Determinants of work capacity (predicted VO_2max) in non-pregnant women of reproductive age living in rural India

Background: The negative impact of anemia on work capacity has been studied extensively in male and female workers; however, the simultaneous contributions of confounding variables such as physical activity, as well as other behavioral and sociodemographic characteristics have not been considered. The purpose of this study was to examine cross-sectionally the multivariable correlates of work capacity in non-pregnant women (n = 330) living in rural India. Methods: The Reduction in Anemia through Normative Innovations (RANI) Project is a norms-based, clustered randomized controlled trial to reduce anemia among women (15–49 years) living in Odisha, India between 2018 and 2021. For the larger trial, 89 clusters of villages were randomized into treatment and control groups on a 1:1 basis. Women (2055/group) living in 15 selected clusters (40–41 villages) were then randomly selected for data collection. The sampling design also randomly-generated a subset (n = 375) of non-pregnant participants who performed a modified Queen’s College Step Test (QCST) and who wore an activity monitor for 3 days. Predicted work capacity (VO_2max) was determined using the QCST. Levels (h/day) of daily reclining, sitting, standing, walking (steps/day), and energy expenditure (MET∙h/day) were determined using an ActivPAL accelerometer. Hemoglobin concentrations (g/dL) were determined using a HemoCue photometer. Predetermined hierarchical (non-multilevel) regression models tested the independent associations between the primary study variables of interest (physical activity, hemoglobin concentrations) and predicted VO_2max, while adjusting for age, body mass index (BMI: kg/m²), education, parity, and dietary diversity score. Results: Approximately 61% of the participants had anemia (Hb < 12 g/dL). Age² (β = − 0.01; 95% CI: − 0.01, 0.00), BMI (β = − 0.19; 95% CI:-0.28, − 0.09), educational attainment (β = − 1.35; 95% CI: − 2.34, − 0.36), and MET∙h/day (β = 0.19; 95% CI: 0.00, 0.38) were significant and independent determinants of work capacity. Hemoglobin concentration was marginally associated with work capacity in the presence of the other covariables (β = 0.22; 95% CI:-0.02, 0.47). Conclusions: Our data indicate that factors other than anemia are important correlates of work capacity and should be considered when promoting the health and economic capacity of rural Indian women. Trial registration: Clinical Trial Registry- India (CTRI) http://ctri.nic.in/Clinicaltrials/pmaindet2.php?trialid=26285&EncHid=&userName=CTRI/2018/10/016186 on 29 October 2018.