Appendix K

Interview Processes Used in National Surveys

NHANES

In National Health and Nutrition Examination Survey (NHANES), anthropometric measurements are collected by trained health technicians during the health examination in the mobile examination clinic (MEC), using standardized procedures (CDC, 2011). In the health examination, measured height and weight are recorded and are used to calculate body mass index (BMI) defined as the weight in kilograms divided by the square of the height in meters. BMI is used to categorize weight status in adults (≥ 19 years) and children (< 19 years).

For children, BMI percentiles are used to classify underweight (< 5th), healthy (5 to ≤ 85th), overweight (85th to ≤ 95th), and obese (> 95th). For adults, percentiles are not used, and BMI is used to define underweight (< 18.5), normal weight (≥ 18.5 and ≤ 25), overweight (> 25 and ≤ 30) and obese (> 30). Obesity is further categorized into classes: class I (30 to < 35), class II (35 to < 40), and class III (≥ 40) (CDC, 2011).

Waist circumference is measured in a standing position, directly above the iliac crest, and recorded to the nearest millimeter, using a steel measuring tape. Precisely, participants are instructed by the technician to cross their arms and place their hands on their opposite shoulders. The technician then locates and marks the uppermost lateral border of the right ilium at the midaxillary line and measures the waist circumference. The technician places the measuring tape at the marking on the midaxillary line and wraps it around the waist, making sure that the tape is aligned horizontally. This is done by double-checking that it is parallel to the floor

and does not compress the waist or abdomen; the technician then records the measurement to the nearest millimeter (CDC, 2011).

Sagittal abdominal diameter (SAD) is measured in the supine position on the MEC examination table; trained NHANES technicians use an abdominal caliper to determine the external distance from the front of the abdomen to the small of the participant’s back at the iliac level line. More specifically, the participant is first positioned on the table with their knees bent, feet resting flat on the examination table, and arms crossed at the chest. The technician then locates the right iliac crest and marks the point at which it intersects with the midaxillary line, and then completes the same steps for the left iliac crest. After doing so, the iliac level line is able to be identified and marked in preparation for SAD measurement. The technician completes a minimum of two SAD measurements using an appropriately sized abdominal caliper. To complete a measurement, the technician asks the participant to raise his or her hips so the technician can insert the lower arm of the caliper under the small of the participant’s back. The technician checks to ensure that the lower arm of the caliper contacts the small of the participant’s back, grasps the caliper shaft with one hand, and slides the upper arm of the caliper down to ~2 centimeters above the abdomen with the other hand, making sure that the edge of the caliper is aligned with the mark at the iliac level line (CDC, 2011).

As outlined in the NHANES procedures manual (CDC, 2011), the participant is instructed by the technician to “slowly take in a gentle breath, slowly let the air out, and then pause” so the technician can slowly lower the upper arm of the caliper down onto the abdomen without compressing it and take the SAD measurement while the participant is in a resting state. The same process is repeated for any additional SAD measurements.

The dietary data collected in NHANES is provided as the U.S. Department of Agriculture (USDA) What We Eat in America survey. A 24-hour recall (24HR) is collected, first in-person in a MEC and then over the phone, approximately 3–10 days later, with trained interviewers using the Automated Multiple-Pass Method (AMPM; Blanton et al., 2006; Moshfegh et al., 2008). Participants are asked to report all foods and beverages consumed over the previous 24 hours (i.e., midnight to midnight the previous day) using the AMPM five-step process. The 24HRs are completed by the participant or their proxy, according to the age of the participant, in the following manner: children 2 to 5 years have a proxy; children 6 to 8 years have a proxy and provide assistance; children 9 to 11 years complete the 24HR with proxy assistance; and children and adults ≥12 years complete the 24HR individually. All recorded foods, beverages, and other food components are then converted to their energy value using the USDA Food and Nutrient Database for Dietary Studies (USDA, 2019).

Canadian Health Measures Survey-Nutrition

In the Canadian Health Measures Survey (CHMS) participants are first asked to complete the height (standing and sitting) and weight measurements using a Proscale 200 stadiometer (Accurate Technology Inc., Fletcher, NC), custom-built sitting height block with stadiometer, and Mettler Toledo scale with Panther Plus digit readout (Mettler Toledo Canada, Mississauga, ON), respectively. For height, participants remove their shoes, stand with their feet together, and keep the back side of their body in contact with the stadiometer as they look straight ahead and stand as “tall as possible.” Participants are then asked to “take a deep breath in and hold it” while the trained technician records the standing height in both centimeters and millimeters. For anthropometry, physical measurements include height (sitting and standing), weight, waist circumference, hip circumference, as well as skinfold thickness at five different sites (i.e., triceps, biceps, subscapular, iliac crest, and calf) (Bryan et al., 2007; Tremblay et al., 2007). Apart from hip circumference, all anthropometric measurements are collected in accordance with the Canadian Physical Activity, Fitness, and Lifestyle Approach Manual (Canadian Society for Exercise Physiology, 2003). For hip circumference, measurements are taken based on the Canadian Standardized Test of Fitness (CSTF, 1986). Weight status categories for children and adults are categorized as described above using the same classifications as NHANES.

Canadian Community Health Survey

In the 2015 CCHS-Nutrition, a household member is randomly selected and asked to complete a questionnaire on the demographics, health status, and lifestyle of the household, as well as a 24HR on either a weekend day or weekday to assess the dietary intakes of the selected individual over the previous 24 hours (Health Canada, 2017). During the 24 hours, participants are asked to provide detailed information on all foods consumed, including the type, time, and location of the eating occasion, as well as the weight or size of the portion consumed.

The 24HR is computer assisted and administered by trained interviewers in the home, using a Canadian modification of the USDA’s AMPM (Blanton et al., 2006). Depending on the age of the participant, some 24HRs are completed via proxy or are proxy-assisted. For example for children 1 to 5 years, the 24HR is completed by a parent or guardian proxy; for children 6 to 11 years, the 24HR is completed by the respondent, but is proxy-assisted by a parent or guardian; and for children and adults 12 years and older, the 24HR is completed by the respondent (Blanton et al., 2006).

Energy and nutrient values derived from food and beverage intake are calculated using Health Canada’s Canadian Nutrient File (version 2015) (Health Canada, 2021). In the most recent survey, approximately 20,487 CCHS-Nutrition participants completed the initial in-person 24HR in the 2015 cycle; an additional 35 percent of the main sample were randomly selected to complete a second dietary recall via telephone approximately 3 to 10 days after completion of the initial recall on a different day of the week. Participants were provided with a Food Model Booklet to help facilitate food recall and portion size estimation during the second 24HR. The response rates for the two 24HRs were 61.6 percent and 68.6 percent, respectively (Health Canada, 2017).

REFERENCES