ABSTRACT
Objective: To examine the validity of accelerometers for characterizing habitual physical activity patterns in Indian children. Design: Cohort study. Setting: Holdsworth Memorial Hospital, Mysore. Subjects: Children (N=103, mean age 6.6 years) selected from an ongoing birth cohort study. Methods: Physical activity was measured over 7 days using accelerometers (MTI Actigraph) and concurrent parent-maintained activity diaries. Actigraph counts per minute representing sedentary (<10), light (<400), moderate (<3000) and vigorous (≥3000) activity were determined using a structured activity session in a separate group of 10 children. In 46 children chosen for validating accelerometers, time spent in different activity levels according to diaries was determined. Energy Expenditure (EE) was calculated from diaries using a factorial method. Results: Ninety-eight children wore the monitor for ≥4 days. Total counts and time spent in different activity levels were similar in boys and girls (P>0.2). Among 46 children chosen for comparisons, time spent in sedentary (r =0.48, P=0.001), light (r=0.70, P<0.001) and moderate activities (r=0.29, P=0.054) according to diaries correlated with those derived from counts, and total Actigraph counts correlated with EE (r=0.42, P=0.004). Bland-Altman analysis showed systematic bias, and wide limits of agreement between these methods for time spent in different activity levels. Conclusions: Accelerometers are a well tolerated and objective way of measuring activity behavior in free-living children. Though accelerometer counts correlate with time spent in activity of varying intensity and energy expenditure derived from parent-maintained diaries, wide limits of agreement show that the limitations of accelerometers need to be recognized in interpreting the data that they generate.
ABSTRACT
In Trinidad and Tobago, cardiovascular disease and Type 2 diabetes mellitus are important causes of morbidity and mortality, and birth weight is significantly less than reference standards. Lower birth weight is associated with increased risk of these diseases. Variation in birth weight is due, in part, to deposition of adipose tissue in the foetus during the last trimester at the same time that maternal plasma triacylglycerol (TAG) increases. We conducted a pilot cross-sectional analysis of maternal plasma lipid status and birth weight in healthy, non-pregnant, primigravida Trinidadian women. Non-pregnant and pregnant women, in their second and third trimesters, and at term, were recruited at random from an antenatal clinic. Adult and umbilical cord plasma TAG, non-esterified fatty acids (NEFA) and phosphatidylcholine (PC) concentrations were determined from gas chromatographic analysis of fatty acids. Maternal height, weight, skinfold thickness and infant birth weight were measured. The infants born to Afro-Trinidadian and Indo-Trinidadian women were of low to normal birth weight (medians 3.07 and 3.22 kg, respectively). At term, plasma TAG concentration was approximately two fold (p < 0.05) greater than for non-pregnant women. The increment between 30-34 weeks was 1.5 to 1.9 fold lower than reported in other populations. There was a strong relationship (r = 0.8771, p = 0.019) between maternal and cord plasma TAG and NEFA, but not PC concentrations. There was no significant relationship between maternal TAG concentration at term and birth weight. The result suggests an impaired ability to increase plasma TAG concentrations during late gestation.