 1998 and 2015-Trends, characteristics, and cardiovascular disease risk

Background

Trend analyses of active commuting and potential variations in trends and association with cardiovascular disease (CVD) risk within subgroups are unknown.

Objectives

To (a) describe trends in active commuting between 1998 and 2015 and (b) to study the association between different amounts of active commuting and the incidence risk of CVD in a large sample of Swedish workers, and analyses of potential variations across subgroups of socio‐demographics, physical activity, and BMI.

Methods

A total of 318 309 participants (47% women, 18‐74 years) who participated in a nationwide occupational health service screening between 1998 and 2015 were included. Commuting habits were self‐reported, and data on first‐time CVD events were derived from national registers.

Results

Self‐reported passive commuters decreased between 1998 and 2015 (64% to 56%), transferring to an increase in mainly moderate/high‐dose active commuters (12% to 19%). Changes were seen in all subgroups. The characteristics and lifestyle habits of the typical passive and active commuter changed little over the study period. Low‐ and moderate/high‐dose active commuters had significantly decreased risks for a first time CVD during follow‐up. This was accentuated in men, middle‐aged, and in participants with light physical work situations, irregular exercise habits, being overweight/obese, and with low fitness.

Conclusion

Increases in active commuting were observed between 1998 and 2015, however still leaving a majority who do not actively commute. As active commuting, regardless dose, is associated with a lower CVD risk, encouraging more people to actively commute may provide an easily accessible and time‐efficient possibility to increase physical activity and health in the general population.

Suicide among persons who entered same-sex and opposite-sex marriage in Denmark and Sweden, 1989-2016: a binational, register-based cohort study

BACKGROUND

People belonging to sexual minority groups have higher levels of suicidality than heterosexuals. However, findings regarding suicide death are sparse. Using unique national data from two countries, we investigated whether individuals entering a same-sex marriage (SSM), a proxy group of sexual minority individuals, had higher suicide rates than those entering opposite-sex marriage (OSM).

METHODS

A cohort study of all males and females who entered an SSM (n=28 649) or OSM (n=3 918 617) in Denmark and Sweden during 1989-2016 was conducted. Incidence rate ratios (IRRs) for suicide were calculated using adjusted Poisson regression models.

RESULTS

In total, 97 suicides occurred among individuals who had entered an SSM compared with 6074 among those who entered an OSM, corresponding to an adjusted IRR of 2.3 (95% CI 1.9 to 2.8). For people who entered SSM, a 46% decline was noted over time from an IRR of 2.8 (95% CI 1.9 to 4.0) during 1989-2002 to 1.5 (95% CI 1.2 to 1.9) during 2003-2016. The excess suicide mortality was present in all age groups but most pronounced among younger individuals aged 18-34 years of age (IRR 2.7, 95% CI 1.5 to 4.8) and females (IRR 2.7, 95% CI 1.8 to 3.9).

CONCLUSION

This large register-based study found higher suicide rates among individuals who entered an SSM, compared with those who entered an OSM. A lower suicide rate was noted for individuals in SSMs in recent years. More research is needed to identify the unique suicide risk and protective factors for sexual minority people.

Sex- and age-specific associations between cardiorespiratory fitness, CVD morbidity and all-cause mortality in 266.109 adults

The aim was to investigate sex- and age-specific associations between cardiorespiratory fitness, all-cause and cause-specific mortality, and cardiovascular disease (CVD) morbidity. 266.109 participants (47% women, 18-74 years) free from CVD, participating in occupational health service screenings in 1995-2015 were included. CRF was assessed as estimated maximal oxygen consumption (estVO₂max) using a submaximal cycle test. Incident cases of first-time CVD event and death from any cause were ascertained through national registers. There were 4244 CVD events and 2750 cases of all-cause mortality during mean 7.6 years follow-up. Male gender, higher age and lower estVO₂max were associated with higher all-cause mortality and CVD morbidity incidence rates. Risk reductions with increasing estVO₂max were present in all age-groups of men and women. No obvious levelling off in risk was identified in the total cohort. However, women and older age-groups showed no further reduction in higher aggregated estVO₂max levels. CVD specific mortality was more associated with estVO₂max compared to tumor specific mortality. The risk for all-cause mortality and CVD morbidity decreased by 2.3% and 2.6% per increase in 1 ml·min^-1·kg^-1 with no significant sex-differences but more pronounced in the three lower estVO₂max categories for all-cause mortality (9.1%, 3.8% and 3.3%, respectively). High compared to lower levels of estVO₂max was not related to a significantly elevated mortality or morbidity. In this large cohort study, CVD morbidity and all-cause mortality were inversely related to estVO₂max in both men and women of all age-groups. Increasing cardiorespiratory fitness is a clear public health priority.

Elevated non-esterified fatty acids impair survival and promote lipid accumulation and pro-inflammatory cytokine production in bovine endometrial epithelial cells

Elevated non-esterified fatty acids (NEFAs) are associated with negative effects on bovine theca, granulosa and oviductal cells but the effects of NEFAs on bovine endometrial epithelial cells (bEECs) are not as well documented. The objective of this study was to define the effects of NEFAs on bEECs. Postprimary bEECs were treated with 150, 300 or 500µM of either palmitic acid (PA), stearic acid (SA) or oleic acid (OA) or a mixture of NEFAs (150µM of each FA) or 0.5% final concentration of vehicle ethanol (control). Viability and proliferation of bEECs exposed to 150µM of each NEFA or a mixture of NEFAs were unaffected. Increased lipid accumulation was found in all treated groups (P<0.01). In cells exposed to 500µM of each NEFA and 300µM PA decreased cell viability (P<0.001), proliferation (P<0.05) and increased apoptosis (P<0.05) were observed. Treatment with 500µM OA, PA and SA had the strongest effects on cell viability, proliferation and apoptosis (P<0.05). Treatment with PA and OA increased interleukin-6 (IL-6) concentrations (P<0.05), whereas only the highest concentration of PA, OA and SA stimulated IL-8 production (P<0.05). These results suggest that high concentrations of NEFAs may impair endometrial function with more or less pronounced effects depending on the type of NEFA and time of exposure.

Education, Gender, and Cohort Fertility in the Nordic Countries

Systematic comparisons of fertility developments based on education, gender and country context are rare. Using harmonized register data, we compare cohort total fertility and ultimate childlessness by gender and educational attainment for cohorts born beginning in 1940 in four Nordic countries. Cohort fertility (CTF) initially declined in all four countries, although for cohorts born in the 1950s and later, the CTF remained stable or declined only modestly. Childlessness, which had been increasing, has plateaued in Denmark, Norway and Sweden. Women's negative educational gradient in relation to total fertility has vanished, except in Finland, while men's positive gradient has persisted. The highest level of men's childlessness appears among the least educated. In the oldest female cohorts, childlessness was highest among the highly educated, but these patterns have changed over the cohorts as childlessness has increased among the low educated and remained relatively stable among higher educated women. In Denmark, Norway and Sweden, childlessness is now highest among the least educated women. We witness both a new gender similarity and persistent (among men) and new (among women) educational disparities in childbearing outcomes in the Nordic region. Overall, the number of low educated has decreased remarkably over time. These population segments face increasing social and economic disadvantages that are reflected as well in their patterns of family formation.

Fecundity and human birth seasonality in Sweden: a register-based study

BACKGROUND

It is well-established that couples' fecundities vary widely. Each couple has a relatively constant monthly probability of conceiving, which can vary from zero to quite high. This underlying probability is usually expressed as the time (number of menstrual cycles) the couple requires to conceive. Couples with high fecundity will, on average, need fewer cycles than couples with low fecundity. It is also well-documented that almost all human populations exhibit seasonal variation in births. Most European countries show seasonal variation that usually peak in the spring and are the lowest during the last quarter of the year. The increasingly strong pattern of depressed birth rates in November and December is likely explained by the December-January cut-off threshold for Swedish pupils' school entry and their parents increasing awareness of the negative effects on school outcomes for children who are juniors in the school-entry cohort they belong to. To actively plan births for a specific time of the year, couples need to have some knowledge of the time required for them to conceive.

METHODS

We use the duration between marriage of childless couples and first birth as a proxy measure of couples' fecundity. Based on this time-to-pregnancy measure we study to what extent couples' capacity to conceive affects the seasonality of their second births. We hypothesize that in a society with highly controlled fertility and a strong norm of having at least two children, sub-fertile couples will on average show less seasonal variation in second births. Sub-fertile couples, requiring more time to conceive the first time, will be less likely to try to target a desired birth month for their second child because doing so could jeopardize fulfilling their desired family size. We apply multinomial logistic regressions on 81,998 Swedish couples who married while being childless and subsequently gave birth to at least two children between 1990 and 2012, to investigate fecundity's role in seasonal variation in second births.

RESULTS

We found that seasonal variation in second births was strongly associated with couples' observed fecundity, measured as the duration between marriage formation and first birth. Our results support the hypothesis that sub-fertile couples, requiring more time to conceive the first time, show less seasonal variation in second births. The seasonal variations in second order births among couples with normal fecundity shows some similarities to traditional patterns as seen in agricultural and industrial societies of the past, with high numbers of births during the spring, and low numbers during the last quarter of the year. However, two important differences are notable. The characteristic Christmas peak in September has vanished, and the low birth rates in November and December come out much stronger than in the past.

CONCLUSIONS

The birth seasonality among couples with normal fecundity are what we would expect if couples actively plan their births according to the cut-off date for Swedish pupils' school entry. We argue that our findings support the notion that scheduled childbirth is a reality in contemporary sociality.

Decline in cardiorespiratory fitness in the Swedish working force between 1995 and 2017

Background

Long‐term trend analyses of cardiorespiratory fitness (VO₂max) in the general population are limited.

Objectives

To describe trends in VO₂max from 1995 to 2017 in the Swedish working force and to study developments across categories of sex, age, education, and geographic regions.

Methods

A total of 354 277 participants (44% women, 18‐74 years) who participated in a nationwide occupational health service screening between 1995 and 2017 were included. Changes in standardized mean values of absolute (L/min) and relative (mL/min/kg) VO₂max, and the proportion with low (<32) relative VO₂max are reported. VO₂max was estimated using a submaximal cycle test.

Results

Absolute VO₂max decreased by −6.7% (−0.19 L/min) in the total population. Relative VO₂max decreased by −10.8% (−4.2 mL/min/kg) with approximately one‐third explained by a simultaneous increase in body mass. Decreases in absolute fitness were more pronounced in men vs women (8.7% vs 5.3%), in younger vs older (6.5% vs 2.3%), in short (11.4%) vs long (4.5%) education, and in rural vs urban regions (6.5% vs 3.5%), all P < 0.001. The proportions with low VO₂max increased from 27% to 46% (P < 0.001).

Conclusion

Between 1995 and 2017, there was a steady and pronounced decline in mean cardiorespiratory fitness in Swedish adults. Male gender, young age, short education, and living in a rural area were predictive of greater reductions. The proportion with low cardiorespiratory fitness almost doubled. Given the strong associations between cardiorespiratory fitness and multiple morbidities and mortality, preventing further decreases is a clear public health priority, especially for vulnerable groups.

Changing seasonal variation in births by sociodemographic factors: a population-based register study

STUDY QUESTION

Have seasonal variations in births by factors related to maternal education, age, parity and re-partnering changed over a 72-year period?

SUMMARY ANSWER

Seasonal variation in births has been reduced overall but also changed its pattern over the last seven decades.

WHAT IS KNOWN ALREADY

The number of births varies markedly by season, but the causes of this variation are not fully understood. Seasonality of births is, in some populations, strongly influenced by sociodemographic factors.

STUDY DESIGN SIZE DURATION

A longitudinal study design was used by analysing the seasonal variation in live births between 1940 and 2012, and relating it to mothers' sociodemographic characteristics at the time of childbirth (maternal education, age, parity and re-partnering).

PARTICIPANTS/MATERIALS SETTING METHODS

Register data on 6 768 810 live births in Sweden between 1940 and 2012 were used. Information on biological parents are available for more than 95% of all births. Multinomial logistic regressions were used to calculate predicted probabilities of giving birth for each calendar month.

MAIN RESULTS AND THE ROLE OF CHANCE

Between 1940 and 1999, Swedish birth rates showed the typical seasonal variation with high numbers of births during the spring, and low numbers of births during the last quarter of the year. However, during the 21st century, the seasonal variation in fertility declined so that only minor variation in birth rates between February and September now remains. Still, the pattern of low birth rates at the end of the year remains and has even become more pronounced from the 1980s onwards. The characteristic 'Christmas effect' that used to be visible in September has vanished over the last 30 years. The roles in seasonal variation of maternal education, the mother's age, parity and instances where the mother has re-partnered between subsequent births changed during the second half of the 20th century. From 1980s onwards, the decline in birth rates during the last quarter of the year became particularly pronounced among highly educated mothers. Over the 72 years studied, the seasonal variation among first-time mothers declined steadily and has almost disappeared at the end of the study period. Using data that cover ~180 000 births in each month, all meaningful results are statistically significant.

LIMITATIONS REASONS FOR CAUTION

The study uses data from one Nordic country only, making it difficult to draw conclusions that may hold for other countries.

WIDER IMPLICATIONS OF THE FINDINGS

The typical seasonal variation reported for Sweden between 1940 and 1999, with high numbers of births during the spring and low numbers of births during the last quarter of the year, is in line with results from most other European countries during the same time period. However, the significant decline in seasonal variation in the early 21st century is a novel development. The study underlines that in a society with low fertility and efficient birth control, active choices and behaviours associated with an individual's sociodemographic characteristics tend to matter more for the seasonal timing of childbearing than environmental factors related to the physiological ability to reproduce and cultural-behavioural factors related to the frequency of intercourse.

STUDY FUNDING/COMPETING INTERESTS

The study was funded by the Swedish Research Council (Vetenskapsrådet) via the Swedish Initiative for Research on Microdata in the Social and Medical Sciences (SIMSAM): Stockholm University SIMSAM Node for Demographic Research (grant registration number 340-2013-5164). The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

Higher divorce risk when mates are plentiful? Evidence from Denmark

Work from social and biological sciences has shown that adult sex ratios are associated with relationship behaviours. When partners are abundant, opportunities for mate switching may increase and relationship stability decrease. To date, most of the human literature has used regional areas at various levels of aggregation to define partner markets. But, in developed countries, many individuals of reproductive age spend a considerable amount of time outside their residential areas, and other measures may better capture the opportunities to meet a (new) partner. Here, we use Danish register data to test whether the sex ratio of the occupational sector is linked to divorce. Our data cover individuals in Denmark who married during 1981-2002 and we control for age at and duration of marriage, education and parity. Results support the prediction that a higher proportion of opposite-sex individuals in one's occupational sector is associated with higher divorce risk. This holds for both men and women, but associations are somewhat stronger for men and vary by education. Our results highlight the need to study demographic behaviours of men and women simultaneously, and to consider partner markets beyond geographical areas so that differing strategies for males and females may be examined.

Correction to: Compressive loading of the murine tibia reveals site-specific micro-scale differences in adaptation and maturation rates of bone

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