DXA-Measured Body Composition Modifies Temperature–Blood Pressure Associations by Sex in Johannesburg, South Africa
1
Planetary Health Research, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
2
SAMRC/Wits Developmental Pathways for Health Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
3
Biomedical Research and Innovation Platform, South African Medical Research Council, Cape Town, South Africa
4
Climate System Analysis Group, Department of Environmental and Geographical Science, University of Cape Town, Cape Town, South Africa
Popul. Med. 2026;8(Supplement Supplement 1):A450
ABSTRACT
BACKGROUND:
Rising urban temperatures in sub-Saharan Africa¹ intersect with high burdens of obesity and hypertension², yet how body composition influences cardiovascular responses to heat is poorly understood. Central adiposity may impair heat dissipation through reduced skin blood flow. Using dual-energy X-ray absorptiometry (DXA), we examined whether total body fat and android fat modify associations between ambient temperature and blood pressure or glucose, stratified by sex.
METHODS:
Cross-sectional data from the Middle-aged Soweto Cohort (MASC) study (2017–2018, Johannesburg) were linked to ERA5 reanalysis climate data. Adults with complete DXA data were included (males N=467; females N=457; age 41–71 years). Outcomes were systolic blood pressure (SBP), diastolic blood pressure (DBP), and fasting glucose. Outcome-specific temperature lags were evaluated (1-day for blood pressure; 7-day for glucose). Sex-stratified linear regression models tested independent effects of body composition, temperature–adiposity interactions, and temperature associations by android fat level.
RESULTS:
Higher android fat was independently associated with higher SBP in males (+3.4 mmHg per 1%; 95% CI: 2.3, 4.5; p<0.001), higher DBP (males: +1.7 mmHg, p<0.001; females: +1.2 mmHg, p=0.002), and higher fasting glucose in both sexes (males: +0.20 mmol/L, p<0.001; females: +0.28 mmol/L, p<0.001), independent of BMI. Significant temperature–adiposity interactions were observed for DBP: higher total body fat attenuated the temperature–DBP association in males (interaction p=0.048), while higher android fat amplified this association in females (interaction p=0.028). In females, inverse temperature–blood pressure associations were observed only at the highest levels of android fat (SBP: −6.0 mmHg per 5°C, p=0.008; DBP: −3.8 mmHg, p=0.002), with no associations at lower levels.
CONCLUSIONS:
DXA-measured android adiposity is independently associated with higher blood pressure and fasting glucose and modifies temperature–blood pressure relationships in a sex-specific manner. In women, high android adiposity identifies a subgroup with heightened cardiovascular sensitivity to ambient temperature, supporting body composition–informed heat vulnerability assessment in urban populations.
Rising urban temperatures in sub-Saharan Africa¹ intersect with high burdens of obesity and hypertension², yet how body composition influences cardiovascular responses to heat is poorly understood. Central adiposity may impair heat dissipation through reduced skin blood flow. Using dual-energy X-ray absorptiometry (DXA), we examined whether total body fat and android fat modify associations between ambient temperature and blood pressure or glucose, stratified by sex.
METHODS:
Cross-sectional data from the Middle-aged Soweto Cohort (MASC) study (2017–2018, Johannesburg) were linked to ERA5 reanalysis climate data. Adults with complete DXA data were included (males N=467; females N=457; age 41–71 years). Outcomes were systolic blood pressure (SBP), diastolic blood pressure (DBP), and fasting glucose. Outcome-specific temperature lags were evaluated (1-day for blood pressure; 7-day for glucose). Sex-stratified linear regression models tested independent effects of body composition, temperature–adiposity interactions, and temperature associations by android fat level.
RESULTS:
Higher android fat was independently associated with higher SBP in males (+3.4 mmHg per 1%; 95% CI: 2.3, 4.5; p<0.001), higher DBP (males: +1.7 mmHg, p<0.001; females: +1.2 mmHg, p=0.002), and higher fasting glucose in both sexes (males: +0.20 mmol/L, p<0.001; females: +0.28 mmol/L, p<0.001), independent of BMI. Significant temperature–adiposity interactions were observed for DBP: higher total body fat attenuated the temperature–DBP association in males (interaction p=0.048), while higher android fat amplified this association in females (interaction p=0.028). In females, inverse temperature–blood pressure associations were observed only at the highest levels of android fat (SBP: −6.0 mmHg per 5°C, p=0.008; DBP: −3.8 mmHg, p=0.002), with no associations at lower levels.
CONCLUSIONS:
DXA-measured android adiposity is independently associated with higher blood pressure and fasting glucose and modifies temperature–blood pressure relationships in a sex-specific manner. In women, high android adiposity identifies a subgroup with heightened cardiovascular sensitivity to ambient temperature, supporting body composition–informed heat vulnerability assessment in urban populations.
| eISSN: | 2654-1459 |
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