2019 Data Collection Methods

Study population

Data collection occurred during June – August of 2019 and 2012 in the Mustang District of Nepal on the Tibetan Plateau’s southern reaches.  Villages of residence range in altitude from 3500 to 4200 m (11,550–13 860′). The study population consists of Nepal citizens who self-identify as ethnically Tibetan: they speak Tibetan dialects, share economic, religious and sociocultural practices common among highland Tibetans (Cho et al., 2017).

Study sample

The researchers invited 421 women who participated in a 2012 study in Upper Mustang District, Nepal, to join a follow-up study in 2019  (Childs, Craig et al. 2014, Craig, Childs et al. 2016, Cho, Basnyat et al. 2017, Jeong, Witonsky et al. 2018).  Data collection in 2019 centered on temporary laboratories established sequentially in the three largest area villages: Lo Monthang (3800m (Barigo E7, BARIGO Barometerfabrik GmbH, Baden-Württemberg, Germany; Latitude, Longitude 29º10’N, 83º57’E, Garmin eTrex HC series, Garmin International Inc., Olathe, KS), Tsarang (3500m; Latitude, Longitude 29º5’N, 83º56’E) and Ghami (3500m; Latitude, Longitude 29º3’N, 89º53’E).

Local elected officials and other community leaders, including women’s groups, approved the study and co-hosted recruitment meetings in these locations and other villages within a two-hour radius by foot or jeep.  We invited interested women to remain after these meetings and determine their eligibility to participate again. Other participants volunteered at the temporary laboratories.

Identification confirmation involved matching a woman’s name, residence village, animal year of birth, husband’s name (if any) in 2012, and the names and animal years of birth of the oldest and youngest living children in 2012.  Tibetans use a 12-year animal cycle to reckon ages.  An individual is one at birth and becomes two in the succeeding animal year.  Individuals know their animal years of birth and provide that along with age in years that is one year older than age reckoned in the Western system (Cynthia M Beall, 1981).  They rarely misstate their animal years, while age in years may be accurate within several years.  This study converted animal years of birth to Western age.

Data collection

The research team included U.S. – based researchers, ethnic Tibetan female nurses and research assistants, including a community member from each village with a temporary laboratory.  Upon confirming eligibility to participate, research assistants used established methods to interview each woman (C. M. Beall & Leslie, 2014) in the local dialect of Tibetan to update her reproductive history.

Measurements occurred indoors.  We had little control over the ambient indoor environment, apart from blocking the wind.  A box held over the hand shielded the sensor from bright sunlight streaming through the windows.  Temperature, barometric pressure, and relative humidity varied with the weather and altitude.  The barometric pressure between 6 and 7 am averaged 481, 494, and 497 mmHg at Lo Monthang, Tsarang, and Ghami, respectively.  Outdoor temperature averaged 13.3, 16.1 and 18.9 ºC (56, 61, and 66 ºF) and relative humidity averaged 61, 58, and 48% at the same time.   Indoor temperature, barometric pressure and relative humidity measured throughout the days of data collection varied widely (Figure 1).

Figure 1

credit: Keaton Markey

Height in centimeters without shoes, weight in kgs corrected for clothing, and calculated body mass index (BMI, kg/m^2) quantified body size.  Forced expiratory volume at six seconds (FEV6) measured lung volume.  Forced expiratory volume at one second (FEV1) measured airway caliber (Piko6, Ferraris, CO).  FEV6 and FEV1 are reported in BTPS.  The ratio of FEV1/FEV6 quantified their relative proportions.  Each woman performed three acceptable maximal inspiration maneuvers and a forced fast expiration measured over six seconds. We chose FEV6 rather than its equivalent forced vital capacity (FVC) because it is explicitly defined, avoids variation in expiration time, and is easier to understand and perform (22).  Percent of oxygen saturation of hemoglobin, hemoglobin concentration, and pulse were measured noninvasively with the Masimo Pronto 7® using a described protocol (18, 23). Twenty-one women provided second measurements on another day for evaluating replicability

Noninvasive observations of hemoglobin concentration, percent of oxygen saturation of hemoglobin, and pulse using the Masimo Pronto-7 ® and a protocol described previously (Cho et al., 2017).  Women washed their hands, removed nail polish, and then sat comfortably with one arm resting on a flat surface at about heart height, hand lying upon a reusable hand warmer to ensure adequate perfusion.  They remained seated for about ten minutes before the measurements took place.  A sensor placed on the forefinger obtained stable readings within a minute and then displayed and saved a single value for each trait.  The Pronto-7 ® shows the pulse wave graphically and shuts off automatically upon detecting excessive motion.  The Pronto-7 ® measures the percent of oxygen saturation of hemoglobin with an accuracy of 2% and a resolution of 1%;  pulse with an accuracy of 3 beats/minute and a resolution of one bpm, and hemoglobin concentration with an accuracy of 1.0 gm/dL and a resolution of 0.1 gm/dL under usual laboratory conditions (Masimo Corporation, 2015).

Collecting Biological Data: Hypoxic Ventilatory Response

References

Beall, C. M. (1981). Growth in a population of Tibetan origin at high altitude. Human Biology, 8(1), 31–38. DOI.

Beall, C. M., & Leslie, P. W. (2014). Collecting women’s reproductive histories. American Journal of Human Biology, 26(5), 577–589. DOI.

Childs, G., Craig, S., Beall, C. M., & Basnyat, B. (2014). Depopulating the Himalayan highlands: Education and outmigration from ethnically Tibetan communities of Nepal. Mountain Research and Development, 34(2), 85–94. DOI.

Cho, J. I., Basnyat, B., Jeong, C., Di Rienzo, A., Childs, G., Craig, S. R., Sun, J., & Beall, C. M. (2017). Ethnically Tibetan women in Nepal with low hemoglobin concentration have better reproductive outcomes. Evolution Medicine and Public Health, 2017(1), 82–96. DOI.

Craig, S. R., Childs, G., & Beall, C. M. (2016). Closing the womb door: Contraception use and fertility transition among culturally Tibetan women in Highland Nepal. Maternal and Child Health Journal, 20(12), 2437–2450. DOI.

Jeong, C., Witonsky, D. B., Basnyat, B., Neupane, M., Beall, C. M., Childs, G., Craig, S. R., Novembre, J., & Di Rienzo, A. (2018). Detecting past and ongoing natural selection among ethnically Tibetan women at high altitude in Nepal. PLoS Genetics, 14(9), e1007650. DOI.

Masimo Corporation. (2015). Pronto-7 spot check pulse CO-oximeter operator’s manual. Masimo Corporation.