TABLE 1.
Baseline characteristics of the study group (n = 331), by obese status.
| Variable | Obese (n = 73) | Non-obese (n = 258) | P |
| Age (years) | 70.3 ± 6.8 | 69.2 ± 7.2 | 0.31 |
| Sex (n, % women) | 42, 58% | 158, 61% | 0.57 |
| Education (years) | 16.2 ± 2.6 | 17.0 ± 2.2 | 0.02 |
| BMI | 34.4 ± 3.9 | 24.4 ± 2.8 | NA |
| SBP (mmHg)a | 131.8 ± 16.7 | 122.6 ± 15.7 | <0.001 |
| DBP (mmHg)a | 78.1 ± 10.4 | 72.7 ± 10.1 | <0.001 |
| Glucoseb (mg/dL) | 89.4 ± 17.2 | 82.8 ± 16.1 | 0.001 |
| QUICKIc | 0.35 ± 0.04 | 0.38 ± 0.04 | <0.001 |
| Insulin resistancec (n, %) | 35, 58% | 37, 17% | <0.001 |
| Diabetes mellitus (n, %) | 6, 8% | 11, 4% | 0.18 |
| Antihypertensive medication (n, %) | 32, 44% | 80, 31% | 0.04 |
| Statins (n, %) | 27, 37% | 83, 32% | 0.44 |
| Hippocampal volumee (% ICV) | 0.261 ± 0.003 | 0.260 ± 0.002 | 0.76 |
| Gray matter volumee (% ICV) | 39.6 ± 0.41 | 41.3 ± 0.21 | <0.001 |
| Hippocampal CBFf (ml/100 g/min) | 63.2 ± 1.03 | 64.1 ± 0.55 | 0.42 |
| Cortical CBFg (ml/100 g/min) | 58.5 ± 0.67 | 58.5 ± 0.35 | 0.99 |
| Hippocampal CVRCO2 (%)h | 0.70 ± 2.70 | 1.54 ± 2.33 | 0.01 |
| Cortical CVRCO2 (%)i | 0.81 ± 1.54 | 1.06 ± 1.42 | 0.18 |
| CO2 difference (mmHg) | 5.7 ± 4.0 | 6.2 ± 3.9 | 0.36 |
| SatO2 difference (%)j | −0.30 ± 1.7 | −0.48 ± 1.5 | 0.39 |
| Respiratory rate difference (breaths/min)k | −0.53 ± 3.0 | −0.50 ± 2.6 | 0.95 |
| Heart rate difference (beats/min)l | 0.34 ± 4.9 | 0.35 ± 3.1 | 0.98 |
BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; QUICKI, quantitative insulin sensitivity check index; ICV, intracranial volume; CBF, cerebral blood flow; CVRCO2, cerebrovascular reactivity to carbon dioxide; SatO2, oxygen saturation. Data are presented as mean ± standard deviation, p-values were obtained using the Mann-Whitney U-test, unless otherwise indicated. For categorical variables, χ2 was used.aData available for 328 subjects: 72 obese and 256 non-obese.bData available for 325 subjects: 71 obese and 254 non-obese.cData available for 280 subjects: 60 obese and 220 non-obese. Comparisons of brain volumes, CBF, and CVRCO2 were performed with ANCOVA with initial adjustments for age, sex, and hypertension. Covariates were retained in the model only if significant.eValues presented as mean ± SE, a p-value from ANCOVA after accounting for age and sex.fPresented as mean ± SE, a p-value from ANCOVA after accounting for sex.gPresented as mean ± SE, a p-value from ANCOVA after accounting for sex and hypertension.hData available for 298 subjects: 66 subjects with obesity and 232 non-obese subjects.iData available for 325 subjects: 73 subjects with obesity and 252 non-obese subjects.jData available for 310 subjects: 70 subjects with obesity and 240 non-obese subjects.kData available for 306 subjects: 69 subjects with obesity and 237 non-obese subjects.lData available for 308 subjects: 68 subjects with obesity and 240 non-obese subjects. Differences in CO2, SatO2, respiratory rate, and heart rate are between baseline and challenge conditions (rebreathing). p-values come from GML repeated measures analyses, with obesity status as the between-subjects factor; baseline and challenge vital signs values as the within-subjects factor. Significant p values were bold.