Katya M. Herman

Tracking of obesity and physical activity from childhood to adulthood: The Physical Activity Longitudinal Study

OBJECTIVE Body mass index (BMI) has shown moderate to strong stability through childhood into adulthood, while physical activity (PA) tracks less well. Tracking studies have often had limited follow-up lengths. The aim was to investigate BMI and PA tracking over 22 years from youth to adulthood. METHODS Subjects included 374 participants aged 7 to 18 years in the 1981 Canada Fitness Survey, who were re-evaluated in 2002-04. The stability of BMI and leisure-time PA energy expenditure (AEE) was assessed by inter-age correlations, maintenance of extreme quintiles and BMI status, and the prediction of adult overweight from youth BMI. RESULTS BMI tracking was moderate to strong (r=0.42-0.65) in females, and moderate (r=0.29-0.53) in males. Approximately 38% and 42% of youth in the highest and lowest BMI quintiles, respectively, remained in these quintiles as adults. About 83% of overweight youth remained overweight as adults, while 85% of overweight adults were not overweight youth. Almost all healthy weight adults had been healthy weight youth. The odds of being overweight in adulthood was 6.2 times greater (95% CI: 2.2-17.2) in overweight compared with healthy weight youth. PA tracking over 22 years was low and non-significant, but moderate over the final 15 years. Only 16% and 18% of youth in the highest and lowest PA quintiles, respectively, remained in these quintiles as adults. CONCLUSIONS BMI, but not PA, tracked well over 22 years in this sample. The majority of overweight youth remained overweight as adults; however, the majority of overweight adults were not overweight youth.

Physical activity, body mass index, and health-related quality of life in Canadian adults.

PURPOSE Physical activity (PA) positively influences health-related quality of life (HRQL), whereas obesity is associated with significant HRQL impairments. Active-obese persons often have similar or lower risk of cardiovascular outcomes and mortality than inactive-healthy weight persons; however, the combined PA-weight status effects on HRQL are unclear. The aim was to investigate the combined association of PA and body mass index (BMI) with HRQL in Canadian adults and older adults. METHODS Cross-sectional data included 110,986 participants ≥ 18 yr from the 2005 Canadian Community Health Survey, representing an estimated 22,563,527 Canadians. HRQL indicators included: Self-Rated Health (SRH), Participation and Activity Limitation due to illness/injury (PAL), and Total Disability Days (physical + mental) during the past 14 d (TDD). Prevalence of adverse HRQL was estimated by BMI, PA, and combined BMI-PA categories. Adjusted logistic regression was used to assess the odds of adverse HRQL by BMI, PA, and BMI-PA. Analyses were stratified by sex and age (18-44, 45-64, ≥65 yr). RESULTS In both men and women of all ages, inactive individuals had greater likelihood of fair/poor SRH, and sometimes/often PAL, at all BMI levels; conversely, in active individuals, being underweight, overweight, or obese had little effect on SRH and PAL. Associations were weaker for TDD, where the greatest influence was in older adults from inactivity combined with underweight. Overweight showed less association to HRQL in males and older adults, whereas underweight showed stronger association in males and older adults. CONCLUSIONS When examining BMI-PA in combination, PA emerges as the more important correlate of HRQL, regardless of weight status. This reinforces the importance of PA to health outcomes over and above the benefits related to weight loss or maintenance.

Physical activity, screen time and self-rated health and mental health in Canadian adolescents.

OBJECTIVE Physical activity (PA) and screen time (ST) are associated with self-rated health (SRH) in adults; however, SRH has been less studied among youth, and information about self-rated mental health (SRMH) is lacking. This study examined the associations of PA and ST with SRH and SRMH among adolescents. METHODS Cross-sectional data from the 2011-2012 Canadian Community Health Survey included 7725 participants aged 12-17years, representing 1,820,560 Canadian adolescents. Associations of self-reported PA and ST to SRH and SRMH were assessed, controlling for age, race/ethnicity, smoking, highest household education and weight status. RESULTS Excellent/very good SRH was reported by 78% of active vs. 62% of inactive adolescents, and 77% of those meeting vs. 70% of those exceeding ST guidelines (both p<0.001). Excellent/very good SRMH was reported by 81% of active vs. 76% of inactive adolescents, and 84% of those meeting vs. 78% of those exceeding ST guidelines (both p<0.001). Inactive adolescents had twice higher odds of sub-optimal SRH, and inactive girls had 30% greater odds of sub-optimal SRMH. Adolescents exceeding 2h/day ST had 30% greater odds of sub-optimal SRH, and 30-50% greater odds of sub-optimal SRMH. CONCLUSION PA and ST are independently associated with health perceptions among Canadian adolescents. Interventions should consider health perceptions in addition to biomedical outcomes.

Sedentary behavior in a cohort of 8- to 10-year-old children at elevated risk of obesity

OBJECTIVES Sedentary behavior (SB) is distinct from physical inactivity. Childrens guidelines recommend ≤2h/day screen time and ≥60min/day moderate-to-vigorous physical activity (MVPA). This study describes SB in children at elevated risk of obesity, including the possibility of high SB in otherwise active children. METHODS Participants were 534 children from Quebec, Canada, aged 8-10years with ≥1 obese parent in 2005-2008. SB and MVPA were measured by accelerometer and specific SBs by self-report, and height and weight were directly measured. RESULTS Overweight/obese children were significantly more sedentary overall and reported higher screen time than normal weight children. About 19% of boys and 46% of girls met screen time but not PA guidelines; 28% of boys and 5% of girls met PA but not screen time guidelines. About 46% of overweight/obese children met neither guideline (32% normal weight); only 5% overweight/obese children met both (21% normal weight). Reported behaviors contributed 60%-80% of total SB time; the most sedentary children had the most unaccounted for SB time. CONCLUSIONS Overweight/obese children are more sedentary overall and report higher screen time than normal weight children. Public health efforts targeting PA and SB in children must consider sex and weight status while being cognizant that being sufficiently active is not exclusive of high levels of SB.

Self-Rated Health in Children at Risk for Obesity: Associations of Physical Activity, Sedentary Behavior, and BMI

BACKGROUND Self-rated health (SRH) is a common indicator of health-related quality of life; however, little is known about SRH in children. This study explored the associations of physical activity (PA), sedentary behavior (SED), and BMI with SRH in children at risk for obesity. METHODS Participants were 527 children aged 8-10 years in the Quebec Adipose and Lifestyle Investigation in Youth study (inclusion criteria: ≥ 1 parent clinically obese). PA and SED were measured by accelerometer, specific SED behaviors by self-report, and height and weight measured. RESULTS About 40% of children were overweight or obese; 48% reported less-than- excellent health. The odds of reporting less-than-excellent health were higher among obese girls (OR 3.0, 95% CI 1.4-5.2) and boys (OR 2.7, 95% CI 1.5-6.1) versus healthy weight children. Boys not meeting PA guidelines and boys in the lowest moderate-to-vigorous PA tertile were at 2 and 6 times higher odds of less-than-excellent SRH, respectively, versus more active boys. In girls, higher computer/video time and reading time were associated with higher and lower odds of less-than-excellent SRH, respectively. CONCLUSIONS Obesity is inversely associated with SRH in boys and girls, PA is positively associated with SRH in boys, and SED behaviors are associated with SRH in girls.

Combined Physical Activity/Sedentary Behavior Associations With Indices of Adiposity in 8- to 10-Year-Old Children

OBJECTIVE Individuals may achieve high physical activity (PA) yet also be highly sedentary (SED). This study assessed adiposity in children classified by PA/SED groups. METHODS Participants were 520 8- to 10-year-old children with ≥ 1 obese parent. Moderate-to-vigorous PA (MVPA) and SED were measured by accelerometer, and screen-time was measured by self-report. Height, weight, waist circumference (WC), body fat percentage (BF%), and VO2peak were objectively measured; energy intake was measured by dietary recall. Elevated adiposity was defined as BMI ≥ 85th percentile, WC ≥ 90th percentile, BF% ≥ 85th percentile, or waist-to-height ratio (WHR) ≥ 0.5. RESULTS Up to 27% of boys and 15% of girls were active/SED. Adiposity was lowest for active/non-SED, highest for inactive/SED, and intermediate and similar for active/SED and inactive/non-SED. Using 60 min/d MVPA and 2 h/d screen-time cut-offs, prevalence ranges for elevated adiposity in the active/non-SED, active/SED, inactive/non-SED, and inactive/SED groups were 0% to 14%, 15% to 44%, 16% to 40%, and 32% to 51%, respectively. Corresponding odds and 95% confidence intervals of being overweight/obese for the latter groups were 3.8 (95% CI, 1.7-8.4), 3.8 (1.8-8.2), and 4.9 (2.3-10.3) versus active/non-SED. PA/SED-adiposity associations were mediated by fitness but not energy intake. CONCLUSIONS Combined PA/SED levels are strongly associated with adiposity in children, but associations are mediated by fitness. Active children who accumulate >2 h/d of screen time and inactive children are equally likely to be overweight/obese.

Smoking and multiple sclerosis: A systematic review and meta-analysis using the Bradford Hill criteria for causation☆

BACKGROUND Despite being one of the most common neurological disorders globally, the cause(s) of multiple sclerosis (MS) remain unknown. Cigarette smoking has been studied with regards to both the development and progression of MS. The Bradford Hill criteria for causation can contribute to a more comprehensive evaluation of a potentially causal risk factor-disease outcome relationship. The objective of this systematic review and meta-analysis was to assess the relationship between smoking and both MS risk and MS progression, subsequently applying Hills criteria to further evaluate the likelihood of causal associations. METHODS The Medline, EMBASE, CINAHL, PsycInfo, and Cochrane Library databases were searched for relevant studies up until July 28, 2015. A random-effects meta-analysis was conducted for three outcomes: MS risk, conversion from clinically isolated syndrome (CIS) to clinically definite multiple sclerosis (CDMS), and progression from relapsing-remitting multiple sclerosis (RRMS) to secondary-progressive multiple sclerosis (SPMS). Dose-response relationships and risk factor interactions, and discussions of mechanisms and analogous associations were noted. Hills criteria were applied to assess causality of the relationships between smoking and each outcome. The effect of second-hand smoke exposure was also briefly reviewed. RESULTS Smoking had a statistically significant association with both MS risk (conservative: OR/RR 1.54, 95% CI [1.46-1.63]) and SPMS risk (HR 1.80, 95% CI [1.04-3.10]), but the association with progression from CIS to CDMS was non-significant (HR 1.13, 95% CI [0.73-1.76]). Using Hills criteria, there was strong evidence of a causal role of smoking in MS risk, but only moderate evidence of a causal association between smoking and MS progression. Heterogeneity in study designs and target populations, inconsistent results, and an overall scarcity of studies point to the need for more research on second-hand smoke exposure in relation to MS prior to conducting a detailed meta-analysis. CONCLUSION This first review to supplement systematic review and meta-analytic methods with Hills criteria to analyze the smoking-MS association provides evidence supporting the causal involvement of smoking in the development and progression of MS. Smoking prevention and cessation programs and policies should consider MS as an additional health risk when aiming to reduce smoking prevalence in the population.

Association Between Accelerometer-Measured Physical Activity Intensities and Sedentary Time in 8- to 10-Year-Old Children

This study examines the association between objectively-measured physical activity (PA) intensities and sedentary behavior (SED) in a cohort of 532 children aged 8-10 y. PA and SED were assessed by accelerometer over 7-days. Television and computer/video-game use were self-reported. Associations between PA intensities and SED variables were assessed by Spearman correlations and adjusted multiple linear regression. Higher mean daily moderate-to-vigorous and vigorous PA (MVPA, VPA) were negatively associated with mean daily SED (r = -0.47 and -0.37; p < .001), and positively associated with mean daily total PA (r = .58 and 0.46; p < .001). MVPA was also positively associated with light PA (LPA; r = .26, p < .001). MVPA and VPA were not significantly associated with TV, computer/video or total screen time; accelerometer SED was only weakly associated with specific SED behaviors. On average, for each additional 10 min daily MVPA, children accumulated >14 min less SED, and for each additional 5 min VPA, 11 min less SED. Thus, over the course of a week, higher mean daily MVPA may displace SED time and is associated with higher total PA over and above the additional MVPA, due to concomitant higher levels of LPA. Public health strategies should target both MVPA and SED to improve overall PA and health in children.

Correlates of sedentary behaviour in 8- to 10-year-old children at elevated risk for obesity.

The purpose of this study was to describe correlates of sedentary behaviour (SED) in children at elevated risk of obesity because of parental obesity. Participants were 534 children aged 8-10 years with ≥ 1 obese parent. SED and physical activity (PA) were measured by accelerometer, screen time by self-report, and height, weight, waist circumference, and cardiovascular fitness objectively measured. Data describing the child, parents, friends, and home and neighbourhood environments were from child self-report. Higher total SED time was significantly positively associated with childs age, mothers age, Tanner stage, weight status or waist circumference, less self-reported PA, choosing screen time over PA/sport, mother saying PA/sport good for them, and fewer weekly physical education (PE) classes. Exceeding 2 h/day screen time was significantly associated with childs age, male sex, weight status or waist circumference, choosing screen time over PA/sport, and dinnertime TV viewing. Children regularly watching TV with dinner had 2.3 times greater odds (95% confidence interval (CI) 1.52, 3.58) of exceeding screen time guidelines compared with children rarely watching TV with dinner; children reporting ≤ 2 PE classes/week had 2.4 times greater odds (95% CI 1.41, 4.10) of being in the highest SED tertile compared with children reporting >2 PE classes/week. Hence, the most sedentary children are older, more biologically mature, less active, more overweight/obese, have fewer PE classes, and are more likely to choose screen time over PA and watch TV with dinner compared with less sedentary children. PE opportunities and mealtime TV viewing are potentially modifiable targets for reducing total SED and screen time in children.

Physical activity and sitting time in bariatric surgery patients 1-16 years post-surgery.

Physical activity (PA) is an important adjunct to bariatric surgery in the treatment of severe obesity; however, patient PA levels prior to and in the short‐term following surgery are usually low. Scarce data exist describing PA and sedentary behaviours in the long term following surgery. The objectives were to describe PA and sitting time in bariatric patients 1–16 years post‐surgery and assess their associations with patient, surgery and weight‐loss characteristics. A total of 398 bariatric patients (73% female; mean age 47 ± 11 years, mean 6 ± 4 years since surgery) completed a telephone questionnaire. Patients reported moderate‐to‐vigorous PA (MVPA: # sessions week−1 ≥30 min), sitting time (h d−1) and change in PA and sitting time vs. pre‐surgery (more/same/less). Associations with patient, surgery and weight‐loss characteristics were assessed. Only 53% of patients reported ≥1 session week−1 MVPA, mean sitting time was 7 ± 4 h d−1, 74% of patients reported more PA and 53% reported less sitting, now vs. pre‐surgery. Age, sex, smoking status, pre‐surgery body mass index, time‐since‐surgery and percent excess weight lost were significantly associated with PA and/or sitting outcomes. Patients currently experiencing ≥50% excess weight loss had over three times the odds of reporting ≥1 session week−1 MVPA (odds ratio [95% confidence interval] 3.28 [1.57, 6.89]) and almost four times greater odds of reporting ‘more’ PA vs. pre‐surgery (3.78 [2.15, 6.62]) compared with their less successful counterparts. Results point to low PA and high sedentariness among bariatric patients in the long‐term following surgery, associated with several characteristics. Associations with long‐term weight management highlight the need for tailored interventions to promote active living in this patient population.