Lifestyle strongly influences many elements of health. Regular physical activity, smoking cessation, and appropriate intake of energy, fluids, and macro- and micronutrients can prevent many chronic conditions, improve function, and increase quality of life. However, over time, a positive energy balance due to sedentary lifestyle and excess energy intake leads to obesity, especially increased visceral fat deposits. Visceral obesity, which is prevalent in the elderly, is an important risk factor for hypertension, type 2 diabetes, and dyslipidaemia. In turn, obesity and its complications are risk factors for nephropathy and chronic kidney disease (CKD).

The human life span is also associated with long-term exposure to environmental and behavioural factors. Thus, the effects of adverse behaviors on health increase with aging. Although many lifestyle-related risk factors are modifiable, changing behaviors can be difficult. Moreover, little evidence exists to show that lifestyle modification decreases the risk for CKD and improves kidney outcomes. It is particularly difficult to demonstrate the effect of modifying lifestyle-related risk factors on renal function, because some damage (e.g., endothelial dysfunction and arteriosclerosis) is irreversible.

This review summarizes the current knowledge concerning the effects of lifestyle and its modification on the occurrence and progression of CKD, focusing on the elderly population.

The recently completed PolSenior study analyzed fluid intake in an elderly Polish population (1). The results showed that inadequate fluid intake (< 1000 ml/day) is more common with increasing age (13.3% at 65-69 years vs. 26.5% at > 90 years) and more common among women than men (25.3% vs. 19.4%). Inadequate fluid intake can reduce the glomerular filtration rate (GFR), which may partially explain the greater prevalence of low estimated GFR (eGFR) (< 60 ml/min/1.73 m²) among women (2). The results of the PolSenior study revealed that 96.8% of elderly subjects who met the criteria for CKD were unaware they had the disease (2).

In daily clinical practice, physicians recommend generous fluid intake (≥ 4 l/day) for patients with CKD, with higher fluid intake for patients with higher serum creatinine levels. However, direct evidence for the association between adequate fluid intake and better kidney performance is lacking (3). Indirect evidence for this recommendation includes the results of two cross-sectional studies performed in different populations. These studies showed that increasing fluid intake was associated with a lower risk of CKD (defined as eGFR < 50 ml/min). Participants with the highest quintile of fluid intake (3.2 l/day) had the lowest risk (odds ratio [OR] = 0.50, 95% confidence interval [CI] 0.32-0.77) (4).

Better documented is the effect of dehydration on kidney function. Dehydration is an important risk factor for acute kidney injury. Adequate fluid intake may be even more important for individuals with undiagnosed CDK.

Although there is no evidence that alcohol consumption impairs renal function, heavy drinkers may experience repeated episodes of acute kidney injury caused by dehydration (5). These episodes may induce or exacerbate interstitial kidney fibrosis. Studies analysing the relationship between moderate or heavy drinking and CKD have reported conflicting results. Several studies found that moderate alcohol consumption was not associated with renal dysfunction (6, 7). For example, a 14-year prospective study of 11 023 initially healthy men showed that those who consumed two to six drinks per week had a risk for serum creatinine elevation (> 133 μmol/L) similar to that of men who consumed no more than one drink per week (6). Similarly, results of the Australian Diabetes, Obesity, and Lifestyle (AusDiab) study (8) showed that moderate drinking decreased the risk of de novo development of renal function impairment (eGFR < 60 ml/min/1.73 m2) in both men (OR = 0.34, 95% CI 0.22-0.59) and women (OR = 0.68, 95% CI 0.36-1.27). Funakoshi et al. recently reported that the prevalence of CKD is 40% lower in daily drinkers than in non-drinkers among professionally active men (9). In addition, Schaeffner et al. (6) found that consuming at least seven drinks per week had a beneficial effect on kidney function (OR = 0.71, 95% CI 0.55-0.92). In contrast, Shankar et al. reported that frequent alcohol consumption (> four drinks per week) increased the risk for CKD (OR = 1.99, 95% CI 0.99-4.01) in 5-year longitudinal analysis of 3.392 Americans without CKD (10). Additionally, Perneger et al. reported a higher prevalence of drinkers among patients with end-stage kidney disease than in age-matched controls (11).

The above-mentioned studies did not all focus on the elderly; however, results obtained in younger populations should be generalizable to the elderly population. Results of the PolSenior study show that 17.1% of the elderly Polish participants (men 27.0%, women 6.9%) reported frequent or very frequent alcohol consumption (12). Frequent alcohol consumption is associated with a lower risk for impaired kidney function (eGFR < 60 ml/min/1.73 m²) in the elderly Polish population (22.4% vs. 36.5% of those who abstained from drinking) (13).

Smoking is another known risk factor for CKD. A number of pathophysiological links between smoking and kidney damage have been identified, including the promotion of renal atherosclerosis (14), alterations in systemic and renal hemodynamics (15), and endothelial dysfunction (16). The relationship between smoking and end-stage kidney disease was initially shown in a longitudinal study of diabetic patients (17). A study by Biesenbach et al. reported that the rate of GFR loss was twice as high in smokers as in non-smokers (18).

The National Health and Nutrition Examination Survey II (NHANES II) reported that individuals who smoked > 20 cigarettes/day had a 2.3-times higher risk for CKD (7). In the AusDiab study, smoking was significantly associated with renal impairment in men (OR = 3.59) but not in women (19). In this study, lifetime exposure, but not current level of smoking, was related to lower eGFR (19).

Smokers may also have an increased risk of albuminuria. In the general Korean population, smoking was associated with a 38% higher risk for albuminuria (as assessed by urine dipstick) (20). Pinto-Sietsma et al. observed a 65% higher risk of low-grade albuminuria in smokers (21). Some studies have suggested that men are more vulnerable to develop albuminuria than women (22, 23). Haroun et al. estimated the risk of CKD attributable to cigarette smoking in a population-based study as 31% (24). However, CKD risk related to smoking in the elderly population should be greater, because of long-term exposure to smoke along with other factors that lead to kidney injury.

There is no doubt that smoking cessation improves overall health. Smoking cessation may also specifically benefit the kidneys. For example, the rate of GFR loss among former smokers is lower than that of current smokers (25). Moreover, eGFR decline is more rapid among current smokers (-1.79 ± 0.35 ml/min/y) compared with former smokers (-1.54 ± 0.37 ml/min/y) (26). However, it has not yet been demonstrated that smoking cessation significantly improves kidney performance in elderly populations.

NHANES III reported that, compared with elderly individuals without CKD, those with CKD were more likely to be physical inactive (28.0% vs. 13.5%) and disabled (23.9% vs. 17.6%), defined as having difficulty with performing the activities of daily living (27, 28). However, the cross-sectional study design precluded the establishment of causality. Similar findings were obtained in a study carried out in the United Kingdom, where low eGFR (< 45 ml/min/1.73 m²) was associated with impaired functional status (i.e., partial dependence on activities of daily living and lack of physical activity) in the elderly population (29). The effect of physical inactivity on mortality was similar between groups (CKD and non-CKD) (27).