K. Nawata, M. Kimura
512 minutes or more twice or more in a week for more than a year; 0 otherwise,
Daily_activity 1: doing physical activities walking or equivalent for one hour or more daily, 0: otherwise, Walk_fast 1: walking faster than other people of a
similar age and the same gender; 0: otherwise, Smoke 1: smoking; 0: otherwise, Alcohol_freq 0: not drinking alcoholic drinks, 1: some-times, 2: everyday, Al-
cohol_amount 0: not drinking; 1: drinking less than 180 ml of Japanese sake wine about a 15 alcohol percentage or equivalent alcohol in a day when drinking;
2: drinking 180 - 360 ml; 3: drinking 360 - 540 ml; 4: drinking 540 ml or more, Sleep 1: sleeping well; 0: otherwise, and Trend, which is the time trend by year
and given by year of checkup 2013. The results of 11,850 checkups without missing values for any of the explana-
tory variables were used in this model. The mean and SD of the dependent vari- able Diff_SBP were 5.6 and 9.6 mmHg. The mean and SD of First_SBP were
138.0 and 19.1 mmHg in this case. Female, Age and Height are basic characteris- tics of individuals, and 17.8 were female, means were 50.2 and 167.9 cm and
SD are 7.2 and 7.7 cm for Age and Height, respectively. BMI and Anamnesis represented the current obesity and health conditions with mean and SD of 24.3
and 3.96 for BMI, and 53.7 having an anamnesis. Eat_fast, Supper_time, Af- ter_supper and No_breakfast
are variables regarding eating habits, and 34.4, 42.8, 12.1 and 23.5 answered “yes” for these variables, respectively. Exer-
cise, Daily_activity and Walk_fast represent exercise and physical abilities, and 16.7, 25.6 and 38.3 answered 1 for these variables. For Smoke, 38.9 were
smokers. Alcohol_freq and Alcohol_amount represent alcohol consumption; 34.9, 23.9 and 41.2 answered 0, 1 and 2 for Alcohol_freq, and 34.9.
21.1, 29.5, 12.2 and 2.4 answered 0, 1, 2, 3 and 4 for Alcohol_amount, respectively. For Sleep, 61.3 answered “sleeping well”.
The result of estimation is given in Table 2
. As the previous model, the esti- mate of First_SBP is highly significant and t-value is 52.16. The estimated value
is 0.235 which is very close to that of Model 1A 0.224. This means that a simi- lar relation holds for these variables even if the various factors of individuals are
considered. The estimates of Age, BMI, Alcofol_freq and Alcohol_amount are negative significant at the 1 Age and BMI and 5 Alcofol_freq and Alco-
hol_amount. These variables make the difference smaller. One the other hand, the estimates of Female and Daily_activity are positive and significant at the 1
level and these variables make the difference larger. Other variables were not significant at the 5 level.
Figure 6 is a graph of residuals calculated from Model
1B. The distribution is almost symmetric and systematic skewness was elimi- nated in this model.
3.2. Difference of DBP
Figure 7 shows the relation of the first measurement and difference for DBP. Like
the SBP case, there exists a positive correlation between the two variables and the correlation coefficient is 0.365. The gross relation of the first measurement is
given by the model.
K. Nawata, M. Kimura
513 Table 2.
Results of estimation for difference of SBP measurements Model 1B.
Variable Estimate
SE t-value
Constant −15.6414
2.7025 −5.7878
First_SBP 0.2347
0.0045 52.1630
Age −0.1203
0.0121 −9.9212
Female 1.2488
0.2971 4.2034
Height −0.006095
0.014152 −0.4307
BMI −0.1614
0.0224 −7.2142
Anamnesis −0.0642
0.1622 −0.3958
Eat_fast 0.0658
0.1736 0.3789
Late_Supper 0.0599
0.1699 0.3526
After_Supper 0.0026
0.2463 0.0106
No_Breakfas 0.0010
0.1948 0.0054
Exercise 0.3312
0.2277 1.4544
Daily_activity 0.6465
0.1945 3.3241
Walk_fast 0.1598
0.1705 0.9372
Smoke −0.1556
0.1723 −0.9031
Alcofol_freq −0.3043
0.1475 −2.0639
Alcohol_amount −0.2271
0.1107 −2.0520
Sleep 0.0269
0.1657 0.1626
Trend −0.0444
0.0942 −0.4709
R
2
0.193 ˆ
σ 8.613
SE: standard error, : significant at the 5 level, : significant at the 1 level.
Figure 6. Distribution of residuals in Model 1B.
Figure 7. Relation of the first measurement and difference DBP.
K. Nawata, M. Kimura
514 Model 2A:
Diff_SBP -12.29 0.1694First_SBP u
= +
+
,
R
2
= 0.1320, ˆ
σ
= 5.479. 4 0.2862 0.00326
where Diff_DBP is the difference between the first and second DBP measure- ments and First_DBP is the first DBP measurement. Next, we consider the fol-
lowing model that contains variables that may affect Diff_DBP, Model 2B:
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
17
Female Eat_fast
Late_Supper After_Supper
No_Breakfast Ex
Diff_DBP First_DBP
Age Height
BMI Ana
ercise Daily_activity
Walk_fast Smo
mn ke
Alcofo esis
l_freq Alcoh
β β β
β β
β β
β β
β β
β β
β β
β β
= +
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+
18 19
ol_amount Sleep
Trend .
u β
β +
+ +
5
The explanatory variables other than First_DBP were the same as in the case of SBP Model 1B. The result of estimation is given in
Table 3 . The estimate of
First_DBP is 0.1766 and similar to the result of Model 2A and the relation be- tween Diff_DBP and First_DBP does not change much even if we consider var-
ious characteristics of individuals. The estimates of Age, BMI, No_Breackfast, Alcohol_amount
,
and Sleep are negative and significant at the 1 BMI and Al- cohol_amount and 5 other variables. On their hand, the estimate of Female,
Table 3. Results of estimation for difference of DBP measurements Model 2B.
Variable Estimate
SE t-value
Constant −8.7721
1.6985 −5.164
First_DBP 0.1766
0.0042 42.2593
Age −0.0157
0.0075 −2.1009
Female 0.9135
0.1870 4.8864
Height −0.009699
0.008906 −1.0890
BMI −0.0633
0.0140 −4.5194
Anamnesis −0.1085
0.1020 −1.0636
Eat_fast −0.0146
0.1092 −0.1337
Late_Supper −0.0051
0.1069 −0.0476
After_Supper −0.0287
0.1550 −0.1850
No_Breakfast −0.2570
0.1226 −2.0961
Exercise 0.2777
0.1434 1.9373
Daily_activity 0.0181
0.1224 0.1478
Walk_fast 0.0317
0.1073 0.2954
Smoke 0.0955
0.1085 0.8796
Alcofol_freq −0.0619
0.0929 −0.6661
Alcohol_amount −0.2112
0.0697 −3.0313
Sleep −0.2062
0.1041 −1.9814
Trend 0.0416
0.0592 0.7026
R
2
0.134 ˆ
σ 5.419
SE: standard error, : significant at the 5 level, : significant at the 1 level.
K. Nawata, M. Kimura
515 Daily_activity are positive at the 1 level. The estimates of Age, Female, BMI
and Alcohol_amount are significant for both SBP and DBP and these variables are considered as important variables affecting the BP measurements.
4. Discussion
