International Journal ofEnvironmental Researchand Public Health

ArticleSubjective Happiness, Frequency of Laughter, andHypertension: A Cross-Sectional Study Based on the Japan
Gerontological Evaluation Study (JAGES)
Fumikazu Hayashi 1,2, *,† , Yuka Shirai 1,† , Tetsuya Ohira 1,2 , Kokoro Shirai 3 , Naoki Kondo 4
and Katsunori Kondo 5,6
1

2

3
4
5

6

*
†

Citation: Hayashi, F.; Shirai, Y.;
Ohira, T.; Shirai, K.; Kondo, N.;
Kondo, K. Subjective Happiness,
Frequency of Laughter, andHypertension: A Cross-Sectional
Study Based on the Japan
Gerontological Evaluation Study(JAGES). Int. J. Environ. Res. Public
Health 2023, 20, 5713. https://doi.org/10.3390/ijerph20095713

Department of Epidemiology, Fukushima Medical University School of Medicine, 1 Hikariga-oka,
Fukushima 960-1295, Japan
Radiation Medical Science Center for the Fukushima Health Management Survey,
Fukushima Medical University, 1 Hikariga-oka, Fukushima 960-1295, Japan
Department of Public Health, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
Department of Social Epidemiology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
Department of Social Preventive Medical Sciences, Center for Preventive Medical Sciences, Chiba University,
Chiba 263-8522, Japan
Department of Gerontological Evaluation, Center for Gerontology and Social Science, National Center for
Geriatrics and Gerontology, Ohbu 474-8511, Japan
Correspondence: fhayashi@fmu.ac.jp; Tel.: +81-(24)-5471343
These authors contributed equally to the work.

Abstract: In recent years, positive psychological factors, such as subjective happiness and laughter,
have been reported to be associated with cardiovascular disease. In this study, we examined therelationship of hypertension with subjective happiness and frequency of laughter using the data fromthe Japan Gerontological Evaluation Study (JAGES). Of the 138,294 respondents, 26,368 responded
to a version of the self-administered questionnaire that included a question about the frequency oflaughter in the JAGES 2013. In total, 22,503 (10,571 men and 11,932 women) were included in theanalysis after excluding those with missing responses regarding a history of hypertension, frequencyof laughter, and subjective happiness. The prevalence of hypertension in this study was 10,364 (46.1%).
Multivariate logistic regression analysis showed that age, female sex, obesity, infrequent chewing,
former and current drinker, seeing three to five friends, and the absence of hobbies were positively
associated with hypertension. However, infrequent laughter/high level of subjective happiness,frequent laughter/high level of subjective happiness, being underweight, and current smoker were
negatively associated with hypertension. As per the findings of this study, it was determined that
subjective happiness was negatively associated with hypertension. Therefore, this study suggeststhat having more opportunities to feel happiness may be important in preventing hypertension.

Academic Editor: Paul B.
Tchounwou

Keywords: subjective happiness; laughter; hypertension; Japan; older adults

Received: 27 February 2023
Revised: 28 April 2023
Accepted: 30 April 2023
Published: 3 May 2023

Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms andconditions of the Creative Commons
Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

1. Introduction
Subjective happiness has been recognized as a factor that can positively impact the
cardiovascular system. In recent years, studies in Western countries have shown a reduced
incidence of cardiovascular disease and hypertension in individuals with higher levelsof subjective happiness and emotional vitality [1–3]. Additionally, some studies haveindicated that emotional vitality, positive emotions, and life purpose, which are considered
components of happiness, can lower the risk of stroke [4–6]. Hence, enhancing subjective
happiness could benefit the cardiovascular system and, in turn, improve overall health.
However, a report indicated that the correlation between happiness and chronic diseases,
including cerebral infarctions and heart attacks, is inconsistent and further investigation isnecessary [7].

Int. J. Environ. Res. Public Health 2023, 20, 5713. https://doi.org/10.3390/ijerph20095713

https://www.mdpi.com/journal/ijerph

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Recently, laughter has received attention as a factor with a positive effect on the
cardiovascular system. People with frequent laughter have been reported to have a lower
risk of cardiovascular disease [8,9]. A study using data from the Japan Gerontological
Evaluation Study (JAGES) 2013 found an association between the frequency of laughterand the prevalence of cardiovascular disease [10]. Other studies suggest that laughterinterventions may bring many health benefits, such as increased heart rate variability [11]and improved immune system [12,13], HbA1c [14], and vascular function [15,16]. Thesefindings suggest that having more opportunities for laughter in daily life may benefit the
cardiovascular system and contribute to improved health.
Previous studies examining the correlation between laughter and its health benefits
have predominantly focused on the following two types of laughter: spontaneous andintentional. Spontaneous laughter has positive effects, whereas intentional laughter—also
known as simulated laughter—is devoid of emotional components. Argyle hypothesizedthat positive emotions stemming from laughter may affect one’s health status [17]. Conversely, a laughter yoga intervention study utilizing simulated laughter reported thatlaughter had health benefits. Notably, it reduced depression scores and body mass index [18,19]. Therefore, whether positive emotions from laughter have health benefits
remains a point of contention.
A review of the psychological implications of laughter has shown that laughter promotes psychological wellness [20]. However, the impact of laughter frequency and thedifference in cardiovascular disease prevalence between patients with high and low subjective well-being remains unclear. Currently, no study has assessed the connection between
laughter and subjective happiness with cardiovascular disease. While subjective happinessis a psychological factor, laughter can occur without emotions and can be considered aseparate behavioral factor. Thus, this study aimed to examine the relationship between hypertension, which is considered to have a high prevalence among cardiovascular diseases,
and the frequency of laughter and subjective happiness, using data from the JAGES. In thecurrent study, individuals who frequently laugh and who have high levels of subjective
happiness were hypothesized to show a low prevalence of hypertension.
2. Materials and Methods
2.1. Study GroupA flow chart of this study is shown in Figure 1. The JAGES started in 2010 to create ascientific basis for preventive policies for a healthy and long life. The JAGES cohort was established in 2010 to investigate factors affecting the health of independent individuals over
65 in 30 municipalities in Japan. In 2013, the JAGES mailed questionnaires to 195,290 residents over 65: 138,294 responded (70.8%). The study used data from 26,368 respondents
who answered version B, which assessed oral hygiene, optimism, subjective health, andfrequency of laughter. Finally, 22,503 respondents (10,571 men and 11,932 women) were
included after excluding those missing information on hypertension, frequency of laughter,and subjective happiness. The study analyzed the association of hypertension with frequency of laughter and/or subjective happiness along with factors such as age, sex, height,
weight, caregiving, household income, number of teeth, chewing ability, drinking habits,
smoking habits, the Tokyo Metropolitan Institute of Gerontology Index of Competence(TMIG-IC), frequency of visiting friends, family relationships, work status, hobbies, andmarital status.
2.2. Definitions of Hypertension
Respondents who reported having hypertension as a current or past medical condition
were defined as having hypertension.

Int. J. Environ. Res. Public Health 2023, 20, 5713

3 of 12Figure 1. Flowchart of research subject selection.

2.3. Definitions of Laughter/Subjective Happiness
Laughter was measured on a 4-point scale, with “almost every day” being defined as“frequent laughter” and the other responses as “infrequent laughter”. Subjective happiness
was rated on a scale of 1 to 10, with scores ≥8 being defined as “high level of subjective
happiness” and scores <8 as “low level of subjective happiness”. The combination of laughter and subjective happiness was divided into four categories: “infrequent laughter/low
level of subjective happiness”, “frequent laughter/low level of subjective happiness”, “infrequent laughter/high level of subjective happiness”, and “frequent laughter/high levelof subjective happiness”.
2.4. Definitions for Obesity and Underweight
Body mass index (BMI) has been shown to be linked with clinic systolic and diastolicblood pressures [21]. According to the World Health Organization, obesity is defined as a
BMI of ≥30 kg/m2 [22]. However, only 2–3% of Japanese adults have a BMI ≥30 kg/m2 ,which is much lower than in Western countries [23]. In this study, BMI was calculated fromself-reported height and weight, and obesity was defined as a BMI ≥ 25 kg/m2 (per therecommendation of the Japan Society for the Study of Obesity) [24]. Underweight was
defined as a BMI < 18.5 kg/m2 .
2.5. Definition of Caregiving and Assistance Status
Tamada et al. reported that people who rarely laugh have a higher risk of death orneed for care than those who laugh daily [25]. Caregiving/assistance status was scoredusing a 3-point scale: “not needed”, “needed but not received”, and “received”.
2.6. Definition of Household Income
The Multi-centre National Population Health Examination Surveys (WOBASZ) study
in Poland found a correlation between household income and hypertension prevalence [26].
The household income was rated on a 15-point scale, with a range from JPY < 0.5 million to
JPY ≥ 12 million. Low income was defined as JPY < 2 million based on the 2014 National
Health and Nutrition Survey in Japan [27].

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4 of 122.7. Definitions Related to the Number of Teeth and Chewing Ability
Several studies have linked hypertension with periodontal disease [28]. The oral
environment is thus an important factor in hypertension studies. In this study, the numberof teeth was assessed using a 5-point scale: 0, 1–4, 5–9, 10–19, and ≥20. The report of the2013 National Health and Nutrition Examination Survey in Japan showed that a higher
percentage of people with ≥20 teeth can eat anything compared to those with <20 [29].
Thus, “≥20 teeth” and “<20 teeth” were compared. The hardness of food that could be
eaten was also scored on a 5-point scale: “anything”, “almost”, “limited”, “rarely chewing”,
and “liquid diet”.
2.8. Definition of Drinking and Smoking Habits
Heavy drinking and smoking positively impact blood pressure [30,31]. Drinking habitswere scored on a 3-point scale: “no drinker”, “former drinker”, and “current drinker”.
Smoking habits were also scored on a 3-point scale: “no smoker”, “former smoker”,
and “current smoker”.
2.9. Definition of TMIG-IC
Activities of daily living have been reported to be associated with hypertension [32].
The TMIG-IC was used to evaluate BADLs, such as walking, moving, eating, bathing,
toileting, and dressing [33]. A score of 11 in the 65–74 age group or ≥10 in the 75+ age
group was considered “good” BADL and a score below that was considered “poor” BADL.
2.10. Definitions Regarding Social Network
Kim et al. found a link between small social networks and metabolic syndrome [34].
A 6-pt scale measured frequency of seeing friends: “4+ times/week”, “2–3 times/week”,“once/week”, “1–3 times/month”, “a few times/year”, and “not seeing friends”. A 5pt scale measured number of friends met: “≥10”, “6–9”, “3–5”, “1–2”, and “0 (none)”.
A 3-point scale determined family living arrangement: “living alone”, “with family”, and“others”. Results were divided into “living alone” and “others”. Employment was determined using a 2-point scale: “employed” and “unemployed”. Hobbies reflect participationin self-centered social networks [35]. A 2-point scale determined hobby presence: “yes” or“no”. A 5-point scale was used to determine marital status: “with spouse”, “bereaved”,“divorced”, “never married”, and “others”. Respondents were divided into “spouse” and“others” groups.
2.11. Statistical Analysis Methods
The statistical software SAS 9.4 (SAS Institute Inc., Cary, NC, USA) was used to analyze
data and present results as mean ± standard deviation or number (%). Unpaired t-testand χ2 test were used to examine the association between hypertension and each item.
Logistic regression models were used to obtain age- and sex-adjusted ORs and 95% CIs to
identify factors associated with hypertension. Factors adjusted included age, sex, laughter,happiness, BMI, chewing ability, drinking habits, smoking habits, friend visits, hobbies, andmarital status. ORs were also obtained for men and women separately, and multivariate
logistic regression models were used for laughter and subjective happiness subanalyses.
All tests were two-tailed, and p < 0.05 was considered statistically significant.
3. Results
The study included 22,503 subjects with a prevalence of hypertension of 46.1% (10,364 subjects). The results showed that subjects with hypertension were older than those without
hypertension (Table 1). Hypertension was associated with factors such as laughter/subjective
happiness, BMI, assistance status, number of teeth, chewing ability, drinking habits, smoking
habits, number of friends met, marital status, employment status, and hobbies (Table 1).

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Table 1. Characteristics of the participants.
Hypertension
FactorsClass

Age (years)
Sex

Male
FemaleLaughter frequency/subjective
happiness

Infrequent laughter/low level ofsubjective happiness
Frequent laughter/low level ofsubjective happinessInfrequent laughter/high level ofsubjective happiness
Frequent laughter/high level ofsubjective happiness

Total

p-ValueYesNo

73.3 ± 6.1

74.4 ± 6.2

5771 (47.5)
6368 (52.5)4800 (46.3)
5564 (53.7)

10,571 (47.0)
11,932 (53.0)

0.0664044 (33.3)

3608 (34.8)

7652 (34.0)

0.043

1792 (14.8)

1570 (15.1)

3362 (14.9)

2941 (24.2)

2428 (23.4)

5369 (23.9)

3362 (27.7)2758 (26.6)

6120 (27.2)<0.001BMI

Underweight
NormalObesity1068 (9.2)
8612 (74.3)
1911 (16.5)

423 (4.3)
6526 (66.3)
2897 (29.4)

1491 (7.0)
15,138 (70.6)
4808 (22.4)<0.001

Caregiving/assistance status

Not needed
Needed but not received
Received

11,441 (96.9)
307 (2.6)
61 (0.5)9714 (96.4)
316 (3.1)
43 (0.4)

21,155 (96.7)
623 (2.8)
104 (0.5)

0.038Household income

JPY ≥2 million
JPY <2 million

7842 (73.5)
2827 (26.5)

6519 (72.6)
2455 (27.4)

14,361 (73.1)
5282 (26.9)

0.176

Number of teeth≥20 teeth<20 teeth

6228 (52.6)
5605 (47.4)

5077 (50.3)5011 (49.7)

11,305 (51.6)
10,616 (48.4)<0.001

Chewing ability

Anything
AlmostLimitedRarely chewing
Liquid diet4818 (39.8)
6522 (53.9)
728 (6.0)
28 (0.2)
10 (0.1)

3974 (38.5)
5717 (55.3)
595 (5.8)42 (0.4)
7 (0.1)8792 (39.2)
12,239 (54.5)
1323 (5.9)
70 (0.3)
17 (0.1)

0.027

Drinking habits

No drinker
Former drinker
Current drinker

7367 (61.4)
604 (5.0)4019 (33.5)5953 (58.1)
518 (5.1)
3771 (36.8)

13,320 (59.9)1122 (5.0)
7790 (35)<0.001

Smoking habits

No smoker
Former smoker
Current smoker

8722 (72.9)
1875 (15.7)
1366 (11.4)

7620 (74.6)
1700 (16.6)
896 (8.8)

16,342 (73.7)
3575 (16.1)
2262 (10.2)<0.001

TMIG-ICGood
Poor

9672 (79.7)
2467 (20.3)

8239 (79.5)
2125 (20.5)

17,911 (79.6)
4592 (20.4)

0.737

Frequency of seeing friends

4+ times/week
2–3 times/week
Once/week
1–3 times/month
A few times/year
Not seeing friends

2048 (17.6)
2282 (19.6)
1550 (13.3)
2640 (22.7)
2149 (18.5)
974 (8.4)

1710 (17.3)
2019 (20.4)
1317 (13.3)
2159 (21.9)
1821 (18.4)
854 (8.6)

3758 (17.5)4301 (20.0)2867 (13.3)
4799 (22.3)
3970 (18.4)
1828 (8.5)

0.518

Number of friends met

≥10
6–9
3–5
1 or 20 (none)4158 (35.7)
1633 (14.0)
2833 (24.3)
2067 (17.7)
967 (5.5)3362 (34.1)
1314 (13.3)
2534 (25.7)
1778 (18.0)
866 (5.8)7520 (35.0)2947 (13.7)
5367 (24.9)
3845 (17.9)
1833 (5.7)

0.021

Family living arrangement

OthersLiving alone

9974 (85.7)
1666 (14.3)

8475 (85.6)
1423 (14.4)

18,449 (85.7)
3089 (14.3)

0.894

Employment

Employed
Unemployed2846 (24.9)
8598 (75.1)

2213 (22.9)7455 (77.1)

5059 (24.0)
16,053 (76.0)<0.001

HobbiesYesNo

10,395 (87.8)
1444 (12.2)

8664 (86.1)
1401 (13.9)

19,059 (87.0)2845 (13.0)<0.0018791 (73.6)

7197 (70.7)

15,988 (72.3)<0.0013148 (26.4)

2981 (29.3)

6129 (27.7)

Marital status

With spouse (includingcommon-law marriage)
OthersData were expressed as means ± SDs or n (%). Differences between the two groups were analyzed using thechi-square test. BMI, body mass index; TMIG-IC, Tokyo Metropolitan Institute of Gerontology Index of Competence.

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Therefore, age- and sex-adjusted logistic regression analysis was conducted using
factors that showed significant differences in the unpaired t-test and χ2 test (Table 2). As per
the age- and sex-adjusted logistic regression analysis, age, female sex, obesity, infrequentchewing, former drinker, current drinker, no smoker, three to five friends met, and no
hobbies were positively associated with hypertension, whereas infrequent laughter/highlevel of subjective happiness, frequent laughter/high level of subjective happiness, being
underweight, and current smoker were negatively associated with hypertension.
Table 2. Results of the age- and sex-adjusted multivariate logistic regression analyses of the association between laughter frequency and subjective happiness and hypertension.
All

Men

Women

FactorsClass

Age- and SexAdjusted OR(95% CI)

MultipleAdjusted OR(95% CI) †(n = 22,503)

MultipleAdjusted OR(95% CI) ‡(n = 10,571)

MultipleAdjusted OR(95% CI) ‡(n = 11,932)

AgeContinuous

1.03 (1.03–1.03)

1.04 (1.03–1.04)

1.02 (1.01–1.03)

1.05 (1.04–1.06)

Sex

Female (ref. male)

1.04 (0.99–1.10)

1.23 (1.15–1.32)

1.00 (0.92–1.09)

0.99 (0.91–1.08)

0.96 (0.85–1.09)

1.03 (0.91–1.15)

0.90 (0.84–0.96)

0.91 (0.84–0.98)

0.85 (0.77–0.94)

0.97 (0.87–1.07)

0.92 (0.86–0.98)

0.91 (0.85–0.98)

0.90 (0.81–1.00)

0.93 (0.84–1.03)

0.49 (0.44–0.55)
2.06 (1.93–2.20)

0.49 (0.44–0.56)
2.06 (1.93–2.20)

0.44 (0.36–0.54)
1.93 (1.76–2.13)

0.54 (0.46–0.62)
2.19 (1.99–2.41)

Laughterfrequency/subjective
happiness

Frequent laughter/low level ofsubjective happiness (ref.
Infrequent laughter/low level ofsubjective happiness)
Infrequent laughter/high level ofsubjective happiness
Frequent laughter/high level ofsubjective happiness

BMI

Underweight (ref. normal)
Obesity

Caregiving/assistancestatusNeeded but not received (ref. notneeded)Received

1.05 (0.89–1.23)
0.69 (0.46–1.02)

Number of teeth<20 teeth (ref. ≥20 teeth)

1.00 (0.95–1.06)

Chewing ability

Almost (ref. anything)
LimitedRarely chewing
Liquid diet1.02 (0.96–1.08)
0.90 (0.80–1.01)
1.64 (1.01–2.65)
0.77 (0.29–2.02)

1.04 (0.98–1.10)
0.92 (0.82–1.04)
1.65 (1.00–2.72)
0.85 (0.31–2.29)

1.01 (0.93–1.10)
0.96 (0.81–1.14)
1.55 (0.80–3.00)
1.39 (0.39–5.04)

1.04 (0.96–1.13)
0.88 (0.73–1.05)
1.71 (0.79–3.69)
0.37 (0.07–1.97)

Drinking habits

Former drinker (ref. no drinker)
Current drinker

1.16 (1.02–1.32)
1.34 (1.25–1.42)

1.15 (1.00–1.31)
1.38 (1.29–1.47)

1.41 (1.21–1.65)
1.78 (1.63–1.94)

1.07 (0.81–1.41)
0.96 (0.87–1.07)

Smoking habits

Former smoker (ref. no smoker)
Current smoker

1.10 (1.01–1.19)
0.82 (0.75–0.91)

1.04 (0.95–1.13)
0.82 (0.75–0.91)

1.01 (0.92–1.11)
0.77 (0.69–0.86)

0.81 (0.62–1.05)
0.95 (0.76–1.17)

Number of friends met

6–9 (ref. ≥10)
3–5
1 or 20 (none)0.98 (0.90–1.07)
1.08 (1.01–1.16)
1.03 (0.95–1.12)
1.07 (0.96–1.18)

0.99 (0.91–1.08)
1.08 (1.01–1.17)
1.02 (0.94–1.11)
1.06 (0.95–1.18)

0.94 (0.82–1.08)
1.12 (1.00–1.24)
1.04 (0.92–1.17)
1.10 (0.95–1.26)

1.03 (0.92–1.15)
1.05 (0.95–1.16)
1.01 (0.90–1.14)
1.03 (0.86–1.23)

Employment

Unemployed (ref. employed)

1.00 (0.94–1.07)

Hobbies

No (ref. Yes)

1.11 (1.03–1.20)

1.09 (1.00–1.19)

1.07 (0.94–1.22)

1.10 (0.98–1.23)

Marital status

Others (ref. with spouse(including common-law
marriage))

1.04 (0.98–1.11)† Adjusted for age, sex, laughter frequency/subjective happiness, BMI, chewing ability, drinking habits, smoking
habits, number of friends met, hobbies, and marital status. Logistic regression model; a p value of <0.05 wasconsidered statistically significant. ‡ Adjusted for age, laughter frequency/subjective happiness, BMI, chewing
ability, drinking habits, smoking habits, number of friends met, hobbies, and marital status. Logistic regression
model; a p value of <0.05 was considered statistically significant. CI: confidence interval, OR: odds ratio,
Ref: reference, BMI: body mass index.

Next, multivariate logistic regression was conducted using factors that showed significant differences in the age- and sex-adjusted logistic regression model (Table 2). As per
the results, age, female sex, obesity, infrequent chewing, former drinker, current drinker,
three to five friends met, and no hobbies were positively associated with hypertension.

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7 of 12Meanwhile, infrequent laughter/high level of subjective happiness, frequent laughter/highlevel of subjective happiness, being underweight, and current smoker were negatively
associated with hypertension.
Multivariate logistic regression was conducted separately for men and women to
examine differences. In men, age (1.02, 95% CI: 1.01–1.03), obesity (1.93, 95% CI: 1.76–2.13),
former drinker (1.41, 95% CI: 1.21–1.65), and current drinker (1.78, 95% CI: 1.63–1.94)
had a positive association with hypertension. Infrequent laughter/high level of subjective
happiness (0.85, 95% CI: 0.77–0.94), being underweight (0.44, 95% CI: 0.36–0.54), and current
smoker (0.77, 95% CI: 0.69–0.86) had a negative association. Frequent laughter/high levelof subjective happiness had a negative trend toward hypertension (0.90, 95% CI: 0.81–1.00).
In women, age (1.05, 95% CI: 1.04–1.06) and obesity (2.19, 95% CI: 1.99–2.41) had a positive
association with hypertension, and being underweight (0.54, 95% CI: 0.46–0.62) had anegative association.
Finally, multivariate logistic regression analysis was performed separately for laughter
frequency and subjective happiness (Table 3). No significant association was found between frequent laughter and hypertension (OR: 0.98, 95% CI: 0.93–1.04). However, higher
subjective happiness was found to significantly lower the risk of hypertension comparedwith lower happiness (OR: 0.91, 95% CI: 0.86–0.97).
Table 3. Results of the multivariate logistic regression analysis of the association between the laughter
frequency or subjective happiness and hypertension.
Factors

Class

Multiple-Adjusted OR(95% CI) † (n = 22,503)

Multiple-Adjusted OR(95% CI) ‡ (n = 22,503)

AgeContinuous

1.04 (1.03–1.04)

1.04 (1.03–1.04)

Sex

Female (ref. male)

1.23 (1.15–1.31)

1.23 (1.15–1.32)

Laughter frequency

Frequent laughter (ref. infrequent laughter)

0.98 (0.93–1.04)

Subjective happinessHigh level of subjective happiness (ref. lowlevel of subjective happiness)

0.91 (0.86–0.97)

BMI

Underweight (ref. Normal)
Obesity

2.03 (1.80–2.29)
4.19 (3.68–4.76)

2.03 (1.80–2.29)
4.18 (3.67–4.75)

Chewing ability

Almost (ref. anything)
LimitedRarely chewing
Liquid diet1.04 (0.99–1.10)
0.94 (0.83–1.06)
1.69 (1.03–2.78)
0.85 (0.32–2.31)

1.04 (0.98–1.10)
0.92 (0.82–1.05)
1.65 (1.00–2.72)
0.85 (0.31–2.29)

Drinking habits

Former drinker (ref. no drinker)
Current drinker

1.15 (1.01–1.32)
1.38 (1.29–1.47)

1.15 (1.00–1.31)
1.38 (1.29–1.47)

Smoking habits

Former smoker (ref. no smoker)
Current smoker

1.04 (0.96–1.13)
0.83 (0.75–0.91)

1.04 (0.95–1.13)
0.82 (0.75–0.91)

Number of friends met

6–9 (ref. ≥10)
3–5
1 or 20 (none)1.00 (0.91–1.09)
1.09 (1.02–1.18)
1.04 (0.95–1.13)
1.07 (0.96–1.20)

0.99 (0.91–1.08)
1.08 (1.01–1.17)
1.02 (0.94–1.11)
1.06 (0.95–1.18)

Hobbies

No (ref. yes)

1.10 (1.01–1.20)

1.09 (1.00–1.19)† Adjusted for age, sex, laughter frequency, BMI, chewing ability, drinking habits, smoking habits, number ofpeople met, hobbies, and marital status. Logistic regression model; a p value of < 0.05 was considered statisticallysignificant. ‡ Adjusted for age, sex, subjective happiness, BMI, chewing ability, drinking habits, smoking habits,
number of people met, hobbies, and marital status. Logistic regression model; a value of p < 0.05 was considered
statistically significant. CI: confidence interval, OR: odds ratio, Ref: reference, BMI: body mass index.

4. Discussion
Several studies have shown a link between positive emotions and a reduced risk of hypertension [3,36,37]. This study also found that individuals with higher levels of subjective
happiness had a lower incidence of hypertension compared with those with lower levelsof happiness. One explanation for this relationship is that higher subjective happiness islinked to lower stress levels. Cortisol, a hormone associated with stress, increases withstress through the hypothalamic–pituitary–adrenal system. Men with higher subjective

Int. J. Environ. Res. Public Health 2023, 20, 5713

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happiness have lower cortisol levels in their saliva, regardless of their employment status [38]. Additionally, interventions aimed at inducing a positive mindset decrease cortisol
levels and reduce the cortisol response to stress [39]. These findings suggest that subjective
happiness may help prevent hypertension by reducing cortisol levels and the associatedstress response.
In the present study, regardless of laughter frequency, subjective happiness was negatively associated with hypertension in men. This finding could be explained by thedifference in the level of happiness between men and women. The percentage of women(54.6%) with a high level of subjective happiness was significantly higher than that of men(47.1%) (p < 0.001) (Data not shown). Using the Subjective Happiness Scale (SHS) [40] toassess subjective happiness among Japanese people in their 20s–70s, older age groups were
found to have a higher subjective happiness than younger ones. Furthermore, subjective
happiness was higher in people with a spouse than in those without. Finally, women
had a higher subjective happiness than men [41]. Moreover, happiness was inversely
related to cortisol levels and heart rate as assessed using the gait monitoring method [42].
Furthermore, a high heart rate can be a predictor of mortality and cardiovascular diseaserisk according to prospective epidemiologic studies. Moreover, a consistent association wasobserved between mortality and heart rate in men [43]. These findings suggest that men are
more susceptible to increased secretion of stress hormones and decreased cardiovascularfunction due to a lower subjective happiness than women. Promoting subjective happiness,at least for men, may be important to prevent cardiovascular disease.
In this study, infrequent social interaction and the absence of hobbies were positively
associated with hypertension. Ngamaba KH has reported a positive association between
subjective well-being and trust in other people, importance of friends and family, leisureactivities, and weekly attendance to religious services [44]. In adults and older adults livingin the rural areas of Japan, less television viewing and more mentally active sedentary
behaviors (e.g., talking to others, engaging in hobbies) were associated with greater happiness [45]. Ikigai may promote health and well-being among older Japanese adults [46].
These reports suggest that hobbies may improve subjective well-being. A cross-sectional
study using JAGES 2016 data showed that community-level civic engagement was negatively related to hypertension [47]. The current study showed that individuals with hobbies
were more likely to be socially active and have more opportunities to interact with others
compared with those without hobbies. Therefore, the number of social interactions andhobbies may be an indirect measure of social interaction. These results suggested that somehobbies might help prevent hypertension in older adults by promoting well-being andcommunicating with others.
Frequent laughter and high levels of subjective happiness were found to have anegative association with hypertension compared with infrequent laughter and lower
subjective happiness. However, the results showed that even with frequent laughter, if
subjective happiness was low, it was not related to hypertension. A separate analysis oflaughter frequency alone also showed no significant link to hypertension. Despite this,previous studies have reported a higher risk of cardiovascular disease among individuals
with infrequent laughter [10] and increased blood pressure in men who laughed lessthan once a week [48]. Additionally, Low et al. conducted a study among nursing homeresidents and found that those who received weekly humor therapy for 9–12 weeks had
fewer symptoms of agitation and increased happiness compared to the control group [49].
Another study by Ghodsbin et al. reported that 90 min of laughter therapy twice a week
for 6 weeks improved anxiety, insomnia, and physical symptoms in community residents
aged 60 and older [50]. Based on these reports and the results of this study, further research
may be needed to clarify the relationship between laughter frequency and hypertension.
Further studies, including interventions to increase laughter frequency and assess theimpact on subjective happiness and blood pressure, seem necessary.
This study found that individuals with poor chewing ability had a higher likelihoodof having hypertension. This suggests that the oral environment may play a role inInt. J. Environ. Res. Public Health 2023, 20, 5713

9 of 12hypertension. A study of older adults aged 70 or older showed that severe gum disease may
be positively associated with hypertension in this age group [51]. Additionally, longitudinalstudies have linked periodontal disease to the development of metabolic syndrome [52].
These findings suggest that oral health in older adults may be a contributing factor to
uncontrolled blood pressure. The results of this study suggest that promoting good oral
hygiene could be important in preventing hypertension in older adults.
This study had several limitations. First, being a cross-sectional study, we wereunable to establish a causal relationship between hypertension, laughter frequency, andsubjective happiness. Second, the study was based on self-administered questionnaires,
which could lead to recall bias and difficulty in determining the required frequency oflaughter and the level of subjective happiness to prevent hypertension. Third, in thisstudy, hypertension was solely defined by self-reported data. Meanwhile, details on
physician’s diagnosis, management, and disease duration remain unclear. According to theliterature, self-reported information about hypertension has shown a substantial agreementwith medical records [53]. However, other studies have revealed that self-reports may
significantly underestimate the prevalence of hypertension [54]. Therefore, it is imperative
to acknowledge that hypertension may have been underestimated in this study as well.
Finally, the study was conducted on a population of individuals aged ≥65 years; thus, it isuncertain whether the results apply to other age groups.
5. Conclusions
This study suggests that having more opportunities to feel happiness may be importantin preventing hypertension. However, it is important to exercise caution in overly pursuing
an increase in subjective happiness, as focusing too much on subjective happiness can leadto disappointment and negatively impact one’s overall well-being.
Author Contributions: Conceptualization, F.H., Y.S. and T.O.; methodology and formal analysis, F.H.
and Y.S.; validation, T.O., K.S., N.K. and K.K.; investigation and data curation, T.O., K.S., N.K. andK.K.; resources, T.O., K.S., N.K., and K.K.; writing and visualization, F.H. and Y.S.; supervision, T.O.;
project administration and funding acquisition, T.O., K.S., N.K. and K.K. All authors have read andagreed to the published version of the manuscript.
Funding: This work was supported by JSPS (Japan Society for the Promotion of Science) KAKENHI(19H03901 and 23H03167), and Japan Agency for Medical Research and Development (AMED)(22rea522104h0001 and 23rea522104h0002).
Institutional Review Board Statement: The protocol and informed consent procedures for this study
were approved by the Ethics Committee on Research of Human Subjects of Nihon Fukushi University(13–14). This study was conducted in accordance with the principles of the Declaration of Helsinki.
Informed Consent Statement: JAGES participants were informed that participation in the study was
voluntary and that completing and returning the questionnaire indicated their consent to participate
in the study.
Data Availability Statement: Additional detailed data for this study are available upon reasonable
written request to the corresponding author.
Acknowledgments: This study used the data from the JAGES (the Japan Gerontological Evaluation
Study). This study was supported by Grant-in-Aid for Scientific Research (15H01972, 15H04781,
15H05059, 15K03417, 15K03982, 15K16181, 15K17232, 15K18174, 15K19241, 15K21266, 15KT0007,
15KT0097, 16H05556, 16K09122, 16K00913, 16K02025, 16K12964, 16K13443, 16K16295, 16K16595,
16K16633, 16K17256, 16K17281, 16K19247, 16K19267, 16K21461, 16K21465, 16KT0014, 17K04305,
17K04306, 25253052, 25713027, 26285138, 26460828, 26780328, 18H03018, 18H04071, 18H03047,
18H00953, 18H00955, 18KK0057, 19H03901, 19H03915, 19H03860, 19K04785, 19K10641, 19K11657,
19K19818, 19K19455, 19K24060, 19K20909, 20H00557) from JSPS (Japan Society for the Promotion of
Science); Health Labour Sciences Research Grants (H26-Choju-Ippan-006, H27-Ninchisyou-Ippan-001
H28- Choju-Ippan-002, H28- Ninchisyou-Ippan-002, H30-Kenki-Ippan-006,H29-Chikyukibo-Ippan001, H30-Jyunkankinado-Ippan-004, 19FA1012, 19FA2001, 21FA1012, 21K19635); Research project
on health and welfare promotion for the elderly from the Ministry of Health, Labour and Welfare,Int. J. Environ. Res. Public Health 2023, 20, 5713

10 of 12

Japan; the Research and Development Grants for Longevity Science from Japan Agency for Medical
Research and development (AMED) (JP18dk0110027, JP18ls0110002, JP18le0110009, JP20dk0110034,
JP21lk0310073, JP21dk0110037); the Research Funding for Longevity Sciences from National Center
for Geriatrics and Gerontology (24-17, 24-23, 29-42, 30-30, 30-22, 20-19, 21-20); Open Innovation
Platform with Enterprises, Research Institute and Academia (OPERA, JPMJOP1831) from the Japan
Science and Technology (JST); a grant from the Japan Foundation For Aging And Health (J09KF00804);
a grant from Innovative Research Program on Suicide Countermeasures (1-4); a grant from Sasakawa
Sports Foundation; a grant from Japan Health Promotion & Fitness Foundation; a grant from Chiba
Foundation for Health Promotion & Disease Prevention; the 8020 Research Grant for fiscal 2019from the 8020 Promotion Foundation (adopted number: 19-2-06); and grants from Meiji Yasuda LifeFoundation of Health and Welfare. The views and opinions expressed in this article are those of
the authors and do not necessarily reflect the official policy or position of the respective fundingorganizations.
Conflicts of Interest: The authors declare no conflict of interest.

References
1.
2.
3.
4.
5.
6.
7.
8.

9.
10.
11.
12.
13.
14.

15.

16.
17.
18.

19.

Boehm, J.K.; Peterson, C.; Kivimaki, M.; Kubzansky, L. A prospective study of positive psychological well-being and coronary
heart disease. Health Psychol. 2011, 30, 259–267. [CrossRef]
Boehm, J.K.; Chen, Y.; Williams, D.R.; Ryff, C.D.; Kubzansky, L.D. Subjective well-being and cardiometabolic health: An 8-11 year
study of midlife adults. J. Psychosom. Res. 2016, 85, 1–8. [CrossRef]
Trudel-Fitzgerald, C.; Boehm, J.K.; Kivimaki, M.; Kubzansky, L.D. Taking the tension out of hypertension: A prospective study ofpsychological well-being and hypertension. J. Hypertens. 2014, 32, 1222–1228. [CrossRef]
Kim, E.S.; Sun, J.K.; Park Nansook Peterson, C. Purpose in life and reduced incidence of stroke in older adults: “The Health andRetirement Study”. J. Psychosom. Res. 2013, 74, 427–432. [CrossRef] [PubMed]
Lambiase, M.J.; Kubzansky, L.D.; Thurston, R.C. Positive psychological health and stroke risk: The benefits of emotional vitality.
Health Psychol. 2015, 34, 1043–1046. [CrossRef] [PubMed]
Ostir, G.V.; Markides, K.S.; Peek, M.K.; Goodwin, J.S. The association between emotional well-being and the incidence of stroke inolder adults. Psychosom. Med. 2001, 63, 210–215. [CrossRef] [PubMed]
Okely, J.A.; Gale, C.R. Well-being and chronic disease incidence: The English longitudinal study of ageing. Psychosom. Med. 2016,
78, 335–344. [CrossRef] [PubMed]
Sakurada, K.; Konta, T.; Watanabe, M.; Ishizawa, K.; Ueno, Y.; Yamashita, H.; Kayama, T. Associations of frequency of laughterwith risk of all-cause mortality and cardio-vascular disease incidence in a general population: Findings from the Yamagata study.
J. Epidemiol. 2020, 30, 188–193. [CrossRef]
Miller, M.; Fry, W.F. The effect of mirthful laughter on the human cardiovascular system. Med. Hypotheses 2009, 73, 636–639.
[CrossRef] [PubMed]
Hayashi, K.; Kawachi, I.; Ohira, T.; Kondo, K.; Shirai, K.; Kondo, N. Laughter is the Best Medicine? A Cross-Sectional Study ofCardiovascular Disease Among Older Japanese Adults. J. Epidemiol. 2016, 26, 546–552. [CrossRef]
Dolgoff-Kaspar, R.; Baldwin, A.; Johnson, M.S.; Edling, N.; Sethi, G.K. Effect of laughter yoga on mood and heart rate variability
in patients awaiting organ transplantation: A pilot study. Altern. Ther. Health Med. 2012, 18, 61–66. [PubMed]
Sakai, Y.; Takayanagi, K.; Ohno, M.; Inose, R.; Fujiwara, H. A trial of improvement of immunity in cancer patients by laughter
therapy. Jpn. Hosp. 2013, 32, 53–59.
Hayashi, T.; Tsujii, S.; Iburi, T.; Tamanaha, T.; Yamagami, K.; Ishibashi, R.; Hori, M.; Sakamoto, S.; Ishii, H.; Murakami, K. Laughter
up-regulates the genes related to NK cell activity in diabetes. Biomed. Res. 2007, 28, 281–285. [CrossRef]
Hirosaki, M.; Ohira, T.; Kajiura, M.; Kiyama, M.; Kitamura, A.; Sato, S.; Iso, H. Effects of a laughter and exercise program on
physiological and psychological health among community-dwelling elderly in Japan: Randomized controlled trial. Geriatr.
Gerontol. Int. 2013, 13, 152–160. [CrossRef] [PubMed]
Vlachopoulos, C.; Xaplanteris, P.; Alexopoulos, N.; Aznaouridis, K.; Vasiliadou, C.; Baou, K.; Stefanadi, E.; Stefanadis, C.
Divergent effects of laughter and mental stress on arterial stiffness and central hemodynamics. Psychosom. Med. 2009, 71, 446–453.
[CrossRef] [PubMed]
Miller, M.; Mangano, C.; Park, Y.; Goel, R.; Plotnick, G.D.; Vogel, R.A. Impact of cinematic viewing on endothelial function. Heart
2006, 92, 261–262. [CrossRef]
Argyle, M. Is happiness a cause of health? Psychol. Health 1997, 12, 769–781. [CrossRef]
Shahidi, M.; Mojtahed, A.; Modabbernia, A.; Mojtahed, M.; Shafiabady, A.; Delavar, A.; Honari, H. Laughter yoga versus groupexercise program in elderly depressed women: A randomized controlled trial. Int. J. Geriatr. Psychiatry 2011, 26, 322–327.
[CrossRef]
Funakubo, N.; Eguchi, E.; Hayashi, R.; Hirosaki, M.; Shirai, K.; Okazaki, K.; Nakano, H.; Hayashi, F.; Omata, J.; Imano, H.; et al.
Effects of a laughter program on body weight and mental health among Japanese people with metabolic syndrome risk factors:
A randomized controlled trial. BMC Geriatr. 2022, 22, 361. [CrossRef]

Int. J. Environ. Res. Public Health 2023, 20, 5713

20.
21.
22.
23.

24.
25.

26.

27.
28.

29.
30.
31.
32.

33.
34.

35.

36.
37.
38.
39.
40.
41.
42.
43.
44.
45.

11 of 12

Yim, J. Therapeutic Benefits of Laughter in Mental Health: A Theoretical Review. Tohoku J. Exp. Med. 2016, 239, 243–249.
[CrossRef]
Kotsis, V.; Stabouli, S.; Bouldin, M.; Low, A.; Toumanidis, S.; Zakopoulos, N. Impact of obesity on 24-hour ambulatory bloodpressure and hypertension. Hypertension 2005, 45, 602–607. [CrossRef] [PubMed]
Obesity. Preventing and Managing the Global Epidemic: Report of a WHO Consultation on Obesity, Geneva. 3. Global Prevalenceand Secular Trends in Obesity. Available online: https://apps.who.int/iris/handle/10665/42330 (accessed on 3 May 2022).
Yoshiike, N.; Matsumura, Y.; Zaman, M.M.; Yamaguchi, M. Descriptive epidemiology of body mass index in Japanese adults
in a representative sample from the National Nutrition survey 1990–1994. Int. J. Obes. Relat. Metab. Disord. 1998, 22, 684–687.
[CrossRef] [PubMed]
Examination Committee of Criteria for ‘Obesity Disease’ in Japan; Japan Society for the Study of Obesity. New criteria for ‘obesity
disease’ in Japan. Circ. J. 2002, 66, 987–992. [CrossRef]
Tamada, Y.; Takeuchi, K.; Yamaguchi, C.; Saito, M.; Ohira, T.; Shirai, K.; Kondo, K. Does laughter predict onset of functional
disability and mortality among older Japanese adults? The JAGES prospective cohort study. J. Epidemiol. 2021, 31, 301–307.
[CrossRef]
Niklas, A.; Flotyńska, A.; Puch-Walczak, A.; Polakowska, M.; Topór-Madry,˛
R.; Polak, M. WOBASZ II investigators. Prevalence,awareness, treatment and control of hypertension in the adult Polish population—Multi-center National Population Health
Examination Surveys—WOBASZ studies. Arch. Med. Sci. 2018, 14, 951–961. [CrossRef] [PubMed]
Ministry of Health, Labour and Welfare. National Health and Nutrition Survey. 2014. Available online: https://www.mhlw.go.
jp/stf/houdou/0000106405.html (accessed on 3 May 2022).
Martin-Cabezas, R.; Seelam, N.; Petit, C.; Agossa, K.; Gaertner, S.; Tenenbaum, H.; Davideau, J.L.; Huck, O. Association between
periodontitis and arterial hypertension: A systematic re-view and meta-analysis. Am. Heart J. 2016, 180, 98–112. [CrossRef][PubMed]
Ministry of Health, Labour and Welfare. National Health and Nutrition Survey. 2013. Available online: https://www.mhlw.go.
jp/stf/houdou/0000067890.html (accessed on 3 May 2022).
Marmot, M.G.; Elliott, P.; Shipley, M.J.; Dyer, A.R.; Ueshima, H.U.; Beevers, D.G.; Stamler, R.; Kesteloot, H.; Rose, G.; Stamler, J.
Alcohol and blood pressure: The INTERSALT study. BMJ 1994, 308, 1263–1267. [CrossRef]
Virdis, A.; Giannarelli, C.; Neves, M.F.; Taddei, S.; Ghiadoni, L. Cigarette smoking and hypertension. Curr. Pharm. Des. 2010, 16,
2518–2525. [CrossRef]
Hozawa, A.; Okamura, T.; Murakami, Y.; Kadowaki, T.; Okuda, N.; Takashima, N.; Hayakawa, T.; Kita, Y.; Miura, K.; Nakamura,Y.; et al. High blood pressure in middle age is associated with a future decline in activities of daily living. NIPPON DATA80.
J. Hum. Hypertens. 2009, 23, 546–552. [CrossRef]
Koyano, W.; Shibata, H.; Nakazato, K.; Haga, H.; Suyama, Y. Measurement of competence: Reliability and validity of the TMIG
Index of Competence. Arch. Gerontol. Geriatr. 1991, 13, 103–116. [CrossRef]
Kim, K.; Jung, S.J.; Baek, J.M.; Yim, H.W.; Jeong, H.; Kim, D.J.; Park, S.; Youm, Y.; Kim, H.C. Associations between social network
properties and metabolic syndrome and the mediating effect of physical activity: Findings from the Cardiovascular and Metabolic
Diseases Etiology Research Center (CMERC) Cohort. BMJ Open Diabetes Res. Care 2020, 8, e001272. [CrossRef] [PubMed]
Fu, R.; Noguchi, H.; Tachikawa, H.; Aiba, M.; Nakamine, S.; Kawamura, A.; Takahashi, H.; Tamiya, N. Relation between social
network and psychological distress among middle-aged adults in Japan: Evidence from a national longitudinal survey. Soc. Sci.
Med. 2017, 175, 58–65. [CrossRef]
Ostir, G.V.; Berges, I.M.; Markides, K.S.; Ottenbacher, K.J. Hypertension in older adults and the role of positive emotions.
Psychosom. Med. 2006, 68, 727–733. [CrossRef]
Richman, L.S.; Kubzansky, L.; Maselko, J.; Kawachi, I.; Choo, P.; Bauer, M. Positive emotion and health: Going beyond thenega-tive. Health Psychol. 2005, 24, 422–429. [CrossRef]
Steptoe, A.; Wardle, J. Positive affect and biological function in everyday life. Neurobiol. Aging 2005, 26, 108–112. [CrossRef][PubMed]Nicolson, N.A.; Peters, M.L.; In den Bosch-Meevissen, Y.M.C. Imagining a positive future reduces cortisol response to awaken-ing
and reactivity to acute stress. Psychoneuroendocrinology 2020, 116, 104677. [CrossRef] [PubMed]
Lyubomirsky, S.; Lepper, H.S. A measure of subjective happiness: Preliminary reliability and construct validation. Soc. Indic. Res.
1999, 46, 137–155. [CrossRef]
Shimai, S.; Yamamiya, Y.; Fukuda, S. Subjective happiness among Japanese adults: An upward tendency associated with age.
Nihon Koshu Eisei Zasshi 2018, 65, 553–562. (In Japanese)
Steptoe, A.; Wardle, J.; Marmot, M. Positive affect and health-related neuroendocrine, cardiovascular, and inflammatory pro-cesses.
Proc. Natl. Acad. Sci. USA 2005, 102, 6508–6512. [CrossRef]
Kannel, W.B.; Kannel, C.; Paffenbarger, R.S., Jr.; Cupples, L.A. Heart rate and cardiovascular mortality: The Framingham Study.
Am. Heart J. 1987, 113, 1489–1494. [CrossRef]
Ngamaba, K.H. Determinants of subjective well-being in representative samples of nations. Eur. J. Public Health 2017, 27, 377–382.
[CrossRef] [PubMed]
Yasunaga, A.; Koohsari, M.J.; Shibata, A.; Ishii, K.; Miyawaki, R.; Araki, K.; Oka, K. Sedentary Behavior and Happiness:
The Mediation Effects of Social Capital. Innov. Aging 2021, 5, igab044. [CrossRef] [PubMed]

Int. J. Environ. Res. Public Health 2023, 20, 5713

46.

47.

48.

49.

50.

51.
52.
53.

54.

12 of 12

Okuzono, S.S.; Shiba, K.; Kim, E.S.; Shirai, K.; Kondo, N.; Fujiwara, T.; Kondo, K.; Lomas, T.; Trudel-Fitzgerald, C.; Kawachi, I.;et al. Ikigai and subsequent health and wellbeing among Japanese older adults: Longitudi-nal outcome-wide analysis. Lancet Reg.
Health West. Pac. 2022, 21, 100391. [CrossRef]
Nakagomi, A.; Tsuji, T.; Hanazato, M.; Kobayashi, Y.; Kondo, K. Association between community-level social participation andself-reported hypertension in older Japanese: A JAGES multilevel cross-sectional study. Am. J. Hypertens. 2019, 32, 503–514.
[CrossRef]
Ikeda, S.; Ikeda, A.; Yamagishi, K.; Hori, M.; Kubo, S.; Sata, M.; Okada, C.; Umesawa, M.; Sankai, T.; Kitamura, A.; et al.
Longitudinal trends in blood pressure associated with the frequency of laughter: The circulatory risk in communities study(CIRCS), a longitudinal study of the Japanese general population. J. Epidemiol. 2021, 31, 125–131. [CrossRef] [PubMed]
Low, L.F.; Goodenough, B.; Fletcher, J.; Xu, K.; Casey, A.N.; Chenoweth, L.; Fleming, R.; Spitzer, P.; Bell, J.P.; Brodaty, H. The effectsof humor therapy on nursing home residents measured using obser-vational methods: The SMILE cluster randomized trial. J. Am.
Med. Dir. Assoc. 2014, 15, 564–569. [CrossRef]
Ghodsbin, F.; Ahmadi, Z.S.; Iran Jahanbin, I.; Farkhondeh Sharif, F. The effects of laughter therapy on general health of elderly
people referring to jahandidegan community center in shiraz, iran: A randomized controlled trial. Int. J. Community Based Nurs.
Midwif. 2015, 3, 31–38.
Rivas-Tumanyan, S.; Campos, M.; Zevallos, J.C.; Joshipura, K.J. Periodontal disease, hypertension, and blood pressure amongolder adults in Puerto Rico. J. Periodontol. 2013, 84, 203–211. [CrossRef]
Morita, T.; Yamazaki, Y.; Mita, A.; Takada, K.; Seto, M.; Nishinoue, N.; Sasaki, Y.; Motohashi, M.; Maeno, M. A cohort study on theassociation between periodontal disease and the development of metabolic syndrome. J. Periodontol. 2010, 81, 512–519. [CrossRef]
Okura, Y.; Urban, L.H.; Mahoney, D.W.; Jacobsen, S.J.; Rodeheffer, R.J. Agreement between self-report questionnaires and medical
record data was substantial for diabetes, hypertension, myocardial infarction and stroke but not for heart failure. J. Clin. Epidemiol.
2004, 57, 1096–1103. [CrossRef]
Goldman, N.; Lin, I.F.; Weinstein, M.; Lin, Y.H. Evaluating the quality of self-reports of hypertension and diabetes. J. Clin.
Epidemiol. 2003, 56, 148–154. [CrossRef] [PubMed]

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