Blood pressure (BP) varies according to many internal and external factors. There are several distinctive rhythmic variations in BP including diurnal (or circadian) variation, and behavioral factors have an important role in diurnal BP variation. BP rises sharply on waking in the morning and falls during sleep at night, although it varies with changes in mental and physical activities during daytime and nighttime.1, 2, 3, 4 In addition to the awake and sleep cycle, many behavioral factors, such as mental stress, exercise, food consumption, changes in body weight, dietary intake of sodium and other electrolytes, drinking and smoking habits, consumption of coffee and tea, and bathing, influence both the level and variation in BP.5, 6, 7, 8

Understanding the influences of those behavioral factors on diurnal BP variation is important for the management of hypertension because alterations in diurnal BP variation due to behavioral factors are observed in many hypertensive subjects.9, 10 It has been shown that ambulatory BP monitoring is useful for assessing the influence of behavioral factors as well as the effects of lifestyle modifications on the level and pattern of BP throughout the day.11, 12 In this review article, I would like to summarize the effects of behavioral factors on diurnal BP variation with respect to the pathophysiology of hypertension and the effects of lifestyle modifications on 24-h BP.

Diurnal BP variation in relation to mental and physical activity

Awake and sleep cycle

Diurnal variation in BP is well recognized. Usually, BP rapidly rises on wakening in the early morning, reaches a plateau during the morning, falls slightly in the early afternoon and rises again in the early evening.1, 2 BP decreases gradually in the late evening, drops sharply after falling asleep and is lowest during sleep. These changes in BP are largely attributed to mental and physical activities, and the sympathetic nervous system has a crucial role in the generation of diurnal BP variation.9, 13, 14, 15 It has been shown that diurnal changes in BP coincide with changes in heart rate and the levels of plasma and urinary catecholamines.13, 14, 15, 16 It also has been shown that BP is high during nighttime working hours and low during daytime sleeping hours in shift workers, although the dip in BP during sleeping hours may be attenuated at the beginning of the night shift.17, 18 These results indicate that the endogenous clock has a minor role in the generation of BP variation associated with the awake and sleep cycle.

The morning rise in BP mainly depends on physical activity after waking. It has been shown that BP changes little after waking when the subjects remain supine, but rises rapidly when they get out of bed.19 It is also reported that the magnitude of the morning rise in BP is correlated with changes in physical activity.20 Although the morning rise in BP is a physiological phenomenon, some hypertensive patients show an exaggerated rise in BP that is called the morning surge. Cardiovascular events such as myocardial infarction and stroke occur most frequently in the early morning, and the morning surge in BP appears to have an important role in the onset of these cardiovascular events.3, 21, 22 On the other hand, the nighttime dip in BP is also altered in many hypertensive patients. A number of studies have shown that nondipping of the nighttime BP is associated with target organ damage and cardiovascular disease in hypertensive patients.23, 24

Mental and physical stress

As the variation in BP is closely associated with mental and physical activities, mental and physical stress causes not only acute changes in BP but also modifies diurnal BP variation. The morning rise in BP mainly depends on physical activity; however, mental and physical stress associated with housework and going to work in the early morning may cause an exaggerated BP surge and morning hypertension (Table 1).25 Many hypertensive patients experience a higher morning BP at home on weekdays compared with the weekend. In a study using repeated ambulatory BP monitoring, the morning surge in BP was largest on Monday among a community dwelling population.26

Table 1 Subtypes of hypertension according to diurnal BP variation and related behavioral factors (from ref. 25 with modifications)

Mental and physical stress elevates BP during the daytime and may cause daytime hypertension (Table 1).25 It has been shown that job stress is related to higher BP at work in normotensive subjects.5, 27 Another study showed that the BP response to daily stress was enhanced in hypertensive subjects compared with normotensive subjects.28 Ambulatory BP during work was 10% higher than home BP in hypertensives, but the difference was only 3% in normotensives in this study. It was also reported that more than 20% of civil servants showed worksite hypertension, although they were found to be normotensive during a health examination.29

Stress in daily life may be relieved by hospitalization. In our study, hospitalization tended to lower daytime BP and diminished the day–night BP difference in hypertensive patients (Table 2).30 It should be mentioned that many patients were dippers during the outpatient period but became nondippers after admission. Regarding the effect of stress management, it has been shown that transcendental and contemplative meditation effectively lowered ambulatory BP in clinical trials.31, 32

Table 2 Mean 24-h, daytime and nighttime blood pressures during outpatient and inpatient periods in hypertensive patients (from ref. 30 with modifications)

Mental and physical activities also affect nighttime BP. A study using beat-to-beat BP and electroencephalographic measurements revealed that frequent cuff inflation during ambulatory BP monitoring caused arousal from sleep and elevated BP.33 In another study using sleep actigraphy, nondippers showed higher activity levels and spent less time asleep when in bed compared with dippers.34 Therefore, sleep disturbance elevates BP and may contribute to the nondipping of BP at night.


BP rises during exercise but falls after exercise. This exercise-induced BP elevation is due to an increase in cardiac output, and its magnitude depends on the intensity of exercise. Postexercise hypotension is associated with a decrease in total peripheral resistance and persists for several hours.35 These exercise related changes in BP affect diurnal BP variation.

A sedentary lifestyle is a risk factor for hypertension, and guidelines recommend regular exercise for the management of hypertension. A number of intervention studies have demonstrated the BP-lowering effect of exercise.36 Several studies have also shown that regular exercise lowers ambulatory BP in normotensive and hypertensive subjects. Miyai et al.37 reported that bicycle exercise reduced daytime BP and attenuated BP elevation during exercise without changing nighttime BP in normotensive subjects. Park et al.38 studied the effect of time of day on the influence of exercise in hypertensive patients. In their study, morning exercise decreased daytime BP in both dippers and nondippers, whereas evening exercise lowered nighttime BP in nondippers but not dippers. These findings suggest that the effect of exercise on 24-h BP varies according to the time of exercise and the type of nocturnal BP dipping.

Influence of eating behavior and obesity on diurnal BP variation

Food intake and postprandial hypotension

BP slightly rises during food intake but falls after eating. This BP elevation is due to increased physical activity during eating. The reduction in BP observed after eating is caused by a decrease in total peripheral resistance because of visceral vasodilation.39, 40 This BP reduction is small in healthy young subjects, but may be large in elderly subjects and hypertensive subjects and profound in patients with autonomic failure.40, 41, 42, 43 It is also greater after high-carbohydrate meals compared with high-fat meals.39 Although the mechanisms of postprandial hypotension have not been fully clarified, inadequate sympathetic nervous system compensation due to an impaired baroreceptor reflex, insulin-induced vasodilation and the release of vasodilatory gastrointestinal polypeptides may be involved. The postprandial BP reduction peaks at about 1 h after eating and persists for more than 2 h. Thus, it influences diurnal BP variation, particularly in elderly subjects with hypertension.

Obesity and sleep apnea

The relationship between obesity and hypertension is well known, and guidelines recommend weight reduction for overweight/obese subjects in order to manage hypertension. Obese subjects have higher daytime and nighttime BP compared with lean subjects; however, these subjects may also show altered diurnal BP variations and an increased prevalence of the nondipping status.44 Obstructive sleep apnea is prevalent among obese subjects and may contribute to hypertension in these individuals.45 It has been shown that obstructive sleep apnea predominantly increases nighttime BP and its variability because of BP surges due to hypoxia/hypercapnea during episodes of apnea.45, 46 Therefore, obesity and sleep apnea may cause nighttime hypertension (Table 1).

A number of studies have demonstrated that weight reduction is effective for lowering BP in hypertensive patients. In our studies, weight reduction with a hypocaloric diet was associated with significant decreases in 24-h BP in overweight/obese patients with hypertension, and the reductions in daytime and nighttime BP were comparable.47, 48 However, it has also been shown that weight reduction by gastric bypass surgery normalizes the blunted nocturnal fall observed in the BP of morbidly obese patients with impaired circadian BP.49

Dietary sodium and other electrolytes

Dietary sodium intake is closely related to BP and hypertension. The hypertensive effect of a high sodium diet is observed throughout the day, and sodium restriction decreases daytime and nighttime BP similarly in hypertensive patients.7 However, the degree of BP elevation induced by a high-sodium diet might be greater during night than day in salt-sensitive patients. It has been shown that these patients are likely to be nondippers when they consume much salt, but become dippers during sodium restriction.50

Sodium metabolism also shows diurnal variation, which is related to BP. Urinary sodium excretion is relatively high during the daytime and low during nighttime in normotensive and hypertensive subjects.16 This diurnal variation in sodium excretion is diminished or reversed in hypertensive nondippers.51 Impaired sodium excretion capacity in salt-sensitive patients may result in the elevation of nocturnal BP to stimulate natriuresis in order to restore sodium balance (Table 1).

The dietary intake of potassium, calcium and magnesium is inversely related to the BP, and clinical studies have shown significant reductions in BP after supplementation of these minerals.36 Current guidelines encourage the consumption of fruits and vegetables that are rich in potassium and magnesium and dairy products that are rich in calcium for the management of hypertension. In our studies, potassium, calcium and magnesium supplementation decreased ambulatory BP in hypertensive patients although the effect of calcium was not significant.52, 53, 54 We also observed that the hypotensive effects of potassium and calcium tended to be greater during nighttime than daytime, but the effect of magnesium was the same throughout the day. It has been shown that potassium and calcium mainly lower BP by natriuresis. Therefore, dietary intake of potassium and calcium may affect diurnal BP variation although their influence is small.

Diurnal BP variation in relation to drinking and smoking

Alcohol intake

The hypertensive effect of alcohol has been demonstrated in a number of observational and clinical studies.36, 55 However, alcohol has both pressor and depressor actions, and the latter is obvious in Asian subjects, especially in those who show alcohol flush. In our study, BP decreased and heart rate increased for several hours after alcohol ingestion in hypertensive patients.56 We also examined the effects of repeated alcohol intake in the evening under standardized conditions.7, 57 After 1 week, the BP of hypertensive patients decreased in the evening but increased in the early morning (Figure 1). We further investigated the effects of alcohol restriction for 4 weeks in habitual drinkers with hypertension.58, 59 In these studies, morning and daytime BP fell but evening and nighttime BP rose with alcohol restriction while mean BP did not change. Many dippers became nondippers and many extreme-dippers became dippers with alcohol restriction. Thus, drinking habit seems to be a risk factor for morning hypertension (Table 1). An elevation in morning BP without changes in mean 24-h BP in habitual drinkers was also observed in population-based epidemiological studies in Japan.60, 61

Figure 1
figure 1

Blood pressure and heart rate at the end of the control period (open circles) and alcohol period (7 days, solid circle) in hypertensive patients. *P<0.05 between the two periods. Adopted from ref. 7.

However, the effect of alcohol on 24-h BP may differ between Orientals and Caucasians. Rakic et al.62 observed elevations in daytime and mean 24-h BP without a change in nighttime BP after repeated alcohol consumption in Australian men. This racial difference is likely to be due to genetic variation in aldehyde dehydrogenase 2 (ALDH2) activity.55 Subjects with the ALDH2*2 genotype, which is common in Mongoloids but rare in Caucasians and Africans, show facial flush, tachycardia and hypotension after drinking alcohol because of the accumulation of acetaldehyde, but these changes are very small in subjects with the ALDH2*1 genotype.

Cigarette smoking

In epidemiological studies, smokers usually do not show higher levels of BP than nonsmokers. However, smoking acutely increases BP and heart rate by activating the sympathetic nervous system. Studies using ambulatory BP monitoring have revealed that daytime BP, but not nighttime BP, is higher in smokers than in nonsmokers and is higher on smoking than on nonsmoking days.8, 63 Therefore, smoking habit is associated with an increase in the day–night BP difference and is a cause of daytime hypertension (Table 1).

As smokers usually do not smoke in the medical environment, their BP may be normal when they visit a clinic but high during their daily life. It has been shown that the prevalence of current smokers was highest in the masked hypertension group among normotensive and hypertensive subjects.64

Effects of coffee and tea consumption

Coffee and tea contain a number of chemicals including caffeine and flavonoids. These beverages as well as cocoa and chocolate have certain effects on BP and cardiovascular disease although guidelines for the management of hypertension do not mention their consumption.

It has been shown that the consumption of coffee and tea acutely elevates BP.65, 66 This pressor response is usually moderate (about 10 mm Hg) and short in duration (about 1 h). The acute rise in BP is largely attributed to activation of the sympathetic nervous system by caffeine although other mechanism(s) may be involved. This effect can counteract the postprandial hypotension after a meal. However, flavonoids act to improve vascular function and antihypertensive effects of tea and cocoa have also been suggested.67, 68, 69 Meta-analyses of controlled clinical trials showed a small increase in BP associated with coffee consumption, no change due to tea consumption, and a significant reduction in BP after cocoa consumption.69, 70

Several studies have assessed the effect of caffeinated and flavonoid-rich drinks or food on 24-h BP. Small but significant reductions in morning, afternoon and evening BP were observed after the cessation of caffeinated coffee consumption in normotensive subjects.71 In another study, 24-h BP increased in hypertensive patients but not in normotensive subjects after coffee consumption.72 On the other hand, a significant reduction in 24-h BP and an improvement of endothelial function were shown in hypertensive patients after the consumption of dark chocolate.73

Therefore, the consumption of coffee and tea influences diurnal BP variation by causing a transient BP elevation. However, their effects on mean 24-h BP are small, and chronic tea consumption might act to protect against hypertension. Cocoa and chocolate appear to reduce casual and 24-h BP in hypertensive patients.

Influence of bathing

Taking a hot bath influences BP and its diurnal variation. BP usually rises at the beginning of bathing, then decreases during hot bath immersion, falls further immediately after bathing and then gradually returns toward the baseline level. These changes are physiological responses to high temperature and water immersion.

The post-bathing hypotension may be profound and lasts for about 1 h. Kawabe et al.74 studied the influence of bathing on home BP and observed a significant reduction in BP at 30 min and 31–60 min, but not at 61–120 min after bathing. They have also shown that post-bathing measurement of home BP is an independent determinant of a large morning–evening BP difference.75

Therefore, bathing results in BP reduction for a certain period. Post-bathing hypotension might be particularly pronounced in Japanese because many Japanese use deep bathtubs and a high water temperature for bathing.


Behavioral factors have an important role in diurnal BP variation. The diurnal changes in BP are closely related to mental and physical activities. Mental and physical stress elevates BP in the morning and during the daytime and may cause morning and daytime hypertension. Sleep disturbance elevates nighttime BP and may be responsible for nondipping. Obesity and excess sodium intake may cause a greater rise in nighttime BP than daytime BP in sensitive subjects. Alcohol consumption increases BP during the daytime, particularly in the morning, with little change in mean 24-h BP. Cigarette smoking increases daytime BP without altering nighttime BP. Coffee and tea consumption elevate BP for a short period but their effect on 24-h BP is small. Understanding these changes in BP caused by behavioral factors is important and leads to better management of hypertension. It should also be mentioned that exercise, food intake, alcohol ingestion and bathing cause subsequent BP reduction, especially in susceptible individuals.