Socio-economic differences in height and body mass index of children and adults living in urban areas of Karachi, Pakistan.

OBJECTIVE: To study the socio-economic differences in height and body mass index (BMI) in urban areas of Karachi.
DESIGN: A comparative study was undertaken to compare the heights and BMIs of adults and children belonging to three distinctively different income groups living in urban areas of Karachi.
SETTING: Data was collected from families living in small, medium and large houses located in the authorised urban residential areas of Karachi.
SUBJECTS: A total of 600 families, 200 from each income group, were included in the study. Anthropometric measurements of 1296 females and 1197 males of different ages were taken.
METHODS: All the housewives were interviewed to collect socio-demographic information. Height and weight of all the available family members were measured. In order to determine the socio-economic difference in height status, the mean height in cm of adults was compared. For children (2-17 y) means of height-for-age Z-scores determined on the basis of NCHS reference values were compared. For studying the weight status the BMI of all the respondents was calculated and they were grouped into categories of under-, normal or overweight according to the NCHS recommended cut-off points. For adult men and women BMI values <18.5 kg/m(2) indicated underweight and >25 kg/m(2) indicated overweight. Among children, those having BMI values below the 5th percentile of the NHANES III reference values were categorised as underweight and those above the 95th percentile were termed overweight.
RESULTS: Height status improved with income level among adults and children of both sexes. Among males the difference in weight status was significant only among 2 to 18-y-olds (P<0.05 in each case). The rate of overweight among 2 to 18-y-old males was significantly higher (P=0.004) at the middle-income level (15%) as compared to low or high income. The rate of underweight was significantly higher (P=0.025) at the low-income level among 2 to 18-y-old males (31%, 21% and 22% at low-, middle- and high-income levels, respectively). Among females, rates of underweight were not significantly different at any age. Rates of overweight increased significantly (P=0.048) with income level among 41 to 60-y-old women (38%, 53% and 60% at low-, middle- and high-income levels, respectively).
CONCLUSION: Chronic undernutrition as indicated by deficit in height decreased with increasing income level. Socio-economic differences in weight status were not uniform among various age-sex groups. The influence of increasing affluence is likely to be seen both in the form of increased obesity among older females and underweight among children. Differing patterns of association between income and weight status among male and female children need to studied further with more accurate birth records, so as to further clarify the situation. In terms of prevention of nutrition-related disorders both problems of under- and over-nutrition need to be addressed.