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BLOG: August 2009

Unhealthy habits - whistling past the graveyard?

Everyone is talking about the importance of healthy lifestyle for sustaining health. But how much those typical unhealthy habits - like excess body weight, junk foods, smoking or lack of exercise - really hurt? A recent CDC (Centers for Disease Control) study comes up with some specific numbers for these four main offenders.

The study - Healthy Living Is the Best Revenge, by Ford et al (Archives of Internal Medicine, 8/2009) - analyzed data from 23,153 German participants aged 35 to 65 years from the European Prospective Investigation Into Cancer and Nutrition–Potsdam study. Within a mean follow-up period of 7.8 years, nearly 10% of participants developed  chronic disease: 3.8% cancer, 3.7% diabetes, 0.9% myocardial infraction and 0.8% stroke (the four events that the study had focused on). Among those, little over 0.5% of the total had two of these events.

To find out how much unhealthy habits contributed to new diseases, the authors defined four specific criteria for healthy lifestyle habits:

 1  never smoked

 2  body mass index below 30 (weight in kg per height in m as kg/m2

 3  3.5 hours, or more, of physical activity a week, and

 4  healthy diet (high vegetables, whole grain and fruit intake)

and looked at the incidence rates within five groups formed based on these healthy lifestyle factors: a group with not a single healthy factor, with one, two, three, or all four of them.

Turned out, they do matter. The final adjusted risk ratio for developing one of these four disease events was 4.5 times lower for those having all four factors vs. those having none. Specifically, the relative hazard ratios ranged from 1 for those without a single of these four health factors, to 0.51 for those with any one of them, 0.37 with any two, 0.28 with three, and 0.22 with all four.

Even a single healthy lifestyle factor cuts the risk from these diseases in half - by 49%. The benefit grows steadily, but at a slower rate, as we replace more unhealthy habits with healthful ones. So, if you were wondering whether a single lifestyle change can have much of an impact,

the answer seems to be a resounding "yes".

The drop in risk ratio with even a single healthy habit is particularly obvious with diabetes. A single healthful factor out of these four cuts the risk down to one third. With all four the risk of developing diabetes is fourteen times lower.

For myocardial infraction, a single factor reduced the risk by 40%, while with all four it is nearly six times lower. The gain was less dramatic for cancer and stroke, with nearly 50% and 35% risk reduction with all four healthy lifestyle factors, respectively.

A single factor most strongly correlated with the incidence of a disease was body mass index in diabetes. Those with the index value below 30 were nearly three times less likely to develop diabetes than those not smoking, exercising or eating generally healthy diet. Similar, although less strong correlation was between smoking and myocardial infraction; those that never smoke had nearly half the incidence compared to those practicing regular exercise, having body mass index below 30, or eating healthfully (the latter being the least protective in this respect).

And keep in mind that these gains are for a period of less than 8 years; it is to expect that they become even more significant for longer periods of time.

These results are consistent with those of other similar studies:

sixfold reduction in coronary heart disease in woman practicing a low-risk lifestyle (not smoking, body mass index below 25, low alcohol consumption, at least half an hour of moderate to vigorous exercise a day, and specific dietary requirements - increased intake of cereal fiber, marine omega-3 fatty acids, and folate; increased ratio of polyunsaturated fats to saturated fats; and low trans fat intake and glycemic load) in the Nurses Health Study (Stampfer et al, 2000), within 14 years of follow-up; in the same study, risk of developing diabetes was 11 times lower for those practicing healthy lifestyle

Healthy Aging: a Longitudinal Study in Europe (Knoops et al, 2004) found 65% mortality reduction for elderly folk with all healthy lifestyle factors that the study focused on (Mediterranean diet, moderate alcohol use, physical activity and no smoking)

55% lower risk of suffering stroke in Women's Health Study (Kurth et al, 2006) for those scoring higher on lifestyle health factors (smoking, alcohol use, body mass index, exercise and diet), within 10 years of follow-up

nearly eightfold reduction in the risk of coronary heart disease in the Health Professionals Follow-up Study (Chiuve et al, 2006), for those with all five lifestyle health factors (healthy diet, low alcohol use, no excess body weight, no smoking, regular physical activity), within over 16 years of follow-up

40% lower all-cause mortality and 35% lower cardio-vascular disease incidence within 4 years of follow-up in the Atherosclerosis Risk in Communities Study (King et al, 2007), with four lifestyle health criteria defined as eating 5 or more fruits and vegetables per day, exercising 2.5 hours a week or more, having a body mass index between 18.5 and 30.0, and not smoking

14 years longer life, on average, for those with all four vs. only one of healthy lifestyle factors (not smoking, not physically inactive, moderate alcohol use and vitamin C plasma level above 0.88mg/dL) in the EPIC-Norfolk study (Khaw et al, 2008), and

threefold and fivefold lower risk of stroke for men and women, respectively, who practiced a low-risk lifestyle (not smoking, 30 minutes or more of moderate to vigorous exercise a day, diet score in the top 40%, low alcohol consumption and body mass index below 25) in the  Health Professionals Follow-up Study (Chiuve et al, 2008), within 20 and 18 year follow up for men and women, respectively

Obviously, there is no lack of specific, real-life numbers to support the notion that a few notoriously known unhealthy lifestyle habits significantly increase the risk of both, falling ill and premature death. Yet, as the published commentary to the study points out, nearly half of all deaths in this country are premature, and most of those are caused by only 3 lifestyle factors:

smoking, poor dietary habits (including obesity)
and physical inactivity.

Despite their ill effect on health being generally well known, this hasn't changed significantly in the decade from 1994 to 2004, and is not likely to change in 2014. Not for the better, anyway. A recent study (King et al, Adherence to Healthy Lifestyle Habits in US Adults, 1988-2006, AJM 6/2009) has found that unhealthy habits become more, not less widespread. In 2006, only 26% of Americans consumed 5 or more servings of vegetables and fruit per day, compared to 43% in 1988.

The percentage of population with excess weight went from 28% in 1988 to 34% in 2006.

The segment of the American public adhering to 5 healthy lifestyle habits - healthy weight, plant-rich diet, regular physical activity, not smoking and moderate-to-low alcohol intake - has plummeted from 15% in 1988 to 8% in 2006.

People are, of course, free to set their priorities. But if you stop for a minute to think of how much these petty unhealthy habits can and do take away - it's just not worth it.