Table 1.

Distribution of Demographic, Health, and Environmental Factors Among Participants With Heart Rate Variability Measured Between November 2000 and December 2008, Normative Aging Study, Boston, Massachusetts

Variable	First Study Visit (n = 694)			All Study Visits (n = 1,353)
	Mean (SD)	No. of Participants	%	Mean (SD)	No. of Participants	%
Age, years	73.26 (6.68)			74.71 (6.67)
Body mass indexa	28.20 (4.11)			28.11 (4.24)
Mean arterial pressure, mm Hg	92.73 (10.67)			89.88 (10.9)
Fasting blood glucose concentration, mg/dL	107.16 (26.49)			106.56 (23.41)
Season
Spring		172	24.78		331	24.46
Summer		166	23.92		335	24.76
Fall		212	30.55		417	30.82
Winter		144	20.75		270	19.96
Smoking status
Never smoker		200	28.82		407	30.08
Current smoker		31	4.47		46	3.40
Former smoker		463	66.71		900	66.52
Alcohol consumption of ≥2 drinks/day		130	18.98		243	18.08
Use of β-blockers		283	40.73		556	41.09
Use of calcium channel blockers		149	21.47		271	20.03
Use of angiotensin-converting enzyme inhibitors		202	29.11		419	30.97
Log10 SDNN, m/second2	1.59 (0.32)			1.59 (0.34)
Log10 high-frequency power, m/second2	2.08 (0.83)			2.12 (0.85)
Log10 low-frequency power, m/second2	2.10 (0.65)			2.10 (0.69)
Relative humidity, %	67.9 (15.5)			66.9 (15.3)
Examination room temperature, °C	24.23 (1.79)			23.87 (1.62)
48-hour moving average of PM2.5, μg/m3	16.89 (10.54)			13.32 (7.21)
4-hour moving average of ozone, ppb	18.26 (11.54)			15.39 (9.73)
1-hour maximal temperature, °C	15.46 (10.56)			15.27 (10.56)
Daily mean temperature, °C	11.18 (9.74)			11.13 (9.77)
1-hour maximal apparent temperature, °C	16.03 (9.62)			15.90 (9.65)
Daily apparent temperature, °C	11.98 (8.83)			11.94 (8.88)

Abbreviations: PM_2.5, particulate matter ≤2.5 μm in aerodynamic diameter; SD, standard deviation; SDNN, standard deviation of normal-to-normal beat intervals.

^aWeight (kg)/height (m)².