Obesity and hip osteoarthritis: the weight of the evidence is increasing

[Guest guest]

Hi All, Here is another reason for doing CR: Obesity and hip

osteoarthritis: the weight of the evidence is increasing. We are getting

older as a nation and this disease makes life tough. I have the genetic

predisposition. It affects ladies especially.

Cheers, Al.

Gelber AC.

Obesity and hip osteoarthritis: the weight of the evidence is increasing.

Am J Med. 2003 Feb;114(2):158-9. No abstract available.

PMID: 12586240 [PubMed - in process]

Osteoarthritis affects about 20 million people in the United States [1], with

a predilection for

particular joint sites in the peripheral skeleton, predominantly the hands,

knees, and hips.

Osteoarthritis results in substantial morbidity and disability in the

elderly, and it is the leading

indication for the more than 200,000 knee and hip replacement surgeries

performed annually in the

United States [2]. Notwithstanding the substantial disease burden and the

effects on quality of life,

there is no curative therapy for osteoarthritis. Conventional treatment

reduces symptoms and

improves function [3] but does not alter the disease process. Once

structural damage to articular

cartilage occurs, with joint space narrowing and osteophyte formation, these

pathologic changes

cannot be reversed by standard therapeutic modalities. Hence, much attention

has been invested in

improving our understanding of the epidemiology of osteoarthritis and in

elucidating which factors

predispose to the development of this disorder.

Risk factors for osteoarthritis include those that are fixed (e.g., age,

sex, family history, and,

possibly, race), as well as those that are amenable, if not in practice,

then at least in principle, to

modification (e.g., overweight or obesity, physical activity, exercise

levels, muscle weakness, and

joint injury). To date, the link between overweight or obesity and

osteoarthritis has been strongest

and most consistently demonstrated for knee osteoarthritis. With regard to

the hip joint,

epidemiologic data linking obesity with osteoarthritis have been

inconsistent. In one population

survey from the United States [4], obesity was not associated with

unilateral hip osteoarthritis. In

contrast, studies from the United Kingdom [5] and Sweden [6 and 7] reported

a positive relation

between obesity and hip osteoarthritis. More recently, greater weight and

body mass index were

associated with a higher incidence of symptomatic hip osteoarthritis in a

health plan group [8]. Thus,

there is increasing evidence suggesting the deleterious role of overweight

and obesity in hip

osteoarthritis.

Before accepting that increased body weight is a risk factor for hip

osteoarthritis, one needs to

consider the possible methodologic limitations of the conducted studies. In

a recent review [9],

relatively few reports were identified from which to infer causality between

weight and osteoarthritis.

Moreover, only 12 studies, including those cited above, met the eligibility

criteria for inclusion in the

review. They comprised one cohort study, four case-control studies, and

seven cross-sectional

studies. However, cross-sectional surveys are limited by ascertainment of

exposure and outcome

status at the same point in time. Case-control studies may exaggerate the

risk of osteoarthritis

associated with prior weight because patients with symptomatic hip

osteoarthritis may be more

likely to overestimate earlier body weight. In contrast, prospective cohort

studies determine

exposure (obesity) status before the outcome (hip osteoarthritis) develops.

It is in this context that

the report of Karlson et al. [10], which appears in this issue of the

Journal, needs to be recognized.

Using data from the Nurses' Health Study, a prospective cohort study of more

than 120,000

women, Karlson et al. found that only higher body mass index and older age

were associated with

an increased risk of osteoarthritis requiring hip replacement surgery [10].

In particular, women in the

highest category of body mass index had a twofold greater risk of hip

arthroplasty, compared with

those in the lowest category.

Strengths of their report include the high (>90%) response rate to the

biennial questionnaires and the

subanalyses to verify the face validity of the outcome. However, the study

excluded women with

cardiovascular disease, which, given that cardiovascular disease risk

factors are highly prevalent

among U.S. adults with osteoarthritis [11], may have narrowed the

generalizability of the findings. In

addition, it is not clear if the weights used to calculate body mass index

were obtained at cohort

inception (in 1976), or if they were obtained from the 1990 biennial

questionnaire (the baseline year

for the analyses). If the later values were used, the associated analyses do

not allow for a substantial

period of time to have elapsed between ascertainment of exposure and

development of outcome, as

it would had the investigators utilized weight at cohort entry and incident

arthroplasty 14 or more

years later. In a related fashion, self-reported weight at age 18 years was

collected in 1980, when

the age range of the cohort was 34 to 59 years. Recalled, rather than

actual, weight at age 18 years

was used in these analyses; in a separate validity study, these recalled

weights correlated strongly

with recorded weight in medical records.

A particularly intriguing finding by Karlson et al. was the relation of body

mass index at age 18 years

to the risk of hip osteoarthritis [10]. Moreover, risk estimates at age 18

years were significantly

greater than those for " recent " body mass index, which were reported closer

to the date of surgery.

This finding complements a previous study that similarly examined the

relation of body weight in

young adult life to the incidence of hip osteoarthritis among health

professionals [12]. This other

study, however, involved male physicians, and did not find evidence of a

link between body weight

in the third decade of life and hip osteoarthritis in later life.

It has been estimated that if obesity were eliminated, the prevalence of hip

osteoarthritis would

decrease by 25% [13]. Thus, weight modification could lead to a substantial

reduction in the burden

of osteoarthritis in weight-bearing joints. The findings by Karlson et al

clearly strengthen the

argument that greater body weight increases the risk of hip osteoarthritis

that is severe enough to

warrant replacement surgery, as well as support the position that prevention

of osteoarthritis should

begin early in life, before the onset of joint pain and before function is

compromised.

References

1. R.C. Lawrence, C.G. Helmick, F.C. Arnett et al., Estimates of the

prevalence of arthritis and

selected musculoskeletal disorders in the United States. Arthritis Rheum 41

(1998), pp. 778–799.

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2. W.H. and C.B. Sledge , Total hip and total knee replacement. N

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3. Recommendations for the medical management of osteoarthritis of the hip

and knee: 2000

update. American College of Rheumatology Subcommittee on Osteoarthritis

Guidelines. Arthritis

Rheum 43 (2000), pp. 1905–1915.

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10. E.W. Karlson, L.A. Mandl, G.N. Aweh et al., Total hip replacement due to

osteoarthritis: the

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SummaryPlus | Full Text + Links | PDF (82 K)

11. G. Singh, J.D. , F.H. Lee et al., Prevalence of cardiovascular

disease risk factors among

US adults with self-reported osteoarthritis: data from the Third National

Health and Nutrition

Examination Survey. Am J Manag Care 8 suppl (2002), pp. S383–S391.

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12. A.C. Gelber, M.C. Hochberg, L.A. Mead et al., Body mass index in young

men and the risk of

subsequent knee and hip osteoarthritis. Am J Med 107 (1999), pp. 542–548.

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13. D.T. Felson and Y. Zhang , An update on the epidemiology of knee and hip

osteoarthritis with a

view to prevention. Arthritis Rheum 41 (1998), pp. 1343–1355.

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