Adherence to Healthy Lifestyle Habits in US Adults, 1988-2006

Methods 

The study was a comparative analysis of middle-aged adults aged 40-74 years participating in the NHANES III 1988-1994 and 2001-2006, national data sets that are available for public use. The study was reviewed by the Institutional Review Board of the Medical University of South Carolina and was exempt. The study populations and study variables were matched to be as identical as possible in the 2 data sets. Below is a description of the population and study variables from each of the surveys.

Results 

Over the last 16 years, the percent of adults aged 40-74 years with a BMI ≥30 has increased from 28% to 36% (P <.05); physical activity 12 times a month or more has decreased from 53% to 43% (P <.05); smoking rates have not changed (26.9% to 26.1%); eating 5 or more fruits and vegetables a day has decreased from 42% to 26% (P <.05); and moderate alcohol use has increased from 40% to 52% (P <.05). Adherence to all 5 healthy habits as a group has gone from 15% to 8% (P <.05).

Comparing men and women (Table 1), men's healthy habits have decreased more than women in some areas; men's physical activity at 12 times a month or more has decreased from 57% to 43%, and eating ≥5 fruits and vegetables a day has decreased from 45% to 26% (both P <.05) Women's physical activity frequency also decreased, from 49% to 43%; women's eating of ≥5 fruits and vegetables decreased from 39% to 25% (P <.05). The prevalence of obesity climbed to a similar degree in both men and women. Moderate alcohol intake increased more in women than men; the percentage of smokers was unchanged in both men and women (Table 1).

Table 1. Characteristics of Adult Men and Women Ages 40-74 Years

		NHANES III				NHANES 2001-2006
		Men	Women	Totals	χ2P-Value⁎	Men	Women	Totals	χ2P-Value⁎
	BMI (kg/m2) (%)				<.01				.02
	<30	74.8	70.2	72.4		66.2	61.8	64.0
	≥30	25.2	29.8	27.6		33.8	38.2	36.0
	Physical activity (%)				<.01				.02
	None	10.5	19.5	15.2		34.0	38.1	36.1
	1-12 times/month	32.5	31.5	31.9		22.7	18.6	20.6
	>12 times/month	57.0	49.0	52.8		43.3	43.2	43.3
	Smoking (%)				<.01				<.01
	Yes	32.3	22.0	26.9		31.0	21.1	26.0
	No	67.7	78.0	73.1		69.0	78.9	74.0
	Fruit/Veg (%)				<.01				.44
	<5 servings/day	54.8	61.0	58.0		73.5	75.2	74.4
	≥5 servings/day	45.2	39.0	42.0		26.4	24.8	25.6
	Alcohol (%)				<.01				<.01
	None	40.0	61.9	51.5		32.6	47.4	40.1
	Moderate	49.8	31.5	40.2		57.2	45.9	51.5
	Exceeds moderate	10.2	6.6	8.3		10.1	6.7	8.4
	Healthy habits (%)				.16				.09
	None	0.4	0.2	0.3		0.9	0.3	0.6
	One	4.0	4.1	4.0		8.2	6.0	7.1
	Two	19.2	19.7	19.4		26.9	27.4	27.1
	Three	29.2	32.4	30.9		31.4	32.6	32.0
	Four	31.4	28.9	30.1		24.5	24.8	24.6
	Five	15.8	14.6	15.2		8.2	8.8	8.5

NHANES=National Health and Nutrition Examination Survey; BMI=body mass index.

⁎ Males vs females.

Table 2 compares healthy habits adherence according to race, characterized as non-Hispanic white, non-Hispanic black, and Hispanic. Although Non-Hispanic whites have lower rates of obesity, all races have experienced increases in obesity rates since 1988-1994 (Table 2). Non-Hispanic whites participate in physical activity more frequently, but racial differences have narrowed in this category over time. Rates of eating 5 or more fruits and vegetables daily have decreased since 1988-1994, from 44% to 25% among non-Hispanic whites, to the point that they are now comparable to the other groups (Non-Hispanic blacks 31% to 25%, Hispanics 37% to 29%). Moderate alcohol consumption has increased 10%-12% among all comparison groups. Non-Hispanic whites have decreased by the greatest absolute percentage in overall adherence to all 5 healthy lifestyle habits during the study period, from 17% doing all 5 to 9%, while non-Hispanic blacks have gone from 6% to 4%, and Hispanics have decreased from 9% to 4%.

Table 2. Characteristics of Adults by Race Ages 40-74 Years

		NHANES III				NHANES 2001-2006
		NHW	NHB	HISP	χ2P-Value⁎	NHW	NHB	HISP	χ2P-Value⁎
	BMI (kg/m2) (%)				<.01				<.01
	<30	73.9	64.3	66.5		64.6	57.0	66.1
	≥30	26.1	35.7	33.5		35.4	43.0	33.9
	Physical activity (%)				<.01				<.01
	None	12.8	28.4	25.5		33.1	49.1	48.0
	1-12 times/month	32.0	30.4	33.6		21.7	16.3	15.7
	>12 times/month	55.3	41.2	40.9		45.2	34.6	36.2
	Smoking (%)				<.01				<.01
	Yes	26.2	36.6	22.3		24.8	34.4	27.1
	No	73.8	63.4	77.7		75.2	65.6	72.9
	Fruit/vegetables (%)				<.01				.28
	<5 servings/day	56.3	68.8	62.9		74.6	75.4	71.3
	≥5 servings/day	43.7	31.2	37.1		25.4	24.6	28.6
	Alcohol (%)				<.01				<.01
	None	49.9	61.6	55.8		38.2	51.0	44.8
	Moderate	41.6	30.8	37.3		53.2	41.3	48.6
	Exceeds moderate	8.5	7.7	6.9		8.7	7.7	6.6
	Healthy habits (%)				<.01				<.01
	None	0.3	0.5	0.3		0.7	0.4	0.2
	One	3.8	6.1	4.2		6.6	11.5	6.2
	Two	18.1	28.8	22.3		27.2	27.8	26.2
	Three	29.8	35.9	35.7		30.8	38.6	35.3
	Four	31.2	22.6	28.2		25.3	17.3	27.6
	Five	16.8	6.2	9.4		9.5	4.4	4.5

NHANES=National Health and Nutrition Examination Survey; NHW=non-Hispanic white; NHB=non-Hispanic black; HISP=Hispanic; BMI=body mass index.

⁎ Differences by race.

Individuals with cardiovascular disease, diabetes, hypertension, or hypercholesterolemia were evaluated to determine whether such individuals were adhering to the healthy habits to a greater or lesser degree than people without those conditions, and whether adherence had changed over time. The frequency of these conditions has increased from 1988-1994 to 2001-2006 (Table 3). Adherence to healthy habits has decreased over time in individuals with these risk conditions, as it has for people without them (P <.05). People with cardiovascular disease or risk factors were compared with those without such risk factors, and individuals with risk factors did not adhere to a healthy lifestyle pattern at a higher rate than people without such risk in either analysis period (Table 4). Adherence to all 5 healthy habits has decreased over time in individuals with each of these risk conditions (P <.05).

Table 3. Prevalence of Diagnosed Cardiovascular Disease (CVD) and Risk Conditions

		NHANES III	NHANES 2001-2006
	Diagnosed CVD (%)	8.1	10.4
	Diagnosed diabetes (%)	7.9	10.5
	Diagnosed hypertension (%)	33.0	37.1
	Diagnosed high cholesterol (%)	30.2	37.7

Table 4. Healthy Habit Characteristics of Adults by Health Condition Ages 40-74 Years

		Healthy Habits (%)
		None	One	Two	Three	Four	Five	χ2P-Value
	NHANES III
	Diagnosed CVD	0.1	6.6	24.2	31.7	26.4	11.0	<.01
	Diagnosed diabetes	0.5	4.8	26.8	34.1	24.7	9.0	<.01
	Diagnosed hypertension	0.8	5.6	23.4	31.5	27.0	11.7	<.01
	Diagnosed high cholesterol	0.1	3.4	16.9	30.8	32.4	16.3	<.01
	No CVD or risk condition	0.15	3.7	18.2	30.0	31.3	16.7	.02
	NHANES 2001-2006
	Diagnosed CVD	0.9	9.1	36.5	30.2	16.4	6.9	.01
	Diagnosed diabetes	0.5	9.2	36.6	34.4	15.7	3.5	<.01
	Diagnosed hypertension	1.0	7.2	32.5	34.0	20.4	4.9	<.01
	Diagnosed high cholesterol	0.5	6.5	27.1	32.8	25.7	7.5	.30
	No CVD or risk condition	0.4	6.7	25.1	29.7	26.6	11.4	<.01

NHANES=National Health and Nutrition Examination Survey; CVD=cardiovascular disease.

Discussion 

Generally, adherence to a healthy lifestyle pattern has decreased during the last 18 years; adherence to all 5 healthy habits as a group has gone from 15% to 8% (P <.05). Men overall and non-Hispanic whites (both men and women) have a pattern of declining adherence to a healthy lifestyle that exceeds their respective comparison groups. Of equal or greater concern is the finding that individuals with cardiovascular disease, hypertension, diabetes, or hyperlipidemia do not adhere to a healthy lifestyle any more frequently than people with no such conditions. Perhaps not surprisingly, the prevalence of diabetes, hypertension, obesity, and cardiovascular disease all have increased since 1988-1994 (Table 3). The decrease in healthy habits seen in this study is consistent with previous reports of increasing obesity17 and has broad implications for the future acceleration of risk of diabetes, hypertension, and cardiovascular disease in middle-aged and older adults.

The incidence of many diseases, including diabetes, cardiovascular disease, and cancer, are related to lifestyle factors.18, 19 Physical inactivity, inadequate intake of fruits and vegetables, smoking, and obesity contribute a large measure to the morbidity and mortality from cardiovascular disease, and are the underlying cause of premature death in cardiovascular and other diseases.1, 20, 21 Thus, decreasing adherence to healthy habits will undoubtedly have a negative impact on the future incidence of premature death and disease.

In addition, trends over a similar time period as the current study indicate a worsening of health-related quality of life and self-rated health.22, 23 Physical inactivity, smoking, and obesity are closely linked to depression24 and lower quality of life. Conversely, increasing adherence to healthy habits is associated with improved quality of life in people with diabetes.25

Reasons for the decrease in healthy lifestyle habits are complex, but may include societal attitudes of the importance of a healthy diet and physical activity, sex differences in willingness to change, and generally low self-assessments of cardiovascular risk despite statistical evidence to the contrary.26 Another factor contributing to the greater decrease in men may be that men are less willing to accept health advice from dietitians, counselors, and nurses than women, likely making it more difficult to expect an improvement in the healthy habits using common strategies.27 This “help-denial” syndrome may lead to the poorer adherence to healthy habits seen in the current study along with poorer control of risk factors such as hypertension.28 Finally, reliance on labor-saving devices and use of automobiles instead of walking/biking to work may be taking a toll on average daily physical activity patterns.29

This study has important implications regarding public health. The finding that adherence to all 5 healthy lifestyle habits has decreased from 15% to 8%, despite increases in moderate alcohol consumption, demonstrates that the amount of emphasis by the current health system on prevention and healthy lifestyles may be insufficient. The implications of the decreasing rates of healthy lifestyle habits include the possibility of an upswing in cardiovascular morbidity and mortality, and increase in the number of aging persons with disability and decreased quality of life due to the burden of chronic disease.30 In addition, future health care costs are likely to continue to increase if middle-aged adults do not increasingly adopt a healthy lifestyle as the primary approach to prevention and treatment of hypertension, diabetes, and hyperlipidemia.

The study has limitations that should be mentioned. As in other epidemiologic studies, misclassification is a concern. In the NHANES II study, a 24-hour food recall questionnaire was used that specifically asked about average intake of fruits and vegetables, and in the 2001-2006 survey, a food frequency questionnaire was used. However, while these 2 methods vary by less than ±0.1 servings per day, there is some bias possible with either of these methods.31 In addition, an optimally healthy diet has other characteristics, including adequate fiber intake, low fat intake, and optimizing sodium, magnesium, and several other nutrients, but these factors were not assessed in the current investigation.4, 7, 8

Another limitation is that physical activity habits in the NHANES survey are from patient self-report and could thus be inaccurate or biased. While there is no suitable measurement instrument or study analysis design that is suitable for all situations,32 several studies have demonstrated that middle-aged people are likely to have a fairly stable physical activity pattern over their middle years, thus indicating internal consistency and a reduced opportunity for bias.2, 33, 34, 35

What actions are needed to counteract the decrease in healthy habits among US adults aged 40-74 years at a time of life when they are increasingly vulnerable to developing cardiovascular disease? A recent study used the Archimedes model to evaluate the impact of comprehensive prevention activities on cardiovascular morbidity, mortality, and costs among adults aged 20-80 years.36 According to the study, 78% of adults aged 20-80 years are candidates for at least one prevention activity. If everyone received the activities for which they are eligible, myocardial infarctions and strokes would be reduced by approximately 63% and 31%, respectively.36 Using more realistic assumptions regarding reachable levels of adherence, myocardial infarctions and strokes could be reduced approximately 36% and 20%, respectively. Despite this improvement in cardiovascular disease rates, only smoking cessation was a long-term cost-saving strategy according to the study; this result is partly because people who die early do not cost the system dollars.

The potential public health benefits from promoting a healthier lifestyle at all ages, and especially ages 40-74 years, are substantial. Regular physical activity and a prudent diet can reduce the risk of premature death and disability from a variety of conditions including coronary heart disease, and are strongly related to the incidence of obesity.37, 38 In the US, medical costs due to physical inactivity and its consequences are estimated at $76 billion in 2000 dollars.39 Research indicates that individuals are capable of adopting healthy habits in middle age and making an impact on cardiovascular risk.2, 40

The current study demonstrates that adherence to 5 modest healthy habits among adults aged 40-74 years is low and has decreased over the last 18 years. These findings should provide new motivation for an increasing commitment to promoting healthy lifestyles for the public good.