We will analyze possible effects both from a cross-sectional (i.e. different age groups at single time-points) and from a lifetime perspective (i.e. following an age-cohort of insured over time).
The majority of studies were cross-sectional, i.e. exposures and HIV status had been determined at the same time.
These limitations are unavoidable for cross-sectional (i.e., single time point) study designs of dental caries.
Crude and adjusted ORs (95% CIs) of overall preterm birth in association with averaged and cross-sectional (i.e., by visit) urinary BPA levels are presented in Table 3. Adjusted models controlled for maternal age, maternal race/ethnicity, educational level attained, medical insurance, parity, prior history of preterm birth, and BMI.
Children with low parasite densities at cross sectional survey (i.e. lower geometric mean densities over time) had a lower incidence of clinical malaria compared to those with higher densities, suggesting that 'resting' levels of asymptomatic parasitaemia may reflect the immune status of the individual.
Generalization of the findings presented should be made with caution because of the following limitations: this study shared the limitations of other cross sectional studies, i.e. the difficulty of determining causal relationship between variables.
Figure 4(a) demonstrates the typical cross sectional images (i.e., the B-frame images in the fast axis) captured at the location marked by the red line in Fig. 4 d).
The cross-sectional area was calculated assuming an elliptic cross-sectional area, i.e., equal to πab, where a and b are equal one-half tendon height and width, respectively.
It should be noted that the inductance was estimated by assuming that the rectangular cross-section coil was given the same inductance as a circular cross-section coil of the same cross-sectional area (i.e., l × w ≅ π r); in practice, the two are not very different, although the method by Kostic would be more reliable.
