During early adulthood, a phase in which the central nervous system displays considerable plasticity and in which important cognitive traits are shaped, the effects of exercise on cognition remain poorly understood. We performed a cohort study of all Swedish men born in 1950 through 1976 who were enlisted for military service at age 18 (N ‫؍‬ 1,221,727). Of these, 268,496 were full-sibling pairs, 3,147 twin pairs, and 1,432 monozygotic twin pairs. Physical fitness and intelligence performance data were collected during conscription examinations and linked with other national databases for information on school achievement, socioeconomic status, and sibship. Relationships between cardiovascular fitness and intelligence at age 18 were evaluated by linear models in the total cohort and in subgroups of full-sibling pairs and twin pairs. Cardiovascular fitness, as measured by ergometer cycling, positively associated with intelligence after adjusting for relevant confounders (regression coefficient b ‫؍‬ 0.172; 95% CI, 0.168 -0.176). Similar results were obtained within monozygotic twin pairs. In contrast, muscle strength was not associated with cognitive performance. Cross-twin cross-trait analyses showed that the associations were primarily explained by individual specific, non-shared environmental influences (>80%), whereas heritability explained <15% of covariation. Cardiovascular fitness changes between age 15 and 18 y predicted cognitive performance at 18 y. Cox proportional-hazards models showed that cardiovascular fitness at age 18 y predicted educational achievements later in life. These data substantiate that physical exercise could be an important instrument for public health initiatives to optimize educational achievements, cognitive performance, as well as disease prevention at the society level.aerobic fitness ͉ intelligence ͉ muscular strength ͉ twin analysis ͉ exercise

Hairdressers are highly exposed to skin-damaging substances. The self-reported incidence of hand eczema was substantially higher in female hairdressers than in controls from the general population and than that found previously in register-based studies. For many individuals, onset of hand eczema occurs early in life. Only about 10% of the hand eczema cases among hairdressers would be prevented if no one with skin atopy entered the trade.

Few studies have investigated the relationship between vehicle exhaust and the new onset of asthma among adults. The aim of the present prospective cohort study was to investigate the relationship between the cumulative incidence of asthma and onset of asthma among adults and vehicle exhaust concentrations at home.Participants from three Swedish cities included in the Respiratory Health in Northern Europe cohort constituted the study population. Exposure at each participant's home was calculated using dispersion models. We also used ,50 m distance to nearest major road as a more simple indicator of exposure. The adjusted model included 3,609 participants, of which 107 were classified as onset cases and 55 as true incident cases of asthma.There was a positive association between asthma onset (odds ratio (OR) per 10 mg?m -3 1.46, 95% confidence interval (CI) 1.07-1.99) and incident asthma (OR per 10 mg?m -3 1.54, 95% CI 1.00-2.36) and the levels of nitrogen dioxide (NO 2 ), which remained statistically significant after adjusting for potential confounders. The relationship between asthma and NO 2 was not significantly modified by sex, hay fever or wheeze. The risk of developing asthma was also significantly related to living close to a major road. The current study suggests that elevated levels of vehicle exhaust outside the home increase the risk of onset and incident asthma among adults.

Background:Working as a hairdresser involves exposure to a variety of chemical agents.Aims:To estimate the risk of such exposure in relation to reproductive outcome.Methods:A cohort of hairdressers, certified in Sweden from 1970 onwards, and a referent cohort of women from the general population were established and linked to the Swedish Medical Birth Register for the period 1973 to 1994. In the cohort of hairdressers 3706 women gave birth to 6960 infants. The corresponding numbers among the referents were 3462 and 6629. Questionnaires were sent to all hairdressers to obtain individual exposure data. The response rate was 65%.Results:Compared with the referents, the hairdressers more often gave birth to infants that were small for gestational age (SGA). In addition, a higher fraction of the infants born to a hairdresser had a major malformation (2.8%v2.1%). Frequent permanent waving and spraying tended to be associated with increased risk of having an SGA infant, whereas no clear association could be seen between the individual exposure assessments and malformation risk.Conclusions:Results indicated that hairdressers have a slight increased risk of having intrauterine growth retarded infants and infants with major malformation compared with women from the general population. However, no clear associations were seen between individual exposure assessments and these outcomes.

Stroke afflicts ≈1 in 6 people in their lifetime, 1 causing 6.2 million deaths worldwide.2 To improve stroke prevention, knowledge of key risk factors, especially those that are modifiable such as physical activity, is essential. In middle-aged men 3 and women, 4 it has been shown that higher levels of physical activity are associated with reduced risk of future ischemic stroke (IS). Specifically, in 2 meta-analyses on 16 original studies of middle-aged men and women undertaking more intensive versus lower levels of physical activity, the overall risk reduction was 19% to 27%. 5,6 However, in these and most other such studies, physical activity is assessed by self-report in questionnaires and interviews in large numbers of subjects, yet it has been shown that self-report leaves the true degree of physical activity vulnerable to bias. 7Aerobic or cardiovascular fitness (henceforth fitness), however, can be measured objectively. Although measurement requires relatively time-consuming ergometric tests, and so has generated fewer observations and studies, it has been shown to be a more accurate predictor of cardiovascular risk Background and Purpose-Low cardiovascular fitness (fitness) in mid-and late life is a risk factor for stroke. However, the respective effects on long-term stroke risk of fitness and muscle strength in early adulthood are unknown. Therefore, we analyzed these in a large cohort of young men. There were stronger associations for fatal stroke. All 3 stroke types displayed similar associations. Associations between fitness and stroke remained when adjusted for muscle strength, whereas associations between muscle strength and stroke weakened/disappeared when adjusted for fitness. Conclusions-At the age of 18 years, low fitness and to a lesser degree low muscle strength were independently associated with an increased future stroke risk.