Question

The purpose of this study was to
assess the vitamin D status of pregnant women residing in Beijing in winter and evaluate the
impact of maternal factors on serum 25hydroxyvitamin
D [25(OH)D] levels. The study was
conducted on 125 healthy pregnant women. For each individual, data concerning prepregnancy
weight, educational status, use of multivitamins and behavioral factors such as daily duration of
computer use, walking and sun exposure were obtained. Serum concentrations of 25(OH)D were
measured by enzymelinked
immunosorbent assay. The prevalence of vitamin D deficiency
(25(OH)D < 50 nmol/L) was 96.8% and almost half (44.8%) of women were severely vitamin D

deficiency (25(OH)D < 25 nmol/L). The concentration of 25(OH)D was lower in women with
shorter duration of sun exposure (≤ 0.5 h/day, 25.3 ± 8.9 nmol/L) than that in women with
longer duration of sun exposure (> 0.5 h/day; 30.3± 9.5 nmol/L; P = 0.003). Thirtysix
women
(28.8%) had sun exposure duration ≥ 1.5h/day. The 25(OH)D concentration in these women
was 31.5 ± 9.4 nmol/L which was also much lower than the normal level. Women who reported
taking a multivitamin supplement had significantly higher 25(OH)D concentrations (32.3 ± 9.5
nmol/L) when compared with nonusers
(24.9 ± 8.2 nmol/L; P < 0.001). Pregnant women in
Beijing are at very high risk of vitamin D deficiency in winter. Duration of sun exposure and the
use of multivitamin were the most important determinants for vitamin D status.

Which type of epidemiologic study design is described?

Answer 1

1 This is an cohort design

Study designs are classified as Observational and Experimental studies.In Observational studies the researcher observes and systematically collects information ,and does not try to change the people being observed.Observational designs are classified as Cross-sectional surveys,Cohort studies and Cross-control studies.In this design one or more samples are followed prospectively and subsequent status evaluations with respect to a disease or outcome are conducted to determine which initial participants exposure characteristics are associated with it.As the study is conducted,outcome from participants in each cohort is measured and relationships with specific characteristics determined.Subjects in cohorts can be matched,standardization of criteria is possible and easier and cheaper than a randomized control trial